# How to thread stainless



## FTlatheworks (May 11, 2021)

Just got a pm 1236, bought the master turning and boring set. Definitely doesn’t have everything I thought it would. I work in stainless and need to turn threads, I was wondering if anyone can make reasonably priced shank and inserts for stainless thread turning as well as some good cutters for removing lots of material you recommend.


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## macardoso (May 11, 2021)

As you are learning, stainless is a tricky material to work with. Also the specific grade of stainless really makes a difference in your experience (e.g. 316 is MUCH worse to machine than 440).

Sharp tooling is your friend when it comes to stainless. Some general purpose inserts are too blunted (intentionally) to form a nice chip without tearing in SS. Try some HSS, or select material specific inserts for SS. I have even used aluminum specific inserts to machine stainless due to their very sharp edge (the tool life is not great, but was fine for my needs).

A 12x36 should give you enough rigidity to take a healthy cut, but you probably won't be ripping through material like Abom79. I'd start with perhaps a general purpose CCMT insert for roughing, then a CCGT or HSS for finishing. Try HSS for threading too. There are extra sharp carbide threading inserts out there if you know what to look for. Play with the spindle speed and feedrate setting on the gearbox to dial in a cut you can keep the machine running all day. Then adjust your depth of cut as necessary to keep the spindle nicely loaded during roughing. Coolant is recommended. I personally like a squirt bottle full of synthetic coolant (mostly water) used in CNC machining centers rather than oil (no smoke).


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## macardoso (May 11, 2021)

You may also want to practice on a more forgiving material before jumping into stainless (6061 aluminum, 12L14, 41L40, 4140)


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## Janderso (May 11, 2021)

Let us know how you do, what works.
I've never tried to single point stainless.


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## FTlatheworks (May 11, 2021)

I tried hss and it shatters no matter feed/speed, or depth of cut. Unfortunately I can only get 304 here when choosing ss. The parts I make have to be stainless. I have to turn so much material only because I can’t thread yet with the stainless. I have made several parts successfully. I don’t practice on easier material because I know I can do the easier materials, but also I don’t have a use for them. I have trouble grinding hss angles for tools.

isnt the ccgt inserts for brass and aluminum?


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## FTlatheworks (May 11, 2021)

Not shatter, I’m being dramatic. It chips.


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## DAT510 (May 11, 2021)

304 SS is tough one to start with.... It work hardens just looking at it.  If you need to stay in the 300 series SS, 303 is easier to machine with very similar specs as 304.  If you are stuck with 304, my experience is you have to cut deep and fast to cut through and prevent work hardening.  Shallow cuts at slow speeds, ends up more "rubbing" the SS and causing it to work harden and destroy tooling.


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## benmychree (May 11, 2021)

I have cut literally (multiple) hundreds (maybe thousands?) of pounds of stainless in manufacturing products for the wine industry, I used all 303 stainless for the products requiring stainless, I used TPG inserts for all turning and boring in an appropriate grade for non ferrous metals, for threading I used Aloris threading tools in HSS, or Geometric automatic dies with HSS chasers.


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## FTlatheworks (May 11, 2021)

This forum is awesome. I will try to get some 303. I will try all of the above inserts as well. Let you know soon.


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## FTlatheworks (May 11, 2021)

Anyone have a suggestion for a cheaper shank and threading insert that they like for stainless?


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## ttabbal (May 11, 2021)

Remember, which grade of stainless matters. You mentioned 304 and are looking at getting 303. I've done both and didn't do anything real special. On 304 I used import carbide inserts and a holder I got from ebay. On 303 I use HSS that I grind. I can't see HSS chipping on 304 unless you are running way too fast, which you shouldn't be for threading. 

I don't use the compound when threading, just straight in. It might help to use it on 304 due to work hardening though. Use plenty of cutting fluid. I find tap magic works pretty well, kool-mist in the sprayer is nice as it keeps temperature down. If you hone the HSS properly, it should help keep the heat down. 

For general turning I usually use HSS, but if I want to remove a lot of material quickly carbide is nice. As it's for roughing, I don't really worry about the finish and just let it be a bit rough. My carbide holders are all import stuff, but I do have some brand name inserts that work well with them. Well, they claim to be brand... Hard to say sometimes with ebay, but I'm not willing to pay new prices for my hobby.


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## FTlatheworks (May 11, 2021)

I was running 65 rpm. It was 304 and they were hss brazed inserts at 60 degree angles. I went in at 30 degrees. They chipped instantly.


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## FTlatheworks (May 11, 2021)

FTlatheworks said:


> I was running 65 rpm. It was 304 and they were hss brazed inserts at 60 degree angles. I went in at 30 degrees. They chipped instantly.


29 degrees not 30


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## MrWhoopee (May 11, 2021)

Start with something like this:








						9.3US $ 50% OFF|External Thread Turning Tool Holder Ser 1212h16 Ser1616h16 Ser2020k16 Ser2525m16 + 10pcs Carbide Insert Mmt16er Lathe Parts Tool - Turning Tool - AliExpress
					

Smarter Shopping, Better Living!  Aliexpress.com




					www.aliexpress.com
				




Available with 12, 16, 20 and 25 mm shank.


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## mksj (May 11, 2021)

I would go with a lay down type threading insert holder with Carmex (Iscar) carbide insert. This seems to be the least expensive, you can go to the Carmex website and they list different inserts grades, although I find the BMA works on a wide range of materials. David Best is the go to person for turning 304 stainless, he also put together a book on indexable tooling which goes through all this in great detail. General turning I use CCMT/CCGT 32.51, you can get inserts specifically for stainless, but you need to have your speed, feeds and DOC dialed in aggressively so it does not work harden. 304 is probably the least forgiving, 303 and some of the other SS grades turn much easier.


			https://latheinserts.com/5-8-LAYDOWN-THREADING-TOOL-HOLDER-4320000672.htm
		



			https://latheinserts.com/CARMEX-16ER-AG60-GRADE-BMA-4230002320.htm
		





__





						Carmex Precision Tools, LLC. - THREAD TURNING
					





					www.carmexusa.com


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## benmychree (May 11, 2021)

For 303 S/S threading, the HSS tools work fine, just run a little slower than if working with mild steel.  The Aloris threading tools work very well and since they are only sharpened on top and have a long length vertically, they have quite a long life.  I do all my threading using the compound at half the included thread angle.


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## benmychree (May 11, 2021)

FTlatheworks said:


> I was running 65 rpm. It was 304 and they were hss brazed inserts at 60 degree angles. I went in at 30 degrees. They chipped instantly.


I can't say that I have ever heard of brazed HSS inserts ---  There are either inserts or there are brazed tools which are likely to be a carbide blank brazed to a steel shank, these, as commercially made may not have enough clearance ground on the leading edge for threading purposes.


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## benmychree (May 11, 2021)

FTlatheworks said:


> 29 degrees not 30


29 versus 30 degrees is a matter of taste, I was educated to use 30 degrees, worked in a large shop in my apprenticeship and as a journeyman, and nobody used 29 degrees, and subsequently nobody that I had working in my business used 29 deg. either.  It is said that 29 deg. is used to clean up the backside of the thread (the RH flank of the thread)  In my observation, the spring passes perform that task well enough.


