# Improving single point thread quality?



## LVLAaron (Feb 22, 2022)

New PM1440GT - My first real lathe. My metal working education is 5 years of Abom79 and This Old Tony, and a week long precision rifle course in Gordy Gritters shop.

I am using the following carbide insert https://www.mscdirect.com/product/details/05765631?rItem=05765631 (Recommended by Gordy) and am practicing to thread barrels. I am using (allegedly) 416 stainless bar I got on ebay. 

I am confident that my tool height is correct. 
Cut is flooded with dark cutting oil. 
Speed is slow, 100rpm-ish
Compound @ 29.5

Cuts are shallow, 5 thou max, last cuts 1-2
All passes are done by advancing the compound, except for the last pass, I push the crossslide in a though.

I did lick the top of these threads with a file because they were sharp as a cats claw. 

Because I am new at this I don't know what I don't know and am open to questions, feedback, etc etc. Let me have it.


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## WobblyHand (Feb 22, 2022)

I'll bite.  What thread are you trying to cut?  What TPI?  The inserts show they can cut between 16-48 TPI.  Can you show a picture of your lathe showing the compound?  Not a super close up, but one where one can see the compound and the chuck.  

The close up photos seem to have some distortion due to the lens.  I also have found taking good pictures of threads is hard.  I do see what appears to be a little chatter, if I understand the picture.  416 should cut well.


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## LVLAaron (Feb 22, 2022)

16 TPI - Disregard the part in the chuck - I was working on something else, but this is how I'd have it set for threads.


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## mmcmdl (Feb 22, 2022)

At 100 rpm , what does your surface speed work out to ? 100rpm sounds very slow to me . JMO .


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## MrWhoopee (Feb 22, 2022)

Compound angle is wrong. Should be 30.5 º from parallel to cross-slide (zero mark).

edit: correction, 29.5º


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## mmcmdl (Feb 22, 2022)

Why is your lathe standing on end ?


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## WobblyHand (Feb 22, 2022)

LVLAaron said:


> View attachment 397649
> 
> 
> 16 TPI - Disregard the part in the chuck - I was working on something else, but this is how I'd have it set for threads.


Your compound does not look right.  It appears to be set at 60 degrees, not 30.  Should be closer to the cross slide.  Every new guy gets tripped up on this.  Different manufacturers measure the angle different.  Angle should be 29.5 degrees towards tailstock, with 0 degrees being perpendicular to the spindle axis.


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## Janderso (Feb 22, 2022)

MrWhoopee said:


> Compound angle is wrong. Should be 30.5 º from parallel to cross-slide (zero mark).


Not 29.5?


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## MrWhoopee (Feb 22, 2022)

mmcmdl said:


> Why is your lathe standing on end ?


You've never heard of a vertical lathe?


Janderso said:


> Not 29.5?


Correct, 29.5.


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## Just for fun (Feb 22, 2022)

Watching and learning.


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## LVLAaron (Feb 22, 2022)

Doh! I knew about this and still got tripped up. That's one problem solved.


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## jocat54 (Feb 22, 2022)

Those are some really clear photos, what are you using for camera?


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## LVLAaron (Feb 22, 2022)

jocat54 said:


> Those are some really clear photos, what are you using for camera?


The two close ups are a teslong bore scope with the reflector removed.


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## davidpbest (Feb 22, 2022)

Your RPM's are too low.  Work out the proper SFM.


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## jwmay (Feb 22, 2022)

So its 59.5 on this compound? Why even say 29.5, if the witness mark is nowhere near that indication? I'm not scolding the OP by the way. I'm just trying to blame someone else for my SEVEN YEAR RUN of never successfully cutting threads...


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## LVLAaron (Feb 22, 2022)

jwmay said:


> So its 59.5 on this compound? Why even say 29.5, if the witness mark is nowhere near that indication? I'm not scolding the OP by the way. I'm just trying to blame someone else for my SEVEN YEAR RUN of never successfully cutting threads...



It should be (happy to be wrong) 60.5 with the marks on my machine - this provides relief on the right hand side of the cutter so it doesn't rub. I think it's an "american vs import" lathe thing.


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## WobblyHand (Feb 22, 2022)

Yes, 60.5 degrees on @LVLAaron's machine, and mine.  This is such a common problem, which is why I asked for a photo.  Got me in the beginning as well!  Fixing the angle should help some.


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## LVLAaron (Feb 22, 2022)

davidpbest said:


> Your RPM's are too low.  Work out the proper SFM.



I'll be working up against a shoulder... so naturally I'm nervous about crashing the machine or wrecking a 400 dollar part. I did some testing with the spindle in reverse and using an internal threading insert on the outside of the part. 

Will play around with it tomorrow when the bourbon wears off.


