# Facets in my 16 TPI Threads - Need some help!



## TX COWDOC

Happy New Year - 
I've spent the last 2 days troubleshooting an irregular finish to my 16 TPI threading with my PM1236 (Single Phase Baldor). I received the lathe in July and it has taken me several months to finally get to a point where I was able to practice threading. I thought I was going to build a 6.5 PRC this week but obviously not until I get this resolved.   I'm using ISCAR SER 0625 H16 RH threading tool in an Aloris BXA holder.    Bits are ISCAR 16ER AG 60 IC908.  Lathe settings are appropriate for the 16 TPI.  Feed rates on the compound are per the ISCAR 16TPI charts.  I've tried 2 different chucks (6 jaw and 3 jaw), 2 different materials (round stock from McMaster in Aluminum and Steel). I've tried different tool heights. 

I'm hoping there is an answer to what is causing this issue.  I will be emailing Precision Matthews for technical support as well.  Thank you in advance for your help.


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## Aukai

Single phase 60 cycle impressions?


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## Lo-Fi

The ISCAR charts may well be for a much more rigid CNC setup. They look like classic chatter marks to me. Try a less aggressive feed and different speeds. 

Are you infeeding with the compound set slightly less than half the included angle, or straight in?


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## Batmanacw

Are you above center? Or right on?


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## TX COWDOC

Lo-Fi said:


> The ISCAR charts may well be for a much more rigid CNC setup. They look like classic chatter marks to me. Try a less aggressive feed and different speeds.
> 
> Are you infeeding with the compound set slightly less than half the included angle, or straight in?


65 RPM (which is the slowest setting on the PM1236).  Compound only.


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## TX COWDOC

Batmanacw said:


> Are you above center? Or right on?


As close to perfect as I can make it.  Also repeated it with a slightly lower than center setting.


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## TX COWDOC

I have the impression that the chatter is visible in the turned and faced surfaces in my pictures as well.  ?


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## Batmanacw

When you feed in at 29.5° you should only be cutting on the left side of the insert so the other side of the thread shouldn't have chatter. There should be a difference.


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## danallen

I agree that it looks like chatter. Are you feeding the tool straight in or at 29.5 degrees with the compound? I also agree the insert may not be ideal for the lathe. Do you have a HSS blank you could grind into a threading tool? I would try that and feed at 29.5 degrees in small increments and take a .001 finish cut straight in and then repeat the cut without advancing the tool.


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## TX COWDOC

I'm feeding on the compound at 29.5 degrees.  Not sure how well I will do grinding a 60 deg threading tool.


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## Liljoebrshooter

Is that tool that much of a negative rake or just the picture makes it look like it?
My lathe threads much better with positive rake inserts.
Joe


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## TX COWDOC

Liljoebrshooter said:


> Is that tool that much of a negative rake or just the picture makes it look like it?
> My lathe threads much better with positive rake inserts.
> Joe





			https://www.mscdirect.com/product/details/60873023?orderedAs=SER+0625+H16&pxno=13296405&refnum=13296405&rd=k&tg=Recommendations&tpp=false&searchAhead=true&searchAheadTerm=ser%200625&typahddsp=SER%200625%20H16&hdrsrh=true
		





			https://www.mscdirect.com/product/details/85108983?fromRR=Y
		



Here's the tool I'm using.


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## Aukai

See post #13 for the possibilities of what I was thinking, 0n page 10 it gets resolved.








						Single Phase or 3-Phase?
					

This is not correct.  You lose horsepower with a static phase converter, not a VFD and not with a rotary phase converter.   Err, no::  A single phase motor has 3 windings (just like a 3-phase motor) and operates like a 3-phase motor but with the phases running 0 degrees, 180 degrees and 90...




					www.hobby-machinist.com


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## Liljoebrshooter

I can't see in the specifications for this tool holder or insert what the rake is.   I tried looking at the Iscar site but it won't load for me. 
Joe


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## TX COWDOC

Liljoebrshooter said:


> I can't see in the specifications for this tool holder or insert what the rake is.   I tried looking at the Iscar site but it won't load for me.
> Joe


This has positive rake.  Photo is not level.


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## Lo-Fi

I can see the photo in post #6 is not level, but judging by the angle against the top of the holder and the edge of the tool post it definitely looks like heavy negative rake which would require a _very_ rigid machine and explain the chatter you're experiencing.

You'll have much better results with positive rake tool, for sure.


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## rwm

This is very mysterious! Motor artifact? Chatter? Tool rake? Variable X?






Anxiously awaiting the solution.
R


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## Jubil

TX COWDOC said:


> I'm feeding on the compound at 29.5 degrees.  Not sure how well I will do grinding a 60 deg threading tool.



I agree with Danallen. Hss would probably help a lot and the tool is not hard to grind. You tube is a good place to look for “how to”. 

Chuck


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## davidpbest

TX COWDOC said:


> This has positive rake.  Photo is not level.


I can confirm.  I own this toolholder (and the Carmex which is almost identical) and this 16ER AG60 insert.  The toolholder sets the insert at negative 10-degree rake, but the insert itself has geometry that reverses that to a plus 3-degree rake at the cutting edge.  This is straight out of the book I'm about to publish on indexable tools for the lathe.






This is the toolholder from the Iscar catalog:





If the tools is hung-out or the compound cranked out past the swivel base, the tool will chatter on this size lathe - especially at low RPM's into aluminum.  The compound mount on this lathe is pretty flexible due to the postion of the t-nuts where the compound bolts to the cross slide when set at 30-degrees for threading.  OTOH, my guess is this could be harmonics from the single-phase motor which has been discussed here before.  Is there any evidence of this kind of chatter or waviness in surface finish with turning or facing tools?  Have you set a glass of water on top of the headstock and watched the ripples in the surface of the water when the lathe is running at this F/S?  That's usually a give-away for single-phase harmonic vibrations.


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## Aukai

The book is going to be a big help David


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## TX COWDOC

I'll check the glass of water / harmonics.  Thanks for all of the info.


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## erikmannie

TX COWDOC said:


> I'm feeding on the compound at 29.5 degrees.  Not sure how well I will do grinding a 60 deg threading tool.



If you have more money than time, you can buy preground tool bits. I use them.









						8 pc. Ground HSS Tool Bit Set 3/8" at Grizzly.com
					

<h1>H5687 8-Piece 3/8" HSS Tool Bit Set </h1> <p>Usually used on metal lathes, the H5687 tool bits can also be ground down and used for engraving metal. <p>This set comes with these sharpened profiles: offset right and left-hand tools with chip breaker, straight and ship breaker style treading...




					www.grizzly.com
				




Also, Accusize sells the same. Much less expensive on Amazon:



			https://www.amazon.com/gp/aw/d/B0779LLTC5/ref=ya_aw_od_pi?ie=UTF8&psc=1&th=1


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## TX COWDOC

erikmannie said:


> If you have more money than time, you can buy preground tool bits. I use them.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 8 pc. Ground HSS Tool Bit Set 3/8" at Grizzly.com
> 
> 
> <h1>H5687 8-Piece 3/8" HSS Tool Bit Set </h1> <p>Usually used on metal lathes, the H5687 tool bits can also be ground down and used for engraving metal. <p>This set comes with these sharpened profiles: offset right and left-hand tools with chip breaker, straight and ship breaker style treading...
> 
> 
> 
> 
> www.grizzly.com
> 
> 
> 
> 
> 
> Also, Accusize sells the same.


Thank you -  I may just try the HSS to rule out bit material.


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## erikmannie

TX COWDOC said:


> Thank you -  I may just try the HSS to rule out bit material.



I must like these because I just bought more of the 1/2” Accusize pre-ground HSS tool bits.


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## Larry$

Another vote for HSS. It really isn't very hard to grind. On bits that can be set very close to the tool holder, I use smaller blanks to save grinding effort. My tool holders will take 5/8" bits but my threading tool is just 3/8" and works fine. I thread at the highest speed that I feel comfortable with. I can do that because I thread away from the chuck. I don't fumble around moving both the compound and the cross slide. Unless you are cutting some huge threads or maybe Acme there is very little force on the lathe or the tool so letting the tool cut on both sides is no big deal. Eliminate compound issues by keeping it pulled back, no overhang and *locked*. I didn't develop this method. It's a Joe Pie thing. It works! 
OK, now it's the turn of all those who are opposed.