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## macardoso (May 11, 2021)

FTlatheworks said:


> isnt the ccgt inserts for brass and aluminum?


Yes, but due to the sharp edge, it works very well for semi-finishing and fine finishing in stainless and steels as well. Downsides are moderate tool life, and chips that won't break. You can get a beautiful finish.


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## FTlatheworks (May 11, 2021)

benmychree said:


> I can't say that I have ever heard of brazed HSS inserts ---  There are either inserts or there are brazed tools which are likely to be a carbide blank brazed to a steel shank, these, as commercially made may not have enough clearance ground on the leading edge for threading purposes.


My mistake, they are steel shank and brazed with a hss 60 degree insert. I don’t think they are of a high quality.


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## FTlatheworks (May 11, 2021)

benmychree said:


> For 303 S/S threading, the HSS tools work fine, just run a little slower than if working with mild steel.  The Aloris threading tools work very well and since they are only sharpened on top and have a long length vertically, they have quite a long life.  I do all my threading using the compound at half the included thread angle.


What about hss blanks I grind? I gave up because I thought it couldn’t be done that route?


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## FTlatheworks (May 11, 2021)

macardoso said:


> Yes, but due to the sharp edge, it works very well for semi-finishing and fine finishing in stainless and steels as well. Downsides are moderate tool life, and chips that won't break. You can get a beautiful finish





macardoso said:


> finishing? Meaning a DOC of <.002, or can it be higher.


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## macardoso (May 11, 2021)

FTlatheworks said:


> Semi finishing? Meaning a DOC of <.002, or can it be higher.


Yeah it can be higher, I just wouldn't do your roughing with these inserts as they will wear faster than the blunt inserts that give a crappy finish. The other benefit is that these inserts have a very small minimum depth of cut so you can actually skim tenths off of a part. You can't do that with general purpose inserts. 

I rough within 10 or 20 thou of finish size and take a few passes with these to hit the dimension accurately and with good finish.


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## FTlatheworks (May 11, 2021)

macardoso said:


> Yeah it can be higher, I just wouldn't do your roughing with these inserts as they will wear faster than the blunt inserts that give a crappy finish. The other benefit is that these inserts have a very small minimum depth of cut so you can actually skim tenths off of a part. You can't do that with general purpose inserts.
> 
> I rough within 10 or 20 thou of finish size and take a few passes with these to hit the dimension accurately and with good finish.


Makes sense. Before I knew these were for non ferrous, or softer metals, I tried to rough with them on mild steel. I liked the stick out they had which is why I was attracted to them. Needless to say, I destroyed them in probably 2 mins.


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## macardoso (May 11, 2021)

FTlatheworks said:


> Makes sense. Before I knew these were for non ferrous, or softer metals, I tried to just roughy with them on mild steel. I liked the stick out they had which is why I was attracted to them. Needless to say, I destroyed them in probably 2 mins.


Yeah with these you need to be gentle. As an example, I ran a prototype product job in 316 stainless with these. Very small depth of cut (maybe 3-5 thou) in many passes (CNC) due to poor workholding conditions. I would get 1-2 hours of cutting per insert corner before the finish would get crappy and I would index.

Granted the CNC can control the feedrate better than I can, but still a data point. At $0.50 per edge from import suppliers, it was pretty economical. 

Here is the finish right off the machine in 4140 from those inserts on my 12x36.


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## projectnut (May 11, 2021)

benmychree said:


> I have cut literally (multiple) hundreds (maybe thousands?) of pounds of stainless in manufacturing products for the wine industry, I used all 303 stainless for the products requiring stainless, I used TPG inserts for all turning and boring in an appropriate grade for non ferrous metals, for threading I used Aloris threading tools in HSS, or Geometric automatic dies with HSS chasers.


I'm as old school as you, maybe even older school.  rather than 303 for the wine industry my experience is with 316 in the food industry.  Almost every operation including turning, facing grooving, and threading was done with user ground HSS blanks.  It was my first experience working in a machine shop (no apprenticing just on the job learning) so I had no idea 316 was more difficult to work with than any other material.

I was taught the "proper" methods to turn, thread, etc., etc. by a couple of old Krauts that worked for the Fuhrer in the Fatherland.  They watched like a hawk and made sure you understood the proper feeds, speeds, and angles, and could grind the tool properly.  If you should be so unfortunate as to make a mistake they could unleash an ungodly rampage in German.  I didn't know exactly what they were saying, but between the attitude and a hand across the back of the head it was obvious they weren't pleased.

It took a while to learn to do exactly as instructed, but when you did finally figure it out it was worth the trouble.  After a while it all seemed second nature.  I still do a lot of 316 with 303 and 304 thrown occasionally.  When I'm working and concentrating I can still feel them breathing down my neck, and offering hints as how to do it "properly".  All in all it was a great learning experience, I'm just sorry I started (34 yrs old) so late in my working career.  I would have loved to have started 15 years sooner so I could have learned more.


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## FTlatheworks (May 11, 2021)

macardoso said:


> Yeah with these you need to be gentle. As an example, I ran a prototype product job in 316 stainless with these. Very small depth of cut (maybe 3-5 thou) in many passes (CNC) due to poor workholding conditions. I would get 1-2 hours of cutting per insert corner before the finish would get crappy and I would index.
> 
> Granted the CNC can control the feedrate better than I can, but still a data point. At $0.50 per edge from import suppliers, it was pretty economical.
> 
> ...


4140 is a tool steel and much easier to machine, right? Can you get comparable in 300 series?


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## macardoso (May 11, 2021)

FTlatheworks said:


> 4140 is a tool steel and much easier to machine, right? Can you get comparable in 300 series?












Balls are 316 stainless. Using my CNC mill as a cnc lathe.


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## davidpbest (May 11, 2021)

mksj said:


> I would go with a lay down type threading insert holder with Carmex (Iscar) carbide insert. This seems to be the least expensive, you can go to the Carmex website and they list different inserts grades, although I find the BMA works on a wide range of materials. David Best is the go to person for turning 304 stainless, he also put together a book on indexable tooling which goes through all this in great detail. General turning I use CCMT/CCGT 32.51, you can get inserts specifically for stainless, but you need to have your speed, feeds and DOC dialed in aggressively so it does not work harden. 304 is probably the least forgiving, 303 and some of the other SS grades turn much easier.
> 
> 
> https://latheinserts.com/5-8-LAYDOWN-THREADING-TOOL-HOLDER-4320000672.htm
> ...


I do a lot of 304 work and use indexable tooling exclusively.  @mksj has made excellent suggestions.  

Single-point threading 304 requires best practices and quality tooling to be successful.  The old-school idea of plunging in at 29-30 degrees using the compound to advance DOC is IMO just that - old school, based on HSS usage, and completely unnecessary.  On 304 specifically, that technique puts all the cutting activity on one side of the V-shaped tool, while the other side of the tool is consistently rubbing and work-hardening the 304.  Far better to plunge into the thread perpendicular to the spindle axis.  Material removal rates are also important with 304, the the tendency is run too slow and take shallow cuts which will also work-harden 304.  If you're serious about wanting to master 304 threading and willing to invest in decent indexable tools, DM me, and I'll share some of my techniques and tool suggestions.