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## WobblyHand (Feb 22, 2022)

jwmay said:


> So its 59.5 on this compound? Why even say 29.5, if the witness mark is nowhere near that indication? I'm not scolding the OP by the way. I'm just trying to blame someone else for my SEVEN YEAR RUN of never successfully cutting threads...


Start your own thread on threading.  We will all try to help you.  It is a good skill to have.


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## MrWhoopee (Feb 22, 2022)

davidpbest said:


> Your RPM's are too low.  Work out the proper SFM.


I was going to point this out, but we all know how intimidating threading is in the beginning, even at low speeds.  HSS would probably a better choice for learning to thread. With the angle corrected, things should be better.


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## MrWhoopee (Feb 22, 2022)

LVLAaron said:


> I'll be working up against a shoulder... so naturally I'm nervous about crashing the machine or wrecking a 400 dollar part. I did some testing with the spindle in reverse and using an internal threading insert on the outside of the part.
> 
> Will play around with it tomorrow when the bourbon wears off.


I would be getting a lot of practice before I tried to thread a $400 part.


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## WobblyHand (Feb 22, 2022)

MrWhoopee said:


> I was going to point this out, but we all know how intimidating threading is in the beginning, even at low speeds.  HSS would probably a better choice for learning to thread. With the angle corrected, things should be better.


First one needs to work out the basic timing for threading - just getting used to it.  After a while, he can speed it up.  It is good to practice on higher TPI at first as well.  4 TPI at normal speeds is terrifying to a beginner!


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## LVLAaron (Feb 22, 2022)

MrWhoopee said:


> I would be getting a lot of practice before I tried to thread a $400 part.



I have a milk crate full of 1.5 inch bar stubs to practice with.


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## LVLAaron (Feb 22, 2022)

MrWhoopee said:


> HSS would probably a better choice for learning to thread. With the angle corrected, things should be better.



Working on choosing and getting a grinder/tool to sharpen HSS and carbide. I know it would be easier, but I can't make the tools at the moment.


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## WobblyHand (Feb 22, 2022)

LVLAaron said:


> I have a milk crate full of 1.5 inch bar stubs to practice with.


After a little bit of practice, add in the shoulders to make it real!


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## ErichKeane (Feb 22, 2022)

jwmay said:


> So its 59.5 on this compound? Why even say 29.5, if the witness mark is nowhere near that indication? I'm not scolding the OP by the way. I'm just trying to blame someone else for my SEVEN YEAR RUN of never successfully cutting threads...


Its kind of silly.  For some reason the Asian manufacturers of machine tools seem to have selected a different 'reference' for a lot of things, in this case, what the 'compound' angle is.  On non-asian machines, "0" degrees is perpendicular to the material, on Asian machines it seems they choose 90 to be perpendicular.  



MrWhoopee said:


> I was going to point this out, but we all know how intimidating threading is in the beginning, even at low speeds.  HSS would probably a better choice for learning to thread. With the angle corrected, things should be better.





LVLAaron said:


> Working on choosing and getting a grinder/tool to sharpen HSS and carbide. I know it would be easier, but I can't make the tools at the moment.



I too would suggest HSS.  What I find interesting, is carbide cuts really well at fast speeds, but does poorly when you get too low.  HSS can't cut as fast, but seems to give a nearly as nice finish from really low RPM up to the max.

You CAN buy HSS insert tooling, which I hear good things about (@davidpbest  can probably give you the best hints as our resident insert guy!), OR you can buy pre-ground HSS tooling that is pretty darn good, and probably just needs dressing every once in a while.


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## WobblyHand (Feb 22, 2022)

Another HSS alternative is an Aloris xXA-8 threading tool.  Uses an HSS blade.  


			https://www.aloris.com/image/cache/catalog/AXA-8-1000x1000.jpg


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## LVLAaron (Feb 22, 2022)

Couldn't go to bed and leave things hanging. After correcting the compound I took some cuts. Same material, same speed - Felt and sounded better, and most importantly, leaves an acceptable finish. No time for a super close up, but will take one in the morning for posterity. 

Thank you everyone!


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## Watchwatch (Feb 22, 2022)

Thread away from the chuck. Makes threading trivial. Checkout YouTube JoePi

Threading tool upside down in the holder; spindle in reverse. You can also leave the half nut engaged and jog the tool back into position.


Sent from my iPhone using Tapatalk


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## LVLAaron (Feb 22, 2022)

I’ve played with it. I mentioned earlier using an internal boring bar and the spindle in reverse. That way the tool forces aren’t lifting the carriage assembly, and I can see the tool. Makes me feel better.


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## davidpbest (Feb 22, 2022)

ErichKeane said:


> You CAN buy HSS insert tooling, which I hear good things about (@davidpbest  can probably give you the best hints as our resident insert guy!), OR you can buy pre-ground HSS tooling that is pretty darn good, and probably just needs dressing every once in a while.