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## Z2V

TX COWDOC said:


> I'm feeding on the compound at 29.5 degrees.  Not sure how well I will do grinding a 60 deg threading tool.


Hey neighbor 
PM me an address and I’ll send you a 60* HSS tool to try


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## mikey

erikmannie said:


> Also, Accusize sells the same. Much less expensive on Amazon:
> 
> 
> 
> https://www.amazon.com/gp/aw/d/B0779LLTC5/ref=ya_aw_od_pi?ie=UTF8&psc=1&th=1



Wow, better read the reviews on those Accusize tool bits ... maybe better to grind your own?


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## davidpbest

If you need to use HSS because of limited feed/speed rates, but would prefer to use indexable tools instead of solid shank HSS, _*this kit from A.R Warner*_ is ideal.  The HSS On-Edge (vertical V-shape) inserts are available in neutral and positive rake.  I love this kit for threading softer materials.


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## rwm

TX COWDOC said:


> I'll check the glass of water / harmonics.  Thanks for all of the info.


This works much better if you use beer. Especially something dark and hoppy...

David- what is the point of the insert holder being tilted and counteracting the angle of the insert? Is this purely for clearance? This tool is labeled as an external threading tool by the manufacturer so clearance would not be an issue? 
Robert


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## pdentrem

I use HSS at home, cheaper and regrind to what I need. Also for threading I only sharpen one side on one of my tools. With the correct 30 degree offset I get a 60 degree cut. Easier to grind!



The other tool which I use in my boring bar for internal threads is ground on 2 sides but you can see in the photo that one is with a long edge while the other is very short. The cutting edge is the long side. This tool is upside down to the way it is mounted in the bar. 


Pierre


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## TX COWDOC

TX COWDOC said:


> I'll check the glass of water / harmonics.  Thanks for all of the info.


I believe I have too much vibration when the lathe is running.


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## TX COWDOC

Z2V said:


> Hey neighbor
> PM me an address and I’ll send you a 60* HSS tool to try


Hey Z2V - I sent you a PM.  I'll try the HSS to rule this in / out.  I just posted some videos with a glass of water sitting atop the Headstock at both 65 and 300 RPM.  I also noted when I had a dial indicator / NOGA sitting up there as well that is had a vibratory buzz.


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## Larry$

29.5 degrees! I wonder how accurate the markings are?


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## davidpbest

rwm said:


> This works much better if you use beer. Especially something dark and hoppy...
> 
> David- what is the point of the insert holder being tilted and counteracting the angle of the insert? Is this purely for clearance? This tool is labeled as an external threading tool by the manufacturer so clearance would not be an issue?
> Robert


This Laydown threading type of insert has no clearance or relief angle - the cutting edge is perpendicular to the bottom of the insert.  This improves the strength of the insert at the pointed end.  To provide the necessary clearance the insert must be held in the toolholder at a negative rake, otherwise it would just rub rather than cut.  External Laydown type toolholder has a 10-degree negative rake, internal have a 15-degree negative rake (to provide more clearance under the insert working inside a bore).  Then to offset a negative rake (which would essentially tear or scrape away material rather than cut into it), the insert has a top surface geometry that reestablishes a positive cutting angle relationship with the part being machined. 

Rather than hijack this thread further, I'll DM you.


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## TX COWDOC

Larry$ said:


> 29.5 degrees! I wonder how accurate the markings are?


I appreciate the spirit of your comment and will tell you that I removed the compound and marked the cross slide with a center punch after marking with a protractor.  It's between 29 and 30.....so as close to 29.5 degrees as it's going to get.  Whatever the issue is here, it's most likely not the angle.


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## mikey

TX COWDOC said:


> I have the impression that the chatter is visible in the turned and faced surfaces in my pictures as well.  ?



Doc, I have no idea why this pattern is occurring but you're right, there seems to be a chatter pattern on the faced work, too. This suggests that there is some harmonic going on, possibly from the motor? In the pic, you are using a negative rake tool that is not ideal for aluminum but, in general, negative rake tools usually finish well. Much depends on getting the work turning at the proper speed but still, there is something that is causing a regular defect. I've seen threads where this sort of thing turned out to be the motor so it was an electrical issue. Might be good to contact PM to see what they say.


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## TX COWDOC

Thanks Mikey. I emailed PM yesterday.  They are usually pretty good with responses so I'm optimistic for a quick diagnosis / resolution.


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## Z2V

TX COWDOC said:


> Hey Z2V - I sent you a PM.  I'll try the HSS to rule this in / out.  I just posted some videos with a glass of water sitting atop the Headstock at both 65 and 300 RPM.  I also noted when I had a dial indicator / NOGA sitting up there as well that is had a vibratory buzz.


I did not receive your PM for some unknown reason.


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## savarin

I used to see that sort of pattern on my aluminium threading.
On my flexi 9x20 it was total lack of rigidity in the compound/topslide system, it could visibly be seen moving in some instances.
With a dial indicator on the top of the tool bit it flexed up and down like a yo-yo (bit of exageration but you get my drift)
I removed the compound and replaced it with a solid plinth, always use very sharp honed HSS and dive in at 90' now for all my threading with no problems.


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## davidpbest

savarin said:


> I removed the compound and replaced it with a solid plinth, always use very sharp honed HSS and dive in at 90' now for all my threading with no problems.


Same here.  Solid tool post mount was the single best improvement I made to my PM1340.  Drastic improvement in parting and plunging in at 90’ when threading.  I haven’t had the compound on the machine for almost two years.


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## savarin

Same here, I only replace the compound for small taper cuts.


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## TX COWDOC

Z2V said:


> I did not receive your PM for some unknown reason.


just sent another. Hope it make it this time. Thanks again -


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## Downunder Bob

In all my years I have never seen single phase induced chatter. Does it only happen in conjunction with carbide inserts. Or is it an excuse for poorly set up machinery.

But yes, if I had chatter I would try HSS. I would also check the mounting of tool post and holder, compound gibs, tool post overhang and compound overhang  all common causes of chatter. I have seen chatter just like that on 3 ph machines.


rwm said:


> This works much better if you use beer. Especially something dark and hoppy...
> 
> David- what is the point of the insert holder being tilted and counteracting the angle of the insert? Is this purely for clearance? This tool is labeled as an external threading tool by the manufacturer so clearance would not be an issue?
> Robert


I always though misadventure was bad planning , and adventure was good planning.


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## TX COWDOC

Downunder Bob,
Best I can tell, everything is tight and not extended. I will try HSS this week.   As you can see in the videos I posted earlier, there is vibration that I cannot localize.  The lathe came with a separate Baldor motor that I swapped out when assembling the lathe.  It is tight and has proper belt tension.  Beyond that I'm not sure what would account for 'poorly set up machinery'.  I am not a trained machinist and appreciate the insights as I sort through this.


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## pdentrem

Drive system
Lumpy belt?
Motor mount is not solidly bolted?
Drive pulley tight to their shaft?
Drive pulley is clean without build up?

Other possible items
Can you lift the carriage either at the front or back?
Compound is sitting on a chip?
Pierre


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## davidpbest

pdentrem said:


> Drive system
> Lumpy belt?
> Motor mount is not solidly bolted?
> Drive pulley tight to their shaft?
> Drive pulley is clean without build up?
> 
> Other possible items
> Can you lift the carriage either at the front or back?
> Compound is sitting on a chip?
> Pierre


These are all good things to check and could be contributing factors.  Put a dial indicator from the cross slide top surface to the top of the threading tool, and observe the readings while cutting threads.   That will give you some indication of the rigidity of your setup. 
Based on your water-glass videos, it does not appear to me to be single-phase motor induced harmonics.   When those issues have come up, the videos make it crystal clear that the motor harmonics are at issue, and I do not see that in your videos.  What I do see is probably belt thrashing or out-of-balance pulleys on the motor or on the headstock end where the belt attaches.  Have you observed the belt-thrashing behavior while threading?  I replaced both pulleys with balanced high-quality version, and the OEM belt with a notched Gates Tri-Power belt on my 1340 and was rewarded with better surface finishes. 







But the kind of surfaces you are getting while threading suggest more severe fluctuations at the cutter-to-part interface.   This could be rigidity issues stemming from the relatively _*weak mounting T-nuts*_ for the compound on this lathe, or it could be some other loose gib in the compound or cross slide, or a loose tool post.  An indicator from the cross slide to the top of the tool doing the cutting will tell a story.