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## mikey (May 11, 2021)

I've cut and single point threaded a LOT of austenitic stainless steel over the years but would still defer to John, Mark and David given their production experience. I did want to add a few things, though.

My sense is that you're a novice hobby machinist. No offense, just trying to get a feel for your level of experience. The reason I raise this is because while stainless is not that difficult to work with (it isn't all that hard), it does require you to know how to cut it and experience counts. Every lathe is different, even lathes of the same model, and every user is different. The feeds and speeds listed in tables and charts are intended for industrial lathes and may or may not apply to YOUR lathe.

You also need to know what you're cutting. 303 has sulfur in it so it machines easier and work hardens less. 304 is much harder to cut without work hardening and this is especially true with carbide inserts; 316 is even worse. Work hardening happens with SS because unlike most materials that eject the heat from a cutting operation in the chip, SS tends to retain the heat in the remaining material AND the tool. Temperatures at the point of cut can get into the red heat range on a heavy roughing cut, especially with carbide tools, so work hardening is a real thing. If you can, use 303.

*The keys to turning SS is to use a sharp tool, coolant and you must keep the tool cutting* - do not dwell or the tool will rub and build heat and you'll work harden in an instant in 304/316; feeds matter, especially with SS. The aforementioned CCMT and CCGT inserts will work and David will set you straight on inserts but I would reinforce that you need a positive rake insert on a small lathe when working SS. With that said, I much prefer a good HSS-cobalt tool for stainless steel because I can get it sharper than any carbide insert and I can grind it to reduce cutting forces so that the tool cuts easier without building a lot of heat. While I normally would turn SS on my Emco lathe, I have cut a lot of 303 and 304 on a little Sherline lathe with HSS tools so I know that these tools work. Cobalt will also hold an edge at high temps so the tools stay sharp longer, even with heavy cuts. The problem is that you have to know how to grind these tools.

Coolant matters, especially when using inserts. For me anyway, coolant is used to reduce temperatures at the point of cut as well as for providing lubricity so use some kind of cutting oil or coolant. Sulfur-bearing oils with EP additives work well, as does the water-based AnchorLube. A coolant stream is ideal but dripping coolant or cutting oil at the point of cut works well enough. Regardless of which way you go, use a LOT to try and keep temps down.

For threading, I own the aforementioned Carmex inserts and they work, especially for smaller threads where the helix angle is less of an issue. However, I actually prefer to use a good HSS-cobalt threading tool with 15 degree relief angles for SS because it cuts cleaner at lower speeds so I don't have to deal with work hardening a thread. I cut straight in with my Sherline and set the compound at 29.5 degrees on my Emco lathe and both methods work well.

Another tooling option would be to consider the threading tools from AR Warner; they sell both stand up and lay down style inserts that are sharp T-15 HSS inserts and should work well in SS. Their HSS CCMW turning inserts and SCLCR tool holders are also an alternative to carbide turning tools; they are sharp when new and are easily sharpened by flattening their tops on a fine or extra-fine diamond stone so you might look into them.

Whichever tooling system you choose, practice. These tools don't just magically make you capable just by owning them. You need to learn which speeds, feeds and depths of cut work on the machine you have and the only way to learn this is to cut.


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## Nogoingback (May 11, 2021)

Some folks have suggested  other types of stainless.  I've been making parts from 416 stainless recently and
I find it machines very nicely with a good surface finish I have no experience threading it.  Without knowing your application
I can't say if it's suitable, but it's worth considering.


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## deakin (May 11, 2021)

i thread occasionally in ss usually 304 or 316  didn't know it was a problem. i'm using flood coolant maybe that is why?


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## savarin (May 11, 2021)

I do a lot of threading and turning of stainless but cannot remember what grade other than when I purchase I go for the cheapest of the two grades the supplier carries.
I use only HSS tools honed sharp and never found a problem.


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## FTlatheworks (May 11, 2021)

Maybe it is me then? My problem is the threads are not clean. They end up looking like I’m cutting in different places. They have sharp burs hanging off. It just seams to tear not cut. It was a 5/8 tool blank with 8% cobalt ground to a 60 deg angle.


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## FTlatheworks (May 11, 2021)

mikey said:


> I've cut and single point threaded a LOT of austenitic stainless steel over the years but would still defer to John, Mark and David given their production experience. I did want to add a few things, though.
> 
> My sense is that you're a novice hobby machinist. No offense, just trying to get a feel for your level of experience. The reason I raise this is because while stainless is not that difficult to work with (it isn't all that hard), it does require you to know how to cut it and experience counts. Every lathe is different, even lathes of the same model, and every user is different. The feeds and speeds listed in tables and charts are intended for industrial lathes and may or may not apply to YOUR lathe.
> 
> ...


Thanks, no offense taken. I am a novice, but is there any way you could show me how a picture of a threading tool you have ground. I bought 5/8 blanks and I was kicking myself after because they are awfully big. I feel it would be easier and less wasteful working with something smaller.

 I have always used the compound to increase DOC BY .002 max. I engage the half nut at the appropriate spot based on the thread gauge (don’t know the technical name), and I shut the motor off and reverse, so that I don’t engage the half nut in the wrong place. I run as slow as possible 65 rpms. I couldn’t imagine running faster, but I will try tomorrow. Is there anything about how I’m doing that wrong? It works for softer metals.


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## savarin (May 11, 2021)

All my threading is done at 90' because I have a solid plinth in place of the top slide.
Just to check,  the tool bit point is exactly horizontal?
There is some relief on the two sides and under the point, have you honed a slight radius on the tip?
Can you post a pic of the tool bit


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## FTlatheworks (May 12, 2021)

savarin said:


> All my threading is done at 90' because I have a solid plinth in place of the top slide.
> Just to check,  the tool bit point is exactly horizontal?
> There is some relief on the two sides and under the point, have you honed a slight radius on the tip?
> Can you post a pic of the tool bit


I will post tomorrow. It has an attempt at 7 degree relief.


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## mikey (May 12, 2021)

FTlatheworks said:


> Thanks, no offense taken. I am a novice, but is there any way you could show me how a picture of a threading tool you have ground. I bought 5/8 blanks and I was kicking myself after because they are awfully big. I feel it would be easier and less wasteful working with something smaller.



Sure, go to post 136 to see my threading tools and post 104 for instructions on grinding them.

If I were you, I would use 3/8" HSS-cobalt blanks for threading stainless. Anything larger takes too much effort to grind and costs more.


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## mikey (May 12, 2021)

FTlatheworks said:


> I have always used the compound to increase DOC BY .002 max. I engage the half nut at the appropriate spot based on the thread gauge (don’t know the technical name), and I shut the motor off and reverse, so that I don’t engage the half nut in the wrong place. I run as slow as possible 65 rpms. I couldn’t imagine running faster, but I will try tomorrow. Is there anything about how I’m doing that wrong? It works for softer metals.



A lot depends on the thread pitch you're cutting, the tool you're using and your familiarity with the thread cutting process. It isn't difficult and will get easier with practice.