When I need to thread slowly, I use an indexable “On Edge” threading tool (yours is the “Lay Down“ type), and HSS inserts from AR Warner.   Here is a link to one version of that tool, and the HSS inserts that go with it. 









						Kit #18 1/2 inch Threader NV
					





					www.arwarnerco.com


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## LVLAaron (Feb 22, 2022)

davidpbest said:


> When I need to thread slowly, I use an indexable “On Edge” threading tool (yours is the “Lay Down“ type), and HSS inserts from AR Warner.   Here is a link to one version of that tool, and the HSS inserts that go with it.
> 
> 
> 
> ...


Debating that. Saw it in your book!


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## mksj (Feb 22, 2022)

I would practice with what you have rather than running out and replacing your threading tools. You lathe should be rigid enough to just use the cross slide so you do not have any issues with threading angles. I have been using laydown (Carmex A16ER or IR AG60 which has a wider pitch range of 8-48) with good results in a wide range of materials. When using the cross slide I zero the dial when the tip just touches the OD, then advance it 0.01" per pass until close to target, then take the last pass at target and then a spring pass. I use to thread at around 120 RPM in steel, but now thread on upwards of 300+ RPM in steel and 500-600 RPM softer metals since I do not need to worry about the stopping position. On edge HSS may work better at lower SFM's, I previously used on edge TPMC/TNMC used years ago, they were horrible and constantly broke. Switching to the Carmex lay down I am still on the same insert after years of use.

If I am doing a deeper thread pitch then I will be more aggressive on my first passes.

Example of threading passes:


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## mikey (Feb 23, 2022)

Look up "thread relief" and try to incorporate one whenever possible.


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## davidpbest (Feb 23, 2022)

I use the same technique Mark (@mksj) does, but of course I have a proximity stop system like he demonstrates - it really takes the pucker factor out of threading to a shoulder.  If you're nervous about cutting to a shoulder, having a thread relief landing zone is helpful, and will ensure you aren't stopping a carbide cutter "in the groove" which will often fracture the insert.  Also, if you're worried about overshooting and don't have a proximity stop, you can always employ a carriage stop.  And like Mark, I prefer the laydown inserts like you have been using, and I don't advance the cut with the compound angled, but instead drive in perpendicular to the spindle axis on successive cuts using the cross slide.  But there have  been situations with 304 where the OnEdge type with HSS inserts makes a cleaner cut because it has less tendency to work harden the material.  With stainless, once the work hardens, getting a decent thread cut on successive passes is challenging - often the threads tear and leave a nasty finish.


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## Downunder Bob (Feb 23, 2022)

MrWhoopee said:


> You've never heard of a vertical lathe?
> 
> Correct, 29.5.


Takes up less floor space on end.


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## mmcmdl (Feb 23, 2022)

Other than an ELS or a CNC lathe , you could go with a trav-a-dial on a lathe to aid in threading . Easy to watch a dial or indicator vs. a DRO . After years or doing it for awhile , you'll get comfortable and you won't even think about threading into a relief . You'll just do it .   Thread looks alot better now btw .


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## mmcmdl (Feb 23, 2022)

Downunder Bob said:


> Takes up less floor space on end.


Hm..................................I need to try that out !


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## benmychree (Feb 23, 2022)

As I have stated ever so many times, I was taught to set the compound at 30 degrees off the cross feed center line, and when I went to work everyone in the shop (with 7 lathes) set the compound at 30 degrees, all competent journeyman machinists,  Rather than black oil, I use TapMagic, as it promotes free cutting more than black sulphurized oil, and makes observing the threading operation easier, and I agree that 100 RPM may be too slow, carbide does not like slow cutting speeds.  Personally, I would be using HSS; I use the form ground Aloris threading tools.


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## jwmay (Feb 23, 2022)

benmychree said:


> set the compound at 30 degrees off the cross feed center line


As a person who's read that ever so many times, I can verify that it's not as clear as one might imagine..to everyone.  Lol 
OP I think that solved your problem, yeah? Looks good from here!


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## rwm (Feb 23, 2022)

LVLAaron said:


> I’ve played with it. I mentioned earlier using an internal boring bar and the spindle in reverse. That way the tool forces aren’t lifting the carriage assembly, and I can see the tool. Makes me feel better.


I am not following this? Are you talking for internal threads?


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## Ken226 (Feb 23, 2022)

rwm said:


> I am not following this? Are you talking for internal threads?



I believe he's talking about using an internal threading tool, like a boring bar with a threading insert.   Threading the OD of the part on the back side, running the spindle in reverse.    Threading away from the chuck, so that the cutting forces are directed downward.