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## TX COWDOC

Here's a video of the pulleys at 65 RPM.  I'll double check the compound  / cross slide tomorrow after work.  I hope to also visit with PM tech support as well.


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## ChrisAttebery

IMHO the SFM is way too slow for carbide. I have an internal threading tool that uses those inserts. It’s been a while since I used it but I think I used 190 or 300 rpm for a 1.935” thread. 

What DOC are you using? Are you taking any spring passes? 

Another thing to try is locking down the compound and use the cross slide for infeed . If that makes a difference then the compound is too loose or flexing. 

You really should try a HSS tool. This is coming from someone who has a rack full of carbide tooling and a 13x40 lathe. 

I have this type of threading/grooving tool holder. I use the HSS threading insert for most of my threading.





__





						Grooving & Cut-Off Tool, 1/2" Indexable HSS Inserts, A R Warner Kit #24 4819
					

Cut-Off Tools 4819 For external grooving and cut-off operations; Includes two 1/16" (.062") groover T-15 high speed steel inserts; Includes two 1/32" ...




					littlemachineshop.com
				








__





						Insert, 60 Degree Threader 4603 - LittleMachineShop.com
					

Indexable Inserts 4603 Cuts 60 degree external threads; Made from T-15 high speed steel; For PN 3572 Grooving & Cutoff Tool; These inserts also fit th...




					littlemachineshop.com
				




Here’s another style that would work for your lathe. 





__





						Threading Tool, External, 3/8" Indexable, HSS Triangle Inserts, A R Warner Kit #17 3695
					

Lathe Threading 3695 For external threading, 8 through 36 TPI; 3/8" shank, 3/8" IC Inserts, 5" long; 2 HSS inserts included: TNMC-32-NV and TPMC-32-NV...




					littlemachineshop.com
				




They also sell sharpened HSS tool bits if you want to try one. 





__





						Tool Bit, 5/16" HSS Threading 2221 - LittleMachineShop.com
					

Lathe Threading 2221 This threading tool bit is sharpened on both ends to a 60° angle for threading.  It is made from high speed steel.  Both ends ar...




					littlemachineshop.com


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## macardoso

I have a 12x36 lathe and have been fighting this issue for 2 years. I get the exact same pattern on most of my threads, regardless of material, size, or part shape/stickout. I have only used carbide, and I have a single phase motor. Swapped belts, strengthened the setup, etc. and nothing has made any difference. 

My thought is slop in the leadscrew. My half nuts are in great condition, but there is endplay in the screw itself due to a lack of thrust bearing at either end. I wonder if cutting forces can push and pull the carriage to slightly advance/retard the position relative to the screw pitch. Once it begins the harmonic forces will tend to continue the pattern on subsequent passes. I have it on my project list to add thrust bearings to the leadscrew.


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## davidpbest

macardoso said:


> I have a 12x36 lathe and have been fighting this issue for 2 years. I get the exact same pattern on most of my threads, regardless of material, size, or part shape/stickout. I have only used carbide, and I have a single phase motor. Swapped belts, strengthened the setup, etc. and nothing has made any difference.
> 
> My thought is slop in the leadscrew. My half nuts are in great condition, but there is endplay in the screw itself due to a lack of thrust bearing at either end. I wonder if cutting forces can push and pull the carriage to slightly advance/retard the position relative to the screw pitch. Once it begins the harmonic forces will tend to continue the pattern on subsequent passes. I have it on my project list to add thrust bearings to the leadscrew.


Before you tear into the leadscrew to add thrust bearings, try snugging up the carriage lock (carriage, not cross slide) a bit so the leadscrew has to labor a bit to advance the carriage.   Kind of a poor-mans preloading of the leadscrew.  That should take out any leadscrew stuttering, and if that does solve the problem then the leadscrew has it's own backlash issues that new thrust bearings and preloading the leadscrew would correct.  Just a thought.


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## macardoso

davidpbest said:


> Before you tear into the leadscrew to add thrust bearings, try snugging up the carriage lock (carriage, not cross slide) a bit so the leadscrew has to labor a bit to advance the carriage.   Kind of a poor-mans preloading of the leadscrew.  That should take out any leadscrew stuttering, and if that does solve the problem then the leadscrew has it's own backlash issues that new thrust bearings and preloading the leadscrew would correct.  Just a thought.


Would you be concerned with added wear to the ways?


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## davidpbest

macardoso said:


> Would you be concerned with added wear to the ways?


I wasn't suggesting this as a permanent fix, just one method to isolate if the leadscrew is stuttering.  Clearly you would not want to continue to run longer term with the carriage dragging - that would create undesirable wear.  But it could help diagnose if the leadscrew is the culprit.


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## Batmanacw

If this was my lathe I'd be checking to make sure my change gears are too tight or running out but I don't think this lathe has change gears.


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## mattthemuppet2

macardoso said:


> My thought is slop in the leadscrew. My half nuts are in great condition, but there is endplay in the screw itself due to a lack of thrust bearing at either end. I wonder if cutting forces can push and pull the carriage to slightly advance/retard the position relative to the screw pitch. Once it begins the harmonic forces will tend to continue the pattern on subsequent passes. I have it on my project list to add thrust bearings to the leadscrew.



I'm not an expert but any end to end play in your leadscrew will show up in cross threading, not chatter. The left hand leadscrew support/ bushing came loose on my Atlas once and trashed a thread. Easy to diagnose, simply close your halfnuts and try and move your carriage back and forth.

The OPs problem looks like bad chatter to me. Something is loose somewhere - spindle bearings, carriage/cross slide/ compound gibs, tool post or tool holder. Vibration from motor or belts is a possibility, especially as plenty of people have described issues with their 12x36/ 13x40 class import lathes on here, but I can't see it producing faceting that bad. I've had mild vibration on my lathe before and it didn't produce this pattern. I did thread a chuck backplate with a whippy home made boring bar and HSS bit that produced *exactly* that pattern though.

I'd start with the list above, beginning with spindle bearing preload, and go from there.


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## macardoso

mattthemuppet2 said:


> I'm not an expert but any end to end play in your leadscrew will show up in cross threading, not chatter. The left hand leadscrew support/ bushing came loose on my Atlas once and trashed a thread. Easy to diagnose, simply close your halfnuts and try and move your carriage back and forth.



What do you do to resolve this if you do identify it as an issue? I see probably 1/8" of movement doing the test you just described. My lathe does not have thrust bearings on the leadscrew.


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## mattthemuppet2

I snugged up the end nut to take up the play, but you could make a simple bronze or steel washer of the right thickness to go between the end of the leadscrew and the right hand support bearing. Hard to say for definite as I don't have any experience of your type of lathe.


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## davidpbest

Any update here?


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## macardoso

I don't want to hijack this thread if my screw issues are not the solution to the faceting issue from the OP, but I bought some hardened steel washers (thrust bearing races) and bearing bronze stock (expensive!). Once my current setup on the lathe gets torn down, I'm going to make a thrust bearing and see if that resolves some of the faceting I see on my threads just like OP.


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## TX COWDOC

davidpbest said:


> Any update here?


Hi Dave - I'll circle back with an update this weekend.


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## 9t8z28

mikey said:


> Wow, better read the reviews on those Accusize tool bits ... maybe better to grind your own?


I agree about these being used only for brass and the like.  They do not hold an edge very well but work great for tools that need to hang out of the tool holder quite a bit.  The only reason I use them is when I need to grind a lot of material off of them for deep internal/external threading where the tool gets long and narrow but again, only for brass.  You can grind a finished tool with these in a few minutes but with HSS from a well known brand you'll be there quite a while with a bench grinder.


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## rock_breaker

It looks like you have filed the top of the threads and wire brushing won't change the cause but it may help the finish.


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## macardoso

In my journey to solve the exact same problem as OP, I purchased a bar of bearing bronze and turned a thrust bearing 0.045" thick, 15mm ID and stock OD. This took up all the slack in the screw with about 1-2 thou left over. I still need to cut some threads to test, but everything feels so much better. The thread lever engages tightly and I don't need to guess if it actually seated correctly in the threads!