I will defer to David Best with regard to carbide tooling. In general, however, the smaller the thread, the fewer the number passes required to cut them. There are charts available from the manufacturer of your insert that gives you guidelines on depth of cut per pass, the number of passes required and so on. 

With HSS, the relief angles under the cutting edge actually matters, as does your method of infeed. If you cut straight in instead of using the compound then both flanks are engaged simultaneously and the potential for rubbing is increased unless your relief angles provide clearance for the helix angle of the thread you're cutting. For smaller threads under about 16 tpi, I have found that 15 degrees of side relief is more than enough to avoid excessive rubbing due to the helix angle of the thread but there is still usually some burring. In contrast, when feeding in with the compound only the leading flank is doing most of the cutting and the following flank is doing a clean up. I find that with this type of tooling and my usual 15 degrees of relief, there is almost no rubbing and the threads are much cleaner. This is one reason why I prefer a HSS tool; I get to control the relief angles. To be fair, no way would I rely on HSS in a production situation; I would be using a Carmex BLU insert for that. 

As for technique, each of us has our own way of doing things. When using a HSS tool, I normally start with a scratch pass with a 0.001" depth of cut to make sure my gearing is right for the thread I'm trying to cut. If the pattern is correct then I'll make a 0.009" depth of cut and make a full pass. For my next pass, I cut the depth of cut to 0.005" deep and see how the tool is cutting. If the pass is clean and without burrs then I'll usually take one or two more passes at 0.005", then I usually step down the depth of cut until I am at 0.001-0.002" per pass. The reason for this is because as you go deeper, the amount of cutting edge greatly increases; to keep heat and cutting forces under control you have to reduce your depth of cut or you'll start tearing the material or work harden it. 

Look up how to estimate your total depth of cut and how to use the thread dial indicator. I have to run out soon so I'll leave it to you or others to take it from here.


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## FTlatheworks (May 12, 2021)

mikey said:


> Sure, go to post 136 to see my threading tools and post 104 for instructions on grinding them.
> 
> If I were you, I would use 3/8" HSS-cobalt blanks for threading stainless. Anything larger takes too much effort to grind and costs more.


How do you grind your tools accurately like that. I don’t have the money to buy a nice bench grinder with a table and wider wheels. It’s got a flimsy tool rest. I know it can be done by hand, but I need to get the 3/8 size. 5/8 is difficult to grind equally because the circular shape of the wheel takes more out of the center of the 5/8 tool. When trying to compensate there are unequal high and low spots.


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## FTlatheworks (May 12, 2021)

mikey said:


> A lot depends on the thread pitch you're cutting, the tool you're using and your familiarity with the thread cutting process. It isn't difficult and will get easier with practice.
> 
> I will defer to David Best with regard to carbide tooling. In general, however, the smaller the thread, the fewer the number passes required to cut them. There are charts available from the manufacturer of your insert that gives you guidelines on depth of cut per pass, the number of passes required and so on.
> 
> ...


Thanks, Mikey, it’s much appreciated. People don’t help out too often anymore. This is the most helpful bunch I have had the pleasure of communicating with.


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## mikey (May 12, 2021)

FTlatheworks said:


> How do you grind your tools accurately like that.



Easy. I use a good belt sander and I've paid my dues by grinding a LOT of lathe tools. It isn't hard to do but it does take some practice. Some guys just prefer not to grind tools and that's fine. Luckily, there are HSS and carbide inserts available that will get you up and running quickly. Again, David Best has just published a book on inserted tooling and I encourage you to have a look at it or at least communicate with him.


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## mikey (May 12, 2021)

FTlatheworks said:


> Thanks, Mikey, it’s much appreciated. People don’t help out too often anymore. This is the most helpful bunch I have had the pleasure of communicating with.


You're welcome, Sir.

HM is special, and the staff and members work hard to make it so. If you have questions, ask and someone will step up. We have a LOT of knowledgeable members and a number of pros, too, so someone will know the answer. To get the most from the forum, ask questions and interact with the members and I guarantee that you will grow faster and enjoy the forum more. 

What I find especially nice is that we get to watch our members grow from newbies and novices into experienced, confident hobby machinists. Many of the respondents to your questions will be those guys who were in your shoes not that long ago. It is very, very cool to see!


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## FTlatheworks (May 12, 2021)

mikey said:


> You're welcome, Sir.
> 
> HM is special, and the staff and members work hard to make it so. If you have questions, ask and someone will step up. We have a LOT of knowledgeable members and a number of pros, too, so someone will know the answer. To get the most from the forum, ask questions and interact with the members and I guarantee that you will grow faster and enjoy the forum more.
> 
> What I find especially nice is that we get to watch our members grow from newbies and novices into experienced, confident hobby machinists. Many of the respondents to your questions will be those guys who were in your shoes not that long ago. It is very, very cool to see!


I’m talking to both of you. He coincidentally completed I project I only dreamed of doing with my machine. He has given me the confidence to go ahead and attempt it with my lathe.


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## FTlatheworks (May 12, 2021)

Alright, I’m taking a bit of everyone’s advice. I bought 3/8 hss blanks. 1”, 3/4”, 1/2” aluminum stock and an assortment of nuts to test my threads. I will grind my threading tool and post pics of the results of my first attempt and the tool used on the aluminum. Adjust my methods as necessary once we find out if it is me, or the stainless causing problems.


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## DAT510 (May 12, 2021)

You could also think about getting or making tool bit a grinding Gage.  I find it useful in making sure my cutter tip is "Square" and the angles I've ground are correct.  The sides are helpful in setting your clearance angles. 

Back in school I made this one. 




Little Machine Shop sells this one.  https://littlemachineshop.com/products/product_view.php?ProductID=4115


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## FTlatheworks (May 12, 2021)

DAT510 said:


> You could also think about getting or making tool bit a grinding Gage.  I find it useful in making sure my cutter tip is "Square" and the angles I've ground are correct.  The sides are helpful in setting your clearance angles.
> 
> Back in school I made this one.
> 
> ...


I have a starret tool gauge.


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## FTlatheworks (May 12, 2021)

To all following this thread, I believe you were correct about the 5/8 blank being too big. I can see where the tool got too hot under the point. Not enough relief and too much material to remove to begin with.


----------



## FTlatheworks (May 12, 2021)

How’s this boys?


----------



## FTlatheworks (May 12, 2021)

Also this is shorter and smaller than my tool post accepts. Is it safe to only have it secured by two lock down screws to make the tool longer, or do I need to buy longer ones, or shim them. I’m gonna try it now.


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## savarin (May 12, 2021)

Mine are held in by two bolts only and never caused a problem.
I dont know if its the photo but in the first and third ones It looks as if there is a tiny vertical strip along the top edge,  like to get the side relief all the way to the top of the bit.
caveat - I have no formal training the above is what I have found works.


----------



## mikey (May 12, 2021)

FTlatheworks said:


> How’s this boys?



Not quite. There is a gap on the right side and there should be NO gap there. The grind is off angle a bit but that is minor; you just need to align the 60 deg angle so it is dead on perpendicular to the work piece and you use your fishtail for that. 

Be sure to hone the two sides and the top and put a small flat at the tip or the tip will crack off; trust me on that. 