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## LVLAaron (Feb 23, 2022)

Ken226 said:


> I believe he's talking about using an internal threading tool, like a boring bar with a threading insert.   Threading on the back side, running the spindle in reverse.    Threading away from the chuck, so that the cutting forces are directed downward.



Yep!


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## LVLAaron (Feb 23, 2022)

OK we're cooking with gas. This fits my BAT M action perfectly. RPM's were very low but the carmex insert says it's designed for slow speeds. Saturated in cutting oil it pulled a beautiful and shiny chip.


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## LVLAaron (Feb 23, 2022)

I'm having the time of my life!


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## Illinoyance (Feb 24, 2022)

All the grief about compound angles on the lathe can be resolved by following one rule of thumb:  The compound slideshould be parallel with the trailing flank of the cutter thentap it about 1/2* toward the cross slide.  This works for V threads of any thread angle (60*, 55*, 47,5* orany other included angle) and Acme or trapezoidal threads.  It works for external threads, internal threads, right or left hand threads.


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## Mitch Alsup (Feb 24, 2022)

LVLAaron said:


> I'm having the time of my life!



There is a tiny section of "Houston Warehouse" that mentions cutting a bevel on the chamber end of the barrel and matching bevel inside the action creates better centering of the barrel in the action.


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## LVLAaron (Feb 24, 2022)

Mitch Alsup said:


> There is a tiny section of "Houston Warehouse" that mentions cutting a bevel on the chamber end of the barrel and matching bevel inside the action creates better centering of the barrel in the action.



I did touch the edges lightly. Wasn't too worried about it as these are just paper weights


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## rock_breaker (Feb 24, 2022)

Good looking threads!


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## Henry Komorowski (Feb 25, 2022)

Watchwatch said:


> Thread away from the chuck. Makes threading trivial. Checkout YouTube JoePi
> 
> Threading tool upside down in the holder; spindle in reverse. You can also leave the half nut engaged and jog the tool back into position.
> 
> ...


Very good suggestion provided you do not have a screw on chuck which could UNSCREW if something goes wrong
with very bad consequences.


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## Papa Charlie (Feb 25, 2022)

LVLAaron said:


> I did touch the edges lightly. Wasn't too worried about it as these are just paper weights


You will find that if you taper the edge of the barrel blank before starting the threads you will get a better start on the threads. Driving the bit into a square often can cause issues. Since you are using a BAT M action, at least you won't have to worry about the lug.
Threads are looking really good. 
If you can, get a hold of some old barrels so that you can practice setup and chambering before you put the actual blank in.
Are you going to shoot BR or F-Class?


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## LVLAaron (Feb 25, 2022)

Papa Charlie said:


> You will find that if you taper the edge of the barrel blank before starting the threads you will get a better start on the threads. Driving the bit into a square often can cause issues. Since you are using a BAT M action, at least you won't have to worry about the lug.
> Threads are looking really good.
> If you can, get a hold of some old barrels so that you can practice setup and chambering before you put the actual blank in.
> Are you going to shoot BR or F-Class?



Good info, and thank you. Getting old barrels is not a problem around here  

Raised on BR by my dad and now an F-Class FTR guy. Along with some AR-Tactical in there for fun.


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## ChristianSilver (Feb 25, 2022)

I thread at 70 RPM all the time on titanium and 17-4 ph…


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## Papa Charlie (Feb 25, 2022)

LVLAaron said:


> Good info, and thank you. Getting old barrels is not a problem around here
> 
> Raised on BR by my dad and now an F-Class FTR guy. Along with some AR-Tactical in there for fun.


Very cool, I got into FTR about 4 years ago with a forced rest period due to the world being locked down. Love the sport. My first barrel was made by Benchmark but plan to use Brux for my next barrel and also to chamber my own. I am fortunate in that I have at least 4 National Champions that live and shoot in my area. Great resource for learning. I can say that I am just now starting to refine my shooting and am feeling pretty good about my performance. I actually won my last two matches, no bragging, just a mile stone for me. Sadly I have only shot out to 500 yards. Would love to shoot 1000 to see what I am really capable of or not. But my wife's health doesn't allow my to travel. Maybe some day.
Good luck with your project. Sounds like you are going about it the right way. All the best.
Feel free to reach out anytime you would like to talk.
Patrick


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## rock_breaker (Feb 27, 2022)

@Henry Komorowski, Thanks for the wake up! I need to make an arbor for slitting saws and was going to use my Clausing MK3 with a threaded spindle instead it will have to be done on the enco with a D1-3 spindle which I haven't done much threading. Guess I won't learn any younger.   
Have a good day!
Rock Breaker


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## Parlo (Feb 28, 2022)

Are you using a full form insert? One specifically for the thread you need will give the correct root & crest radii. It looks like you are using an insert that covers a range of threads so it will not have a crest radius on it & the root radius will probably be too sharp.


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