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## TX COWDOC

UPDATE:
I'd like to begin with expressing my gratitude to the posters on this thread.  A few members contacted my privately with ideas and suggestions based upon their experiences.
I also wanted to thank Z2V and Bamban for local support with materials and tools.  Granted this is a global forum, these 2 in particular are 'local' since they are less than 2 hours away. 
Also thanks to Darkzero for his My PM1236 thread and MKSJ for his contributions to other similar threads. 
Lastly, thanks to Matt and Mike from Precision Matthews for the calls and offer of support.

Here's all the things I did since last posting.....
I took the motor off and remounted with rubber washers, swapped out the belts to linked belts as suggested by Mark (MKSJ), replaced the compound bolts per Will's PM1236 thread.  Go to use my PM833T for this part.; I also torqued the spindle bearings a tiny bit to address some play I was seeing in my TIR measurements at the chuck. 

There is a substantial improvement in the vibration and noise.  Note the difference in the vibration in the glass of water.

For the work piece (aluminum): I repeated the 16 TPI using the same set up and then again using HSS.  The HSS is best and validates the concerns by many (including Matt) but the Carbide was much improved with the vibration resolved. 

I will chuck up some steel barrel drops courtesy of Bamban and post those.


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## kb58

While I'm glad it's fixed, the frustration for anyone using this as a reference will be left to wonder which of the half dozen factors was the actual problem, unless (worst case) it was a little of everything...


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## Z2V

*Glad to hear that your moving in a positive direction.*


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## jonesn7

Most every comment in this thread was informative. Giving an outcome is a part misding from so many threads, and is much appreciated here. I get so little time to tune my little 7x10 (primarily used to knock out motorcycle spacers or polish MC parts), but I've found some very helpful things throughout the thread.


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## Illinoyance

The speed for manual threading is way below the optimal speed for carbide.  I suggest you try a sharp HSS tool.  Grinding the tool is no big deal.  Use the fish gauge as a template.  Hone to a fine edge after grinding.  Use a stone to create the flat at the tip of the tool.


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## Shootymacshootface

davidpbest said:


> These are all good things to check and could be contributing factors.  Put a dial indicator from the cross slide top surface to the top of the threading tool, and observe the readings while cutting threads.   That will give you some indication of the rigidity of your setup.
> Based on your water-glass videos, it does not appear to me to be single-phase motor induced harmonics.   When those issues have come up, the videos make it crystal clear that the motor harmonics are at issue, and I do not see that in your videos.  What I do see is probably belt thrashing or out-of-balance pulleys on the motor or on the headstock end where the belt attaches.  Have you observed the belt-thrashing behavior while threading?  I replaced both pulleys with balanced high-quality version, and the OEM belt with a notched Gates Tri-Power belt on my 1340 and was rewarded with better surface finishes.
> 
> View attachment 349886
> 
> 
> But the kind of surfaces you are getting while threading suggest more severe fluctuations at the cutter-to-part interface.   This could be rigidity issues stemming from the relatively _*weak mounting T-nuts*_ for the compound on this lathe, or it could be some other loose gib in the compound or cross slide, or a loose tool post.  An indicator from the cross slide to the top of the tool doing the cutting will tell a story.


I am glad that I finally got around to reading this thread. My lathe sat idle for 15 or 20 years before I acquired it. There has always been a rumble and a vibration coming from the Reeves Drive, from a set in the belts I'm sure. I will definitely stop thinking about replacing them, and make it a priority. 
This thread contains a lot of great information!
Good job everyone!


----------



## TX COWDOC

Shootymacshootface said:


> I am glad that I finally got around to reading this thread. My lathe sat idle for 15 or 20 years before I acquired it. There has always been a rumble and a vibration coming from the Reeves Drive, from a set in the belts I'm sure. I will definitely stop thinking about replacing them, and make it a priority.
> This thread contains a lot of great information!
> Good job everyone!


I did not get time to turn / thread any stainless today. The link belts seem to make a nice improvement.  The machine overall is much quieter with the vibration addressed.  As DavidPBest suggested, the glass of water is a quick and dirty way to rule out vibration / harmonics. In this case, I think it was vibration.   It's been a good learning experience sans the time I've lost troubleshooting the issue.


----------



## Shootymacshootface

TX COWDOC said:


> I did not get time to turn / thread any stainless today. The link belts seem to make a nice improvement.  The machine overall is much quieter with the vibration addressed.  As DavidPBest suggested, the glass of water is a quick and dirty way to rule out vibration / harmonics. In this case, I think it was vibration.   It's been a good learning experience sans the time I've lost troubleshooting the issue.


My lathe has definitely been vibrating since day one for me, no need to test. Does anybody know if link belts would work with a Reeves Drive? My guess would be no.


----------



## Bamban

Illinoyance said:


> The speed for manual threading is way below the optimal speed for carbide.  I suggest you try a sharp HSS tool.  Grinding the tool is no big deal.  Use the fish gauge as a template.  Hone to a fine edge after grinding.  Use a stone to create the flat at the tip of the tool.



I am not totally sold about the carbide issue on low speed manual threading. I use carbide laydown on my 90s vintage Jet 1024, and plunge it straight with the cross slide.

This barrel was threaded 3/4x16 to host an adapter to be turned and threaded for a 7/8x32 tuner. I cut the threads using the jog button, and that is slow. The stick out is quite long, the tuner requires 0.9 inch long thread, plus a shoulder.

I have Warner HSS threading bits and carbide special order ones from Thinbit, and a bunch of laydowns from my favorite supplier in China. I could not tell the difference on the thread quality using any of the three types.

The times when I am running 2 lathes I thread in the 1024 using the proximity sensor at higher rpm speeds with the laydown. I am not sure if I could tell the difference in the thread looks.


----------



## davidpbest

Bamban said:


> I am not totally sold about the carbide issue on low speed manual threading. I use carbide laydown on my 90s vintage Jet 1024, and plunge it straight with the cross slide.


I feel exactly the same.  I have had few problems threading with carbide at slow speeds on most materials provided the specific insert is selected with care and knowledge of the cutting geometry, and the setup is rigid (solid tool post advertisement goes here).  Granted I don't thread aluminum often, but I regularly thread 304. 316, brass and bronze with carbide without issue and plunging straight in.  This 29.5° compound technique is very over rated IMO.  The Laydown insert 16ER-AG60-BMC has a great range of suitable materials including aluminum and stainless.


----------



## Aukai

David what holder do you have for that insert?


----------



## davidpbest

I have these:
External:  Carmex* SER0500F16* which is 1/2" shank
External:  Carmex _*075-3EXRHTHL*__ which is 3/4" shank_
Internal:   Dorian   _*881 *_which is a combination internal Laydown and External On-Edge style for BXA QCTP
Internal:   Carmex _*SIR 0625 P16*_ which is a 5/8 x 3/4" shank
They all take the same 16 size inserts, although the internal and external are different inserts.  

The Dorian came with a collection of tools with the QCTP, and unless you want that specific configuration with integrated QCTP mounting block and different external/internal inserts, I would stick with the Carmex.   Hertel, Tool-Flo and Dorian also make square shanked external toolholders similar to the Carmex.  Iscar makes internal shanked toolholders similar to the Carmex internal.


----------



## Janderso

TX COWDOC said:


> https://www.mscdirect.com/product/details/60873023?orderedAs=SER+0625+H16&pxno=13296405&refnum=13296405&rd=k&tg=Recommendations&tpp=false&searchAhead=true&searchAheadTerm=ser%200625&typahddsp=SER%200625%20H16&hdrsrh=true
> 
> 
> 
> 
> 
> 
> https://www.mscdirect.com/product/details/85108983?fromRR=Y
> 
> 
> 
> 
> Here's the tool I'm using.


I didn't know they made negative threading holders/inserts.


----------



## davidpbest

Janderso said:


> I didn't know they made negative threading holders/inserts.


The toolholder mounts the insert at negative rake for clearance.  The insert geometry reverses that to plus 3°.  Discussed/presented _*here*_.


----------



## Aukai

MSC is not recognizing BMC?


----------



## davidpbest

Carmex BMA is the original equivalent.  I have both and the *BMA's* are Carmex, the _*BMC's*_ I have are clones.

Here's the insert from _*MSC*_.


----------



## Aukai

Thank you sir....


----------



## TX COWDOC

UPDATE:
I got the lathe back into position, leveled and tried threading with some barrel drops that Bamban gave me.   Overall, vastly improved.  I tried threading with just the cross-slide and a new AR Warner HSS tool / bit.  16 TPI at 65 RPM.  I fed at 0.003 for 2 passes then 0.002 for 11 passes then 0.001 with a spring pass for 10 passes.  Still feel some coarseness in the threading.  Close inspection of the result reveals some surface irregularity that I can't figure out.