Two hold down screws will work fine in your tool holder.


----------



## FTlatheworks (May 12, 2021)

mikey said:


> Not quite. There is a gap on the right side and there should be NO gap there. The grind is off angle a bit but that is minor; you just need to align the 60 deg angle so it is dead on perpendicular to the work piece and you use your fishtail for that.
> 
> Be sure to hone the two sides and the top and put a small flat at the tip or the tip will crack off; trust me on that.
> 
> Two hold down screws will work fine in your tool holder.


Yes, the grind isn’t perfect by any means. I have to do it completely free hand. I use the grinder at work. The gap is from me holding my phone and trying to hold the gauge at the same time and being crooked On the tool. It fits snug except my flat spot on the nose of the tool. Should my tool for that rectangle in the end of the gauge perfectly? That’s tough freehand!


----------



## FTlatheworks (May 12, 2021)

There’s my aluminum threads. My major and min diameter came out perfect. Finish was ok, but no burrs.


----------



## FTlatheworks (May 12, 2021)

So, need to hone my tool making skills and try SS. Next. After getting the angle perfect and cleaning it up as Mikey suggested.

 Nvm, I see the uneven angle on it Mikey. I can see it in the picture.


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## FTlatheworks (May 13, 2021)

savarin said:


> Mine are held in by two bolts only and never caused a problem.
> I dont know if its the photo but in the first and third ones It looks as if there is a tiny vertical strip along the top edge,  like to get the side relief all the way to the top of the bit.
> caveat - I have no formal training the above is what I have found works.


I’ll take it any help I can get.


----------



## mikey (May 13, 2021)

FTlatheworks said:


> So, need to hone my tool making skills and try SS. Next. After getting the angle perfect and cleaning it up as Mikey suggested.
> 
> Nvm, I see the uneven angle on it Mikey. I can see it in the picture.



Keep in mind that any imperfection of that 60 deg angle will transfer to your thread form so try to get the angles perfect. It just take some time to get it down so stick with it, it will come. Make sure to hone both sides and the top so no grind marks show on your cutting edges, then make that flat.


----------



## savarin (May 13, 2021)

I use those cheap little plastic backed diamond hones, I find they work rather well.


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## FTlatheworks (May 13, 2021)

savarin said:


> I use those cheap little plastic backed diamond hones, I find they work rather well.


I’m unfamiliar with those, except for the ones in the knife sharpening kits. We have a bevel/table/disc grinder, but I ruin a lot of material way faster with that. It’s basically a large motor attached to a piece of sand paper cut in a circle.


----------



## JimDawson (May 13, 2021)

I'm a little late to the party here, but I'll throw in my 2 cents anyway.  I thread 100's of 304 and 303 parts every month (1/2-20), both internal and external.

Internal is all done with a spiral flute, powered metal Guhring machine tap, designed for SS, and using a 50% thread depth drill.




External threading is done with an Accusize insert holder.  https://accusizetools.com/products/...threading-inserts?_pos=3&_sid=9c18780a2&_ss=r

500 RPM, 5 passes with a finish spring pass.  I use a reduced step down strategy where each pass has less depth than the previous and starts at about 0.01 DOC and finishes at about 0.002 DOC.  Flood coolant.









I use these Mitsubishi MMT16IRAG60 VP10MF inserts, designed for SS




I get a little tearout on the 303 SS, but the 304 SS threads are nice and smooth.  I could work with the cutting parameters to clean up the 303 threads a bit, but they meet our needs as they are.

The 304 is much harder on the tools than is 303.  I can get a few hundred parts per edge in the 303, where the 304 I get a couple hundred at best.

Also I just received my new Shars threading insert holder today.  https://www.shars.com/3-4-mtvo-external-threading-grooving-tool-holder-right-hand



and these inserts  https://www.shars.com/tnmc-32nv-tin-carbide-insert

I bought this because we are changing the design of the parts and need the extra clearance. on the face.


----------



## FTlatheworks (May 13, 2021)

JimDawson said:


> I'm a little late to the party here, but I'll throw in my 2 cents anyway.  I thread 100's of 304 and 303 parts every month (1/2-20), both internal and external.
> 
> Internal is all done with a spiral flute, powered metal Guhring machine tap, designed for SS, and using a 50% thread depth drill.
> 
> ...


Very interesting technique. The reduced depth of cut is for cleanup of tearing?


----------



## JimDawson (May 13, 2021)

FTlatheworks said:


> Very interesting technique. The reduced depth of cut is for cleanup of tearing?


Not really to relieve tearout, but more to keep the load on the tool more even throughout the process.  When threading, as you cut subsequent passes the chip gets wider because the tool is cutting on the side of the thread.  So reducing the cut depth reduces the load on the tool.  I used to actually break tools before I started doing it this way.  The finish spring pass at 0 stepover is really the cleanup to try reduce the tearout.  I could most likely eliminate the tearout by adding a couple more stepovers, thus reducing the depth of cut a bit more for each pass, I'm really cutting kind of aggressively.


----------



## ttabbal (May 13, 2021)

FTlatheworks said:


> Very interesting technique. The reduced depth of cut is for cleanup of tearing?



Keep in mind that threading is a form tool. So as you go deeper, you are cutting along the sides as well. You can start out with a deeper DOC, but once you get in a little more, the pressure on the tool increases fast. You control that by taking a shallower cut the further in you go. 

For tearing, you can do the last couple of passes really shallow and a spring pass or two at the end will help clean up the cut. If you want them really clean I guess you could use a thread file to do the last thou or two.


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## FTlatheworks (May 13, 2021)

I cleaned up my cutting tool on a table top disc grinder. I attempted to cut threads (1/2-20). I made 6 thou cuts and it was going great until I got to about 18 thou in. I believe it work hardened, but I’m not sure. I was so close to have a perfect set of threads which is exciting for me.

it sounds like I should have backed off after taking two cuts of 5-6 thou and only taken cut 1-2 from there on? Also, I bumped up my rpm from 65-100. That seems to be fast, but that’s the closest I have ever been to having nice stainless threads. I went in at a 28 degree angle, and I used rapid tap, or magic tap.

Any suggestions?


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## FTlatheworks (May 15, 2021)

ttabbal said:


> Keep in mind that threading is a form tool. So as you go deeper, you are cutting along the sides as well. You can start out with a deeper DOC, but once you get in a little more, the pressure on the tool increases fast. You control that by taking a shallower cut the further in you go.
> 
> For tearing, you can do the last couple of passes really shallow and a spring pass or two at the end will help clean up the cut. If you want them really clean I guess you could use a thread file to do the last thou or two.


What is a spring pass? Here’s my successful thread. I can put the nut on by hand, but it doesn’t look pretty.


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## NC Rick (May 15, 2021)

That’s awesome!  I tried a 5/16-18 thread on 304 today using a die.  I canceled the project do to not needing it badly enough.  While it was working, i would have been there a long time to produce 6 Of ‘em.  Nice work!


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## FTlatheworks (May 15, 2021)

NC Rick said:


> That’s awesome!  I tried a 5/16-18 thread on 304 today using a die.  I canceled the project do to not needing it badly enough.  While it was working, i would have been there a long time to produce 6 Of ‘em.  Nice work!