----------



## davidpbest

TX COWDOC said:


> UPDATE:
> I got the lathe back into position, leveled and tried threading with some barrel drops that Bamban gave me.   Overall, vastly improved.  I tried threading with just the cross-slide and a new AR Warner HSS tool / bit.  16 TPI at 65 RPM.  I fed at 0.003 for 2 passes then 0.002 for 11 passes then 0.001 with a spring pass for 10 passes.  Still feel some coarseness in the threading.  Close inspection of the result reveals some surface irregularity that I can't figure out.


Which A.R.Warner insert are you using - TNMC or TPMC?  Looks like tool chatter to me.


----------



## mksj

I would recommend taking deeper cut passes, if the depth is too shallow it wont cut and just push the metal. I take 0.01" per pass on the dross slide, then close to target 0.005" +/- and one spring pass using the cross slide. Multiple passes at the same or close to target depth decrease the finish. on steel. Cutter height and rigidity are also issues. I had better finish and inserts last longer with the lay-down type. Even wit HSS inserts I thing the cutting speeds are low and possibly need better lube. I would start with aluminum and then move to steel and and may need to do some adjustments.

Others have the 1236 and have gotten very good threading finish, but even between the same machine results can vary. Single phase motors are very susceptible to problems depending on the mount isolation and  belt type/tension.


----------



## macardoso

TX COWDOC said:


> UPDATE:
> I got the lathe back into position, leveled and tried threading with some barrel drops that Bamban gave me.   Overall, vastly improved.  I tried threading with just the cross-slide and a new AR Warner HSS tool / bit.  16 TPI at 65 RPM.  I fed at 0.003 for 2 passes then 0.002 for 11 passes then 0.001 with a spring pass for 10 passes.  Still feel some coarseness in the threading.  Close inspection of the result reveals some surface irregularity that I can't figure out.


Bummer, thought you had this all figured out 

Looks way better than the samples you had in the original post. In the last picture above, it almost looks like your spindle side flank of the thread is tearing out while the tailstock flank just has the tiniest bit of chatter. The tearing would be my concern. What material is that? Stainless?


----------



## Bamban

macardoso said:


> Bummer, thought you had this all figured out
> 
> Looks way better than the samples you had in the original post. In the last picture above, it almost looks like your spindle side flank of the thread is tearing out while the tailstock flank just has the tiniest bit of chatter. The tearing would be my concern. What material is that? Stainless?


TXCowdoc may be busy, I will answer for him. The material is a barrel drop 416. I handed him a few to use while he is troubleshooting the problem.


----------



## ChrisAttebery

1. I would work out the process on some 1018 or HRS. Once you get it working on mild steel THEN try the 416 barrel drops.

2. Try using .010" DOC for all but the last pass. Use .005" and then a spring pass. Take more than one spring pass and see if that cleans them up.

3. Are you sure the tool is on center? Drop it down a bit and try again.


----------



## Bamban

ChrisAttebery said:


> 1. I would work out the process on some 1018 or HRS. Once you get it working on mild steel THEN try the 416 barrel drops.


Just curious, why so?


----------



## ChrisAttebery

Bamban said:


> Just curious, why so?



1. Unless he has a bucket full of 416 drops it should be cheaper. 
2. I would think that 1018 should be easier to thread than 416SS.


----------



## davidpbest

416 is gummy and difficult to thread.  Not as difficult as 304 but close.  I too recommend trying to get the threading issues worked out on another material first, then move on to SS.  If you can't thread brass or 1018 without chatter marks, then there is something wrong with the setup (tool height, rigidity of the compound, too shallow of a cut, etc.).  Diagnose this on a more forgiving material before diving into the deep end of the pool (416).   I asked which of the A.R. Warner inserts you are using because a positive rake will work better in SS - it cuts cleaner than a neutral rake, but it does need enough DOC bite to cut instead of just rub intermittantly.


----------



## Bamban

ChrisAttebery said:


> 1. Unless he has a bucket full of 416 drops it should be cheaper.
> 2. I would think that 1018 should be easier to thread than 416SS.


I got a bucket full for him. I just finished doing 28 barrels.


----------



## Liljoebrshooter

416r barrel steel threads very nice.
I  remember going through the same issues when I started.   
Keep trying different things and only change one thing at a time.   I get the best result on my lathe with a Kennemetal NTP2R insert. 
This was after trying about 5 other types.  

Joe


----------



## TX COWDOC

davidpbest said:


> Which A.R.Warner insert are you using - TNMC or TPMC?  Looks like tool chatter to me.


----------



## TX COWDOC

Update 01.19.2021
Fresh TPMC-32 NV HSS tool bit from AR Warner.  

Tool height is correct. It lines up well with the live center in the tailstock and also passes the 6" rule test.

New barrel drop from Bamban.  Confirmed the compound angle to be <30 degrees.

Changed chucks to a 6-jaw (courtesy of Bamban).  Used the live center this time.  Double checked cross and compound gibs.  Locked the compound.  I cannot elicit any movement in the carriage, cross or compound by pushing / pulling.  

Fed from the cross slide: 3 x 0.005; 4 x 0.003; 11 x 0.001 plus spring passes to target depth of 0.0375.  

Same finish.  What I notice most is how rough or course the threading is during the process.  I can hear and feel with my oil brush the courseness in the finish.  I could tell on the 1st 0.005" plunge that the problem was not resolved.  

Also notice the jagged chips.  

How much play should be in the lead screw?


----------



## mattthemuppet2

not sure if this has been mentioned, but what are your turning finishes like? The reason I ask is sometimes insufficient preload can give those results, but that would also show up as a poor turning finish. You can test by mounting a DI or DTI to the head stock to read off the spindle flange, then without a chuck mounted, stick a broom handle in the spindle and pull up with ~50-60lb of force. Deflection on a roller bearing spindle should be <0.0005" (hopefully others with more experience of gear head lathes can chime in).

Personally I agree with the others that say to try a more forgiving material. I started with sch40 pipe, then alu, then steel. I don't think I've threaded stainless, though I have tapped a bunch.


----------



## TX COWDOC

mattthemuppet2 said:


> not sure if this has been mentioned, but what are your turning finishes like? The reason I ask is sometimes insufficient preload can give those results, but that would also show up as a poor turning finish. You can test by mounting a DI or DTI to the head stock to read off the spindle flange, then without a chuck mounted, stick a broom handle in the spindle and pull up with ~50-60lb of force. Deflection on a roller bearing spindle should be <0.0005" (hopefully others with more experience of gear head lathes can chime in).
> 
> Personally I agree with the others that say to try a more forgiving material. I started with sch40 pipe, then alu, then steel. I don't think I've threaded stainless, though I have tapped a bunch.


Turning / facing are fine.  No issues.


----------



## Jim F

Setting tool height with a center or a scale are far from accurate.


----------



## TX COWDOC

Jim F said:


> Setting tool height with a center or a scale are far from accurate.


Thanks for the reply. That was how I was taught during the machining course in Trinidad this summer.  Worked like a champ.  If there is a better way, then please explain.....I'm listening......


----------



## Jim F

Depending on the tool, the cutting edge may not be the point touching the scale.


----------



## savarin

What about cutting a relief wide enough where you want the thread to finish so you can bump up the speed but still have sufficient runout at the end to stop safely
Or cut the thread from the chuck to the tailstock, again so the speed can be bumped right up with no chance of crashing.
Just to see if the finish gets better.
I plunge straight in at 90' on my flexi 9x20 but with a solid plinth instead of a compound and use HSS bits.
The only time I have the problems you show are on crappy hot rolled steel using the compound where I could see the tool bit flexing up and down.


----------



## mattthemuppet2

TX COWDOC said:


> Turning / facing are fine.  No issues.


how about parting?


----------



## TX COWDOC

savarin said:


> What about cutting a relief wide enough where you want the thread to finish so you can bump up the speed but still have sufficient runout at the end to stop safely
> Or cut the thread from the chuck to the tailstock, again so the speed can be bumped right up with no chance of crashing.
> Just to see if the finish gets better.
> I plunge straight in at 90' on my flexi 9x20 but with a solid plinth instead of a compound and use HSS bits.
> The only time I have the problems you show are on crappy hot rolled steel using the compound where I could see the tool bit flexing up and down.