Ya it took a long time. I used a hss 3/8 blank. Now I know if I invest in fact tooling it will only get better. I calculate the sfm and came up with about 500 rpm. Can anyone confirm that’s correct?

on your project, do you have a tailstock die holder? I hear that’s a guaranteed way to do it.


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## mikey (May 15, 2021)

Your compound angle is off. Asian lathes don't have consistent markings. If your index says 29.5, try setting it to 61.5 and try again.


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## JimDawson (May 15, 2021)

Great start.    You are almost there.

It kind of looks like your thread is not formed correctly and maybe are cutting too much on the back side..  The top of the threads seem to be folded over away from the chuck. The bottom of the threads look to be well formed.  It's hard to tell but the front and back side angle does not look symmetrical.  Also looks like it is cut too deep.  What might help you is to take a few passes with a file before you take the final couple of threading passes, that should eliminate the folded over sharp tops and give you a more visually pleasing thread form.  It almost looks like your cutting edge is not exactly perpendicular to the work.

A 28 degree approach is maybe a little much, 29 or 30 degrees might be better.  With a properly ground 60 degree tool, you can plunge straight in with the approach perpendicular to the work, but this does not always work well.  If you swing your compound around to parallel to the work and step over 1 or 2 thou on each pass then feed in with the cross slide it works well also.   A spring pass is a final pass without going deeper on the compound.  It just cleans up the fuzz on the threads. 

On a 1/2-20 thread, I turn the major diameter to 0.495 and thread to the proper minor diameter.  This gives a better thread form with a bit of a flat on the thread peaks. 

Here is an example of a 1/2-20 thread in 303 SS I did a few days ago.  I'm not sure exactly where the ''chatter'' marks are coming from, but it may actually be chatter that I can't hear.  Or it could be just the way the chip forms on 303 SS.  304 SS seems to be smoother on the thread faces, but we switched to 303 to save on tooling costs.


----------



## JimDawson (May 15, 2021)

FTlatheworks said:


> Ya it took a long time. I used a hss 3/8 blank. Now I know if I invest in fact tooling it will only get better. I calculate the sfm and came up with about 500 rpm. Can anyone confirm that’s correct?



500 RPM is what I use.  Turning the tool upside down, running the spindle in reverse thus feeding away from the chuck will save your nerves when threading at higher RPMs.  Also turning a relief near the shoulder will be very helpful.


----------



## FTlatheworks (May 15, 2021)

mikey said:


> Your compound angle is off. Asian lathes don't have consistent markings. If your index says 29.5, try setting it to 61.5 and try again.


I did it at zero this time.


----------



## FTlatheworks (May 15, 2021)

FTlatheworks said:


> I did it at zero this time.


I’ll try that next. I chased it with a die and it helped, but I don’t have the money for a whole die set to chase every thread I try to cut. 


JimDawson said:


> 500 RPM is what I use.  Turning the tool upside down, running the spindle in reverse thus feeding away from the chuck will save your nerves when threading at higher RPMs.  Also turning a relief near the shoulder will be very helpful.


Your part looks good. Nice job!


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## FTlatheworks (May 15, 2021)

FTlatheworks said:


> I did it at zero this time.


What makes you say that Mikey? Cause of a previous post? Or because you can tell by looking at the threads that I wasn’t setup properly?


----------



## brino (May 15, 2021)

@FTlatheworks

What I see is uneven steps to your threads.
Ideally the angle on the left side is the same as the angle on the right side.

Here's a zoom of what you posted:



The angle to the left of the thread crest look good, but the angle to the right of the thread looks almost square to the bolt axis.
It looks like the thread I exaggerated in sketch in red in that picture.
We want something more like the green one.

When the compound angle is off your threads can look like that.
The problem is that some lathes call zero degrees as the compound travel being perpendicular to the axis of the work (same as the cross feed).
Other lathes call the compound zero degree setting as being parallel to the axis of the work (same as the longitudinal feed).

So what is 30 degrees on one lathe will be 60 degrees on the other lathe!

It is difficult to tell for sure if that's the problem you're seeing.
Usually when that is the problem, the left flank of the thread has multiple little steps in it and yours is one clean face.

It might just be the top of your threads are rolled over so much that it obscures the right flank.

Hopefully that makes sense.
Stick with us, we will help you get this sorted out!

-brino


----------



## mikey (May 15, 2021)

FTlatheworks said:


> What makes you say that Mikey? Cause of a previous post? Or because you can tell by looking at the threads that I wasn’t setup properly?



As Brino is pointing out, your thread form is distorted. If you look at the threads, your tool is cutting on the right side of the tool and leaving a torn edge on the left side of the thread. This suggests that the tool is not oriented properly. If, as you say, the compound was at zero and you fed straight in, then the tool itself is oriented to the right so that it is cutting on the right flank of the tool.

It is critical that the tool be ground properly with an accurate 60 degree included angle at the tip. The center of this 60 degree angle MUST be perpendicular to the work piece. The tip of the tool must also be on the spindle center height.

With the tool oriented correctly as above, if you feed straight in then both flanks of the tool will cut equally. If you angle the compound to 29.5 degrees then the left flank of the tool will do most of the cutting and the right flank will simply produce a clean up cut.


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## savarin (May 15, 2021)

Did you use the fish gauge to set the 60' tool bit square with the work
I cant remember if the spring pass question was answered but thats just a couple of passes without advancing the tool to ensure the tool or work didnt deflect any and thus not cut to full depth.
Something I have done in the past with a crappy cut thread was to spin it reasonably fast and apply a wire wheel spinning the opposite direction for a second or two then reverse both thread and tool directions and do it again to sort of polish the thread flanks and tips.


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## ttabbal (May 15, 2021)

The  'Fish Tail' 60 Degree Thread Gauge
					

I'll start with a simple tool. The 60 degree thread set up tool thats referred to as the fish tail. I've used the tool to set up my lathe bit to cut threads. I have successfully cut threads on the lathe & have compared my cut threads to some " professional" cut threads & could not see any...




					www.hobby-machinist.com
				




I haven't seen anyone post a pic of the tool against the work. That thread shows the other use of the fishtail gauge, aligning the tool and the work. Regardless of how you advance the tool, compound or cross feed, you need to have the tool hitting the work properly. 

You may have done it, but just covering the basics to be sure.


----------



## NC Rick (May 16, 2021)

FTlatheworks said:


> Ya it took a long time. I used a hss 3/8 blank. Now I know if I invest in fact tooling it will only get better. I calculate the sfm and came up with about 500 rpm. Can anyone confirm that’s correct?
> 
> on your project, do you have a tailstock die holder? I hear that’s a guaranteed way to do it.