I bought the lathe to build rifles.  I do not intend to have a relief between the lug seat and tenon threads.  I've seen a few videos of machinists (like Joe P.) threading that way.  I built my 1st rifle this summer using carbide at 65 RPM.  Never a problem.  There is an issue here that must be addressed.  Thanks for the feedback.


----------



## TX COWDOC

mattthemuppet2 said:


> how about parting?


Haven't parted anything yet.  Have the blades / holders, etc.  To your initial question, the turning / facing to get a barrel tenon set up have been fine.


----------



## davidpbest

I recommend what savarin suggests. Your swarf tells me the cutting tool is not engaging consistently - probably because you are below the minimum SFM or the DOC is too shallow.  Cut a relief and thread into it at twice the RPM.  Repeat with twice the DOC.   Repeat plunging straight in Instead at 30-degrees.  It could also be rigidity issues like compound flex, QCTP flex, QC tool holder rocking at the dovetail, etc - all of which could be verified with a 0.0005” DTI.  I would start by instrumenting the setup and verify you don‘t have rigidity issues at the cutter. Then start experimenting  with more aggressive F & S.


----------



## TX COWDOC

davidpbest said:


> It could also be rigidity issues like compound flex, QCTP flex, QC tool holder rocking at the dovetail, etc - all of which could be verified with a 0.0005” DTI.  I would start by instrumenting the setup and verify you don‘t have rigidity issues at the cutter. Then start experimenting  with more aggressive F & S.


So place the DTI tip on top of the threading tool and monitor for movement while threading?


----------



## davidpbest

TX COWDOC said:


> I bought the lathe to build rifles.  I do not intend to have a relief between the lug seat and tenon threads.  I've seen a few videos of machinists (like Joe P.) threading that way.  I built my 1st rifle this summer using carbide at 65 RPM.  Never a problem.  There is an issue here that must be addressed.  Thanks for the feedback.


We all understand you ultimately don't want a big thread relief, but you need to experiment first to discover what's going wrong with your setup.  If you're not comfortable threading at 200 RPM without a thread relief area to land in, then cut a thread relief and try it anyway.  This is a process of eliminating all the variables one step at a time.  Like I said before, I would start by putting sensitive indicators on the cutting platforms and seeing what, if anything is jittering around during the cutting opeartions.  I can't imagine getting the kind of swarf you're getting and not being able to see the source of the intermittent cutting with sensitive indicators on your setup.


----------



## TX COWDOC

davidpbest said:


> We all understand you ultimately don't want a big thread relief, but you need to experiment first to discover what's going wrong with your setup.  If you're not comfortable threading at 200 RPM without a thread relief area to land in, then cut a thread relief and try it anyway.  This is a process of eliminating all the variables one step at a time.  Like I said before, I would start by putting sensitive indicators on the cutting platforms and seeing what, if anything is jittering around during the cutting opeartions.  I can't imagine getting the kind of swarf you're getting and not being able to see the source of the intermittent cutting with sensitive indicators on your setup.


Will do tomorrow evening and report back.


----------



## davidpbest

Here are the control surfaces I would instrument with a 0.0001" or 0.0005" indicator (tenths):

Carriage to bedways
Carriage to compound
Carriage to top or side of QCTP
Carriage to top of the A.R. Warner threading toolholder.

Do one at a time and observe the fluctuation in the indicator during the cutting operation.  This should tell you if you have rigidity issues.


----------



## Aukai

Nicely drawn out David


----------



## qualitymachinetools

As Always, David and others have some excellent points to try. Are any of you guys looking for a job? We have some great people here, but definitely are looking for a few more experts to take some weight from my shoulders! (Not kidding, but back to figuring out the problem)

I will post my thinking here, just to keep it all in one place, and so others can use this as a resource in the future. If anyone has more comments or thinks any of my points are not correct, please feel free to chime in, I have been doing this a long time, but I am certainly not perfect, no one is.


*1. This helps with eliminating the single phase motor vibration: *Run the machine at the speed you are cutting, leave the tool engaged in the work, cut the motor power (Put the spindle on/off lever in off). Leave the tool to keep cutting and as it coasts to a stop, see if the pattern goes away right away. If so, its probably vibration from the single phase motor.  You may have to up the speed to get it to coast enough to see if this makes a difference.    Are you having other finish problems though? It would not usually just show up in threading. **I recommend this with HSS tools, less likely to snap as it slows down - Wear Glasses (Always), and not too heavy of a cut.

*2. Speeds and DOC: *What speed are you running at? I have been through this with people before, and the only way I could reproduce this exact type of pattern was going very slow and deep cuts. Reproduced on my known good 1440GT that we turn good parts out on all the time. I would say try around 200 RPM and lighter cuts, see what you end up with just to try it. 

*3. *Are you using the same cutting oil that Bamban is using, I see you have the same material. Same exact cutter, speeds, Depth, etc?* 

4. Eliminate the leadscrew bearings, doubtful, but eliminating every link:*  Try a left hand thread. See if its identical. Ive never had this change in a finish problem,, but just trying to eliminate things. Once I had a person who had a strange lump in a thread once every so often. This was a much larger lathe. Ended up being chips in a thrust bearing in the leadscrew. Every so often I guess the balls would run the chip over and it would move ever so slightly. But he was making mirror finishes in these larger threads on a part, so it was easy to spot. Probably would not have been noticed otherwise. 

*5. Sort of eliminate the compound moving, but this goes with Davids indicator method he suggested above. *Try without using the compound. Put it on 90 degrees (Parallel with the work, the compound will show 0 degrees), backed up so no overhang. Tighten the gib  lock. Thread like this and see if that takes care of it. But this goes along with the indicators David Best suggested to see if anything moves.

*6.* Here is another way to think of it. Your turning finishes are fine from what you said. Threading is the problem. There is no difference in whats holding any of the tools. Its nothing more than the tool moving along the work piece at a different rate and a different shape.  Try putting it in a coarse feed and feeding your threading tool at the same 65 RPM. Does it cut OK then? You cant get thread depth like this, but can get an idea how its cutting.

*7. Was the original problem fixed in steel, but now this is in the 416? *Reading through it looks like it was improved and working fine, but now its a problem again. *So *Is this still happening in aluminum or other materials now? Or only in the 416? If so, can you make a quick video of the chip forming?

*8. The chip curls in the pictures look very deep to me, just a note. *If you are using your DRO to get back to zero, try the dial instead, just to eliminate anything there. That chip seems way deeper than it should me to me. 

9. Try what the others have said about the threading with the relief. No you didnt buy it to do that, but its a bit step in elimination or narrowing things down. 

 I tried to make it easy to follow, if there are any questions about the steps or what I am thinking, feel free to let me know.


----------



## xr650rRider

A thread relief is not always a bad thing on a barrel.  Some actions, that last thread, can actually interfere with the barrel making up tightly.  The only downside is if you set the barrel back later in it's life and might have a gap in the threads but it's more cosmetic than a mechanical problem.

  Not related to your problem, but I read you were building a 6.5 PRC.  I wonder if your planning on using a SAAMI spec reamer?  Seems there is a real problem if you reload.  By the time you fire 2 or 3 rounds, you can't resize brass enough to avoid heavy bolt lift/clickers.  There have been some reamer prints posted that increase the dimension at the 0.200 datum that fix the issue.  Just a heads up.


----------



## TX COWDOC

Left Hand Thread. DTI @ QCTP side.  New HSS bit.  Changed oil to Viper's Venom.  0.002" with the Cross slide.


----------



## TX COWDOC

Left Hand Thread. DTI @ WaysNew HSS bit. 0.002" with the Cross slide.


----------



## TX COWDOC

Surface finish after a few passes on LH threads.  Very rough.  Didn't thread any further.


----------



## TX COWDOC

RH 200 RPM DTI Tool holder & Compound


----------



## TX COWDOC

RH Thread 200 RPM DTI Tool holder. Ranged from 0.0005" to 0.0008"


----------



## savarin

It looks like the metal is tearing out rather than being cut with a sharp tool.
It actually looks like one of those close up micro photos of a lathe tool in action that shows the metal crumbling.
Do both sides of the cut look the same?
Is the tool bit honed to very sharp?
The last video appears to show a downward flex of the tool holder as it starts to cut, that may be the culprit.
If it flexes downwards at the start it must bounce a little although it didnt seem to.
Why does it drop that much just as the cut starts.


----------



## TX COWDOC

davidpbest said:


> Here are the control surfaces I would instrument with a 0.0001" or 0.0005" indicator (tenths):
> 
> Carriage to bedways
> Carriage to compound
> Carriage to top or side of QCTP
> Carriage to top of the A.R. Warner threading toolholder.
> 
> Do one at a time and observe the fluctuation in the indicator during the cutting operation.  This should tell you if you have rigidity issues.
> 
> View attachment 351796


David,
I took the measurements and posted some videos. What amount of movement on the DTI is acceptable?  I did get movement at the tool holder DTI @ 200 RPM as well as the Compound @ 65 RPM.  All cuts were 0.002" with the cross slide from 0.000 to 0.028 then 0.001 + spring passes until 0.0375.


----------



## TX COWDOC

65 RPM DTI @ Compound.  What amount of movement is acceptable?


----------



## xr650rRider

That looks like a lot of material for a .002" cut off the diameter.  You sure your not doing a .020" cut?   Each tick mark on the dial is .002" off the diameter, so you saying your splitting the tick marks for .001" off of diameter and it's still doing it?  That would usually result in barely a sliver.


----------



## TX COWDOC

xr650rRider said:


> That looks like a lot of material for a .002" cut off the diameter.  You sure your not doing a .020" cut?   Each tick mark on the dial is .002" off the diameter, so you saying your splitting the tick marks for .001" off of diameter and it's still doing it?  That would usually result in barely a sliver.


0.002 on the DRO which is 0.004 total removed off diameter........ not taking a 20 thou cut.


----------



## xr650rRider

OK, you showed your dial, so thought you were using it.  I keep my DRO in diameter mode and I usually take .020 for 1st cut, then .010" for a cut or 2, then .005" up until close to final cut and maybe .002" and then spring pass or 2.


----------



## mksj

Looks like quite a bit of movement on the side of the QCTP and on the top of the tool post rest/slide. Is there a small gap between the base of the QCTP and the foot so it clamps down solidly? Is there any rocking motion when it is sitting either on a flat surface or on the tool post slide. Also is the slide locked down and is the gib set correctly? To me that is quite a bit of movement when the cutter engages.


----------



## TX COWDOC

xr650rRider said:


> OK, you showed your dial, so thought you were using it.  I keep my DRO in diameter mode and I usually take .020 for 1st cut, then .010" for a cut or 2, then .005" up until close to final cut and maybe .002" and then spring pass or 2.


The cross dial and the DRO correlate very closely on this machine.  I am, in fact, using both.  I am not taking heavy cuts.  I begin with 0.001 scratch pass, then increments of 0.002 radially until I am at my last 0.010 then I proceed at 0.001 with a spring pass.   Everyone has their preferences to be sure.  I am getting some telling me heavier cuts and others saying I am taking too much.  Some say speed up and others have clearly demonstrated success in the range I was expecting to work in ~ 65RPM.   

All I want is pretty threads!!


----------



## joebaby

High speed steel 10% cobalt tool bit.  Much lighter cuts, esp. in roughing passes. Set compound at 28 degrees, not 29.5  (the purists will be appalled).  Spend a little time making a fixture to grind the tool bit. Good luck


----------



## davidpbest

TX COWDOC said:


> David,
> I took the measurements and posted some videos. What amount of movement on the DTI is acceptable?  I did get movement at the tool holder DTI @ 200 RPM as well as the Compound @ 65 RPM.  All cuts were 0.002" with the cross slide from 0.000 to 0.028 then 0.001 + spring passes until 0.0375.


I've watched all your videos, and I may be overly anal about all this, but I see evidence of some rigidity issues.  Hard to know if these are the source of your treading woes, but I would first try to get all these tuned out as much as possible.   Here is what I observe and what I would do to check/correct things if this were my lathe:

Watching the first video where you are threading away from the chuck at 200 RPM and indicating to the side of the QCTP, there is evidence of jitter indicating tool chatter in the cutting operation and that something in the setup is allowing the QCTP to flex under load.  Makes me wonder if the QCTP is sitting dead flat onto the top surface of the compound.   If the T-nut securing the QCTP to the compound sticks up above the top surface of the compound, the QCTP will rock under load.
The second video from cross slide to bed ways show minor displacement, but it's enough that I question the fit of the cross slide gib. I would remove the cross slide gib, clean the dovetails surface, and stone the gib on all surfaces to remove any burrs.  I would also check to see if the surfaces that mate to the dovetails are flat with some bluing.
In the videos where you are indicating to the cutting tool and the back of the compound, it appears to me that the compound is flexing as the thread-cutting engages.  This looks like too much movement to me.  The indicator to the tool shows the tool deflecting downward about 5/10ths, and the indicator to the back of the compound shows that surface being tetter-tottered upward almost 0.001".   The possible sources of that flex include:
The bottom surface of the compound rotation ring is not flat where it sits on the surface of the cross slide
there is debris between the mating surfaces of the compound and the cross slide
the securing bolts that lock the compound to the cross slider are not tight
the t-nuts in the circular race inside the cross slide are weak or broken or being pulled up for some reason.  Other users have had issues with one of the t-nuts pulling up when the compound is angled just so and the t-nut ends up positioned just below the access hole. This has been discussed_* at this thread.*_
The gibs in the compound are not fitted and adjusted properly.
I would remove the compound from the cross slide, clean up all the interfaces, and search for the source of the compound rocking.

Looking at the resulting thread grooves, I still question whether the cutting tool is on CL with the spindle.  I would check that with a DTI.  
Also, the best estimate I've seen for SFM for annealed 416 is 120.  Published SFM's I've seen range from 110 to 175.  If your part is 1.25" diameter, using SFM of 120, that works out to a spindle speed of 366 RPM using HSS cutting tool.  If the part is 1.5" diameter, using a 100 SFM, that works out to 250 RPM.  I haven't threaded 416, but with 316 and 304 if you go too slow, the material tears rather than cuts and produces the kind of finishes you are seeing.  I'd love to see a thread cut at 350 RPM for comparison.  

Hope this helps.


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## Liljoebrshooter

The 416r barrel steel threads much easier than 304 stainless. 
There are still some issues causing the problems.
Joe


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## Liljoebrshooter

Here is a tennon I  threaded on my 1340 jet.  Same material.   416R from Krieger. 
 I had many of these same issues when I began threading.    David listed many of the problems I had with my machine. 

Joe


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## TX COWDOC

Liljoebrshooter said:


> Here is a tennon I  threaded on my 1340 jet.  Same material.   416R from Krieger.
> I had many of these same issues when I began threading.    David listed many of the problems I had with my machine.
> 
> Joe


Nice work. What is your approach? Speed? Tool type?


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## TX COWDOC

davidpbest said:


> I've watched all your videos, and I may be overly anal about all this, but I see evidence of some rigidity issues.  Hard to know if these are the source of your treading woes, but I would first try to get all these tuned out as much as possible.   Here is what I observe and what I would do to check/correct things if this were my lathe:
> 
> Watching the first video where you are threading away from the chuck at 200 RPM and indicating to the side of the QCTP, there is evidence of jitter indicating tool chatter in the cutting operation and that something in the setup is allowing the QCTP to flex under load.  Makes me wonder if the QCTP is sitting dead flat onto the top surface of the compound.   If the T-nut securing the QCTP to the compound sticks up above the top surface of the compound, the QCTP will rock under load.
> The second video from cross slide to bed ways show minor displacement, but it's enough that I question the fit of the cross slide gib. I would remove the cross slide gib, clean the dovetails surface, and stone the gib on all surfaces to remove any burrs.  I would also check to see if the surfaces that mate to the dovetails are flat with some bluing.
> In the videos where you are indicating to the cutting tool and the back of the compound, it appears to me that the compound is flexing as the thread-cutting engages.  This looks like too much movement to me.  The indicator to the tool shows the tool deflecting downward about 5/10ths, and the indicator to the back of the compound shows that surface being tetter-tottered upward almost 0.001".   The possible sources of that flex include:
> The bottom surface of the compound rotation ring is not flat where it sits on the surface of the cross slide
> there is debris between the mating surfaces of the compound and the cross slide
> the securing bolts that lock the compound to the cross slider are not tight
> the t-nuts in the circular race inside the cross slide are weak or broken or being pulled up for some reason.  Other users have had issues with one of the t-nuts pulling up when the compound is angled just so and the t-nut ends up positioned just below the access hole. This has been discussed_* at this thread.*_
> The gibs in the compound are not fitted and adjusted properly.
> I would remove the compound from the cross slide, clean up all the interfaces, and search for the source of the compound rocking.
> 
> Looking at the resulting thread grooves, I still question whether the cutting tool is on CL with the spindle.  I would check that with a DTI.
> Also, the best estimate I've seen for SFM for annealed 416 is 120.  Published SFM's I've seen range from 110 to 175.  If your part is 1.25" diameter, using SFM of 120, that works out to a spindle speed of 366 RPM using HSS cutting tool.  If the part is 1.5" diameter, using a 100 SFM, that works out to 250 RPM.  I haven't threaded 416, but with 316 and 304 if you go too slow, the material tears rather than cuts and produces the kind of finishes you are seeing.  I'd love to see a thread cut at 350 RPM for comparison.
> 
> Hope this helps.