I do have and used a tailstock die holder.  I also turned the diameter down to less than the 75% size (i think i went to 0.295”). And while it cut clean, i had to turn the chuck by hand (scared to try power feed…) and break the chip every 1/4 turn where it would say “snap!”.  I was attempting to make turn buckles and have left hand tap and die for 5/16”. My lathe is setup for metric threads.  The project sounded easy.  It felt hard so i did what i do and quit


----------



## macardoso (May 17, 2021)

JimDawson said:


> Great start.    You are almost there.
> 
> It kind of looks like your thread is not formed correctly and maybe are cutting too much on the back side..  The top of the threads seem to be folded over away from the chuck. The bottom of the threads look to be well formed.  It's hard to tell but the front and back side angle does not look symmetrical.  Also looks like it is cut too deep.  What might help you is to take a few passes with a file before you take the final couple of threading passes, that should eliminate the folded over sharp tops and give you a more visually pleasing thread form.  It almost looks like your cutting edge is not exactly perpendicular to the work.
> 
> ...


I have struggled with this on my lathe since the beginning. Added a bronze thrust washer to the leadscrew to take up end play and it made a significant difference.


----------



## macardoso (May 17, 2021)

I would have concern that the tool was rotated with the compound and is no longer square to the work.

If you thread using the compound to advance the cut (I do not) then the tool should remain square to the work and be fed into the cut at the compound angle.


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## mksj (May 17, 2021)

I would suggest you give the Carmex lay down inserts with a 5/8" right hand external thread holder a try if threading toward the chuck. I would not cheap out on the inserts, the Carmex are about $16 each, I would get two, I am still using my first insert for 2+ years.  You might also look into David's book "Introduction to Indexable Tooling for the Metal Lathe", lots of good points and specific recommendations for the holders and inserts.








						Primer on Indexible Tooling for Lathes
					

I'm about 3 days into the cleanup of a new to me lathe. Running a mill for almost a year and I find lathe tooling bewildering. And the prospect of grinding my own tools is something I maybe should learn...but the odds of that happening are about -27%.  I've asked around and searched this and...




					www.hobby-machinist.com
				




Very simple to setup, and you get very clean cutting. David and I do quite a bit of threading in a wide range of materials and the laydown threading inserts have given very good results. You first need to make sure your cutting tip is at the right height and parallel to the chuck. To get it parallel to the chuck, I use a 123 chuck against the  chuck face and bring the tool holder up against the other side of the 123 block and then tighten down your tool post nut.  I use the compound locked, doesn't matter what the angle is, I feed each pass with the cross slide. I would at first cut a wider relief groove until you get more proficient and try increasing your threading RPM if using carbide inserts (I would start with 100-120 RPM depending on your gearing). Dimension your rod to the OD of the major thread diameter.

When you start threading, zero your cross slide dial at "0" when the tip of the cutter touches the OD of the rod. I typically take a series of continuous passes at sequential 0.01" depths until I am close to my target depth, then 0.005" and 0.002" and check the nut fit. You will almost always find the minor diameter will need to be a few thousandths deeper than what the dial indicates (i.e. the expected minor diameter). It also depends on the amount of flex in your work, on threading smaller rod I use a live center. You may need to use a fine file to take off the tips of the threads. A spring pass is done as a final pass, usually at the same diameter or 0.001" which should give you a very clean thread. Do not repeat spring passes as it will cause chatter and work harden some materials. You should be able to end up with threads similar to below.


----------



## aliva (May 21, 2021)

I've threaded a lot of 316L SS. using a lay flat carbide insert with oil. I usually turn at around 200 rpm, I've yet to have a problem. Be sure the insert is in good condition.


----------



## FTlatheworks (May 25, 2021)

I’ve been gone for a while. I have not tried again. Can someone explain how to measure the angle the compound is at? I measured 30 degrees from the chuck to the compound and it was the same as my import lathes scale. I can’t for the life of me figure out why, or how you would measure differently.


----------



## FTlatheworks (May 25, 2021)

mksj said:


> I would suggest you give the Carmex lay down inserts with a 5/8" right hand external thread holder a try if threading toward the chuck. I would not cheap out on the inserts, the Carmex are about $16 each, I would get two, I am still using my first insert for 2+ years.  You might also look into David's book "Introduction to Indexable Tooling for the Metal Lathe", lots of good points and specific recommendations for the holders and inserts.
> 
> 
> 
> ...


Those are beautiful threads, good job.
Initially I planned on buying a thread cutting insert as the easy way out. I can’t easily afford to do that, but thought I would save in the time it took and destroying blanks. After joining this forum and multiple members telling me they accomplish it with a hss blank. I decided I want to learn how to do everything the old school, and the toughest way possible. This way if I have the money to buy nicer tools, I will know that it’s my skills accomplishing the task and not my money.

I have been guilty of throwing money at problems and trying to take shortcuts. I don’t what you to think that I believe you, or David are taking shortcuts with carbide inserts, but for me that’s what it was in my mind.

I have made a deal with myself. Once I accomplish SS 304 threads with my own hss bit  successfully, then I will allocate the money for nicer inserts to save myself time and money producing parts.


----------



## rwm (May 25, 2021)

If the compound is perpendicular to the axis of the work, that should be 0 deg (some lathes mark that as 90 deg). From 0, rotate the compound CCW until it is rotated 29.5 deg. Brino was correct that your threads show incorrect angle setting. If you post an overhead pic of the compound setting that would clear things up.
Robert


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## FTlatheworks (May 26, 2021)

rwm said:


> If the compound is perpendicular to the axis of the work, that should be 0 deg (some lathes mark that as 90 deg). From 0, rotate the compound CCW until it is rotated 29.5 deg. Brino was correct that your threads show incorrect angle setting. If you post an overhead pic of the compound setting that would clear things up.
> Robert


I will post a picture, but it is marked at 0 when perpendicular and 45 it is parallel, or linear with respect to the head/tail stock.


----------



## brino (May 26, 2021)

FTlatheworks said:


> I will post a picture, but it is marked at 0 when perpendicular and 45 it is parallel, or linear with respect to the head/tail stock.



I hope that's a mistake!
..........45 degrees when parallel to the ways?
That should be 90 degrees right?

Either that or it's NOT calibrated in degrees, but 2 degree increments.

-brino


----------



## FTlatheworks (May 26, 2021)

brino said:


> I hope that's a mistake!
> ..........45 degrees when parallel to the ways?
> That should be 90 degrees right?
> 
> ...


Ya that’s a dumb mistake. I promise I know trig lol.


----------



## WobblyHand (May 26, 2021)

@FTlatheworks Should look like this:


Hope this helps.


----------



## FTlatheworks (May 26, 2021)

FTlatheworks said:


> I will post a picture, but it is marked at 0 when perpendicular and 45 it is parallel, or linear with respect to the head/tail stock.


Past the 45 mark on the scale is parallel


WobblyHand said:


> @FTlatheworks Should look like this:
> View attachment 367306
> 
> Hope this helps.


I had it backwards then. I can’t read your scale though.


----------



## mikey (May 26, 2021)

See post #4 of this thread to see what your compound angles should be set to.


----------



## rwm (May 26, 2021)

That pic explains a few things! I can't believe you could cut any thread like that. Rotate your compound back to pass your zero mark and then keep going until you get to 60.5 deg. That should be the correct angle on your machine.
Your machine is labeled like mine such that 0 deg is parallel to the bed. That is non-standard.
By the way, we are NOT referring to the tool angle. We are referring to the axis of compound travel. Is that the point of confusion?
R


----------



## Illinoyance (May 26, 2021)

Check Shars for threading tools.  They have on-edge inserts in negative, positive, and neutral rake that all fit the same holder.  They have laydown inserts ant holders for them.  If chipping is your problem you might try HSS or cobalt alloy tools at the appropriate SFM.