Very informative post. I will look dig into the suggestions tomorrow.  I will confirm tool height this weekend per the Joe P. video shared by Jim F.  


Jim F said:


> Depending on the tool, the cutting edge may not be the point touching the scale.


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## Jim F

If you are dead set against the reverse threading method Joe Pie does, this maybe an option to consider. Both lessen the forces on the tool.


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## Jim F

This a tool holder that came with my lathe. I is too big to fit a SB9 lantern, but I am thinking of making a dedicated holder for it.
It is 1 1/8 tall and 9/16 wide.


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## davidpbest

TX COWDOC said:


> I will confirm tool height this weekend per the Joe P. video shared by Jim F.


If you want to make a tool-height setting device like the Hardinge version Tom Lipton shows in his video, it's_* a fun project. *_  I use mine often.


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## Liljoebrshooter

TX COWDOC said:


> Nice work. What is your approach? Speed? Tool type?


I use a kennametal NTP2R  insert.   Usually at 110rpm(?).   I also feed with the compound for most of the depth and finish with the cross slide the last. 005" or so to get to proper size. 
I did have to do some work on the bottom of the compound.   It was high around the bolts.

Joe


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## qualitymachinetools

These videos are taken on my 1440GT. This machine is known to turn out good threads. See results in the following messages.


1. The video titled: RH Thread 200 RPM DTI Tool holder. Ranged from 0.0005" to 0.0008"         That cut looks like its supposed to. Cutting, not digging. What did the finish look like after that cut?

2. Something that I noticed, you used the cross slide and said you were taking .002". That is a huge cut for .002". Please see my attached videos showing what I am doing at .002" which would be .004 total, and then .004 which would be .008 total.      

3. When you thread the normal way by putting the cross slide back to Zero each time and only advance the compound, how much are you advancing the compound each time? In this test, even .005 at that RPM was too deep. I had to make quite a few light passes to keep the finish nice.


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## qualitymachinetools

No good here, RPM Slow and cuts way too deep. Not cutting, its digging the material out. Seems like the same type of problem.


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## qualitymachinetools

This one moves with the indicatory on the machine, about the same results.


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## xr650rRider

I know my PM-1340GT came with factory installed DRO but the resolution of the scales was not set correctly and did not match the hand wheel movements, I had to change the cross-slide to .0001 uM.


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## qualitymachinetools

This is a good thread, same machine, material, and cutting tool 

.005 DOC on the compound only. 29.5 degrees. 95 RPM.

 When I got down in to the thread more, I backed off, .0025 per cut. This was 8 TPI, I made it a coarse pitch so its easier to see whats going on.

Ended up with good threads.

Proper chip. I did not use oil, I sprayed on some coolant. Id have better results with cutting oil at the slower speeds.

Notice the chip is smooth like it should be during these cuts. Not tearing like in the other videos.


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## qualitymachinetools

This is while cutting, before any finish work. Just a quick job to get a post here, with oil and finish it could be even better.


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## qualitymachinetools

With oil, .001" on the compound finish pass. 
FYI this material is 1018 CRS. Not the best for finishes, but still turned out OK.


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## TX COWDOC

qualitymachinetools said:


> These videos are taken on my 1440GT. This machine is known to turn out good threads. See results in the following messages.
> 
> 
> 1. The video titled: RH Thread 200 RPM DTI Tool holder. Ranged from 0.0005" to 0.0008"         That cut looks like its supposed to. Cutting, not digging. What did the finish look like after that cut?
> 
> 2. Something that I noticed, you used the cross slide and said you were taking .002". That is a huge cut for .002". Please see my attached videos showing what I am doing at .002" which would be .004 total, and then .004 which would be .008 total.
> 
> 3. When you thread the normal way by putting the cross slide back to Zero each time and only advance the compound, how much are you advancing the compound each time? In this test, even .005 at that RPM was too deep. I had to make quite a few light passes to keep the finish nice.


Hi Matt,
Thanks for posting the videos.  No doubt the 1440GT produces nice threads.  I could post similar 16TPI threads from the Sharps lathe I used this in Trinidad, CO while building my rifle.  The issue is the 1236 has not been producing those kinds of threads.  To clarify the range in line 1. quoted above (0.0005" to 0.0008") was the movement on the DTI not what I was dialing in on the cross-slide. I was taking cuts of 2-3 thousandths at a time.  These are hardly heavy cuts.  Bamban travelled down to my shop today.  We figured it out........


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## rwm

Wait...what...you figured it out???? You have us all on the seats of our collective chairs with this drama!
What is the answer?
Robert

Edit: You forgot to lock the lever on the QCTP?! (ask me how I know)


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## TX COWDOC

Bamban travelled 2 hours south to help me sort through this today! What a guy.  Looked over the machine.  Checked the gibs.  Watched me thread with the same results. New HSS tool.  We disassembled the compound and discovered the compound did not seat squarely on the cross-slide.  See video below.


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## TX COWDOC

We spent 2 hours honing the surfaces of the cross-slide and the compound until the movement was gone.


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## davidpbest

TX COWDOC said:


> Bamban travelled 2 hours south to help me sort through this today! What a guy.  Looked over the machine.  Checked the gibs.  Watched me thread with the same results. New HSS tool.  We disassembled the compound and discovered the compound did not seat squarely on the cross-slide.  See video below.


Yep, that would sure make threading a challenge.  Once that is rectified, my guess is you'll be able to go back to using carbide.


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## Weldingrod1

What will we DO without mystery!!!

Congratulation on your solution!!!

Sent from my SM-G892A using Tapatalk


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## TX COWDOC

65 RPM. Carbide.  Compound feeds as follows: 0.001" scratch; 0.009", 0.008", 0.006" times 2; 0.003" times 2, 0.002", 0.001 with spring passes until finished. beautiful 16tpi threads.  I could tell on the 1st and 2nd pass that the problem was solved.


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## davidpbest




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## rwm

That makes sense. Glad you figured it out. I'm surprised it didn't show up in turning and facing? Why only threading?
Robert


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## TX COWDOC

rwm said:


> That makes sense. Glad you figured it out. I'm surprised it didn't show up in turning and facing? Why only threading?
> Robert


The interesting aspect of the play in the compound was that it was absent when the compound was oriented at 0 and 90 degrees relative to the spindle axis.  When the compound was moved to the correct setting for threading it rocked.  I've got more videos of the DTI moving across these surfaces. Suffice it to say that there was considerable movement with the DTI at the 1-3 o'clock and the 7-9 o'clock areas of the compound seat. 

With the threading issue addressed, I made a practice run on a Rem 700 tenon.  Mated up nicely.   

Thanks to all for the feedback. I learned a lot about the machine during the process.  I lost a lot of time but made some good friends along the way.


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## Aukai

Skol....


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## rwm

Got it. Time for Bourbon?
R


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## Z2V

Great to hear that you found the problem and was able to resolve it. After we talked earlier, I took mine loose and it seems to mate good all the way around. 
Nice looking threads now.


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## Liljoebrshooter

I had this same issue with my compound.  I was starting to have problems with parting. 
This was my beginning into scraping.   You can still see some layout bluing from it.
Joe


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## qualitymachinetools

Great that you guys got it figured out!


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## Jason812

You live in Shiner and aren't partaking in one of these?  Shame on you, 






Now those are some nice looking threads.


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