----------



## FTlatheworks (May 27, 2021)

rwm said:


> That pic explains a few things! I can't believe you could cut any thread like that. Rotate your compound back to pass your zero mark and then keep going until you get to 60.5 deg. That should be the correct angle on your machine.
> Your machine is labeled like mine such that 0 deg is parallel to the bed. That is non-standard.
> By the way, we are NOT referring to the tool angle. We are referring to the axis of compound travel. Is that the point of confusion?
> R


So I should rotate the compound adjustment dial to the right, or towards the tail stock until it is lined up with what would be on out import machine 60.5 degrees.

can anyone explain with pictures how to precisely measure angle of compound slide axis. I was measuring from the tool and that makes sense to me. Once I figure the correct way to measure and I restore my new machine... lol, I will put new badges and scales on everything similar to davids 1340. It will be nowhere near as awesome as his, but I will try.


----------



## jwmelvin (May 27, 2021)

FTlatheworks said:


> can anyone explain with pictures how to precisely measure angle of compound slide axis.



One way is to use angle gauge blocks between the chuck face and the compound. Or a protractor between those same surfaces. 

For higher precision (not necessary for threading) you can set up a couple indicators and determine the slope of the compound as the carriage moves. One measures carriage travel (z) and the other measures perpendicular (aligned with the cross slide) to the compound’s side surface (x). The angle is arctan(x/z).

Edit: that formula gives the angle from the carriage ways. If you want the angle from the cross-slide ways, you’d subtract that from 90. Same issue that started this thread, if I remember.


----------



## ttabbal (May 27, 2021)

A great way to accurately set the angle of the compound. I don't think you need it for threading, but just to verify, it might be helpful. He has a few interesting videos on threading as well. 

Keep in mind, the TOOL needs to be perpendicular to the work. The Compound can be 30 degrees or whatever, but the tool has to be lined up.


----------



## jwmelvin (May 27, 2021)

^ that’s much better, using the compound slide to determine one leg (the hypotenuse) and the cross slide w/indicator to determine the other leg.


----------



## rwm (May 27, 2021)

Please see Mikey's post. That illustrates it very well.
R


----------



## FTlatheworks (Jun 1, 2021)

There are so many posts from helpful people. I’m not used to having this many responses. It’s great, but I need to be more mindful of the answer given. Thanks everyone for the help. Hands down best forum and people, this I’m sure of.


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## FTlatheworks (Jun 5, 2021)

I’m confused still! If we move the compound to 60.2, or 29.5, why are we moving the tool post? This is at 60.2. What else needs to happen here?


----------



## brino (Jun 5, 2021)

FTlatheworks said:


> What else needs to happen here?



The tool post needs to be rotated such that the tool is square to the work.
I use a "fish-tail" gauge:



put one long flat side against the workpiece and then rotate the tool post such that the 60 degree point fits well in notch on the other side.
Lock the tool post and leave it there for the duration of threading.
The top slide controls the infeed.
After a scratch-cut to double check gearing, advance it a couple thou. per pass to start. The infeed should decrease per pass as each additional cut has more of the cutting tool against the work.

-brino


----------



## WobblyHand (Jun 5, 2021)

@FTlatheworks  Once you have figured out how to position the compound and the tool, here is an additional tip.  If you have long thin stock, like in your recent picture, it's good to use a center drill to make a 60 degree cone in the end of the workpiece so you can use your tailstock (with a live or dead center) to support the end.  If the workpiece sticks out more than 4 x the diameter, it tends to deflect under the pressure of cutting.  That means your threads will not be uniform depth, and your workpiece may not be uniform diameter.  For very long thin stock you may need to use a follow rest.

If you try to cheat the 4x number, like I did recently, you will find your threads will be tighter on one end than the other.  In my case, the only way I could fix it was to chase it with a die.

Good luck single point threading.  It's pretty enjoyable once you get the hang of it.  I struggled with it initially, but finally got it sorted.  You will figure it out soon.


----------



## FTlatheworks (Jun 5, 2021)

WobblyHand said:


> @FTlatheworks  Once you have figured out how to position the compound and the tool, here is an additional tip.  If you have long thin stock, like in your recent picture, it's good to use a center drill to make a 60 degree cone in the end of the workpiece so you can use your tailstock (with a live or dead center) to support the end.  If the workpiece sticks out more than 4 x the diameter, it tends to deflect under the pressure of cutting.  That means your threads will not be uniform depth, and your workpiece may not be uniform diameter.  For very long thin stock you may need to use a follow rest.
> 
> If you try to cheat the 4x number, like I did recently, you will find your threads will be tighter on one end than the other.  In my case, the only way I could fix it was to chase it with a die.
> 
> Good luck single point threading.  It's pretty enjoyable once you get the hang of it.  I struggled with it initially, but finally got it sorted.  You will figure it out soon.


I use a dead center as often as I can. I will be sure to do that with threads too. thank you!


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## FTlatheworks (Jun 5, 2021)

brino said:


> The tool post needs to be rotated such that the tool is square to the work.
> I use a "fish-tail" gauge:
> View attachment 368271
> 
> ...


I thought I should be locking the carriage and using power feed. Man, I am confused. I was cutting threads in softer materials before this that looked normal.


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## FTlatheworks (Jun 5, 2021)

instead of moving compound for depth move the top slide for finer depth control is all your saying. I still don’t understand why it wouldn’t be easier to leave the tool post where it is and just achieve the angle you need with the compound angle adjustment.


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## FTlatheworks (Jun 5, 2021)

How this?


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## BladesIIB (Jun 5, 2021)

FTlatheworks said:


> How this?


I have not read this whole thread but looking at that pic you seem squared up well enough with your tool but I would recommend pulling it into the tool holder some. It is sticking out further than needed which could introduce chatter.


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## FTlatheworks (Jun 6, 2021)

Holy cow, never mind. I’m gonna do it the exact way you said. It was like cutting through butter lol.


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## FTlatheworks (Jun 6, 2021)

BladesIIB said:


> I have not read this whole thread but looking at that pic you seem squared up well enough with your tool but I would recommend pulling it into the tool holder some. It is sticking out further than needed which could introduce chatter.


Ok, I will do that. I was only running that way because when I was setup the wrong way the tool holder would get to close to things.


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## brino (Jun 6, 2021)

@FTlatheworks 

Congratulations! 
It looks like your persistence got you there. Well Done.

Just a couple things:

First, as @BladesIIB said reduce that tool hang-out for less vibration.




FTlatheworks said:


> instead of moving compound for depth move the top slide for finer depth control is all your saying. I still don’t understand why it wouldn’t be easier to leave the tool post where it is and just achieve the angle you need with the compound angle adjustment.



First some terminology. Compound = top-slide. They are the same thing.

We are using the compound (top-slide) angle adjustment to set the angle we want to feed the tool into the cut.
In this case by feeding in with the compound the tool kind of slides in at an angle rather than straight in.
This allows it to only cut on the left-hand leading edge (when feeding towards the headstock, tool at front, top of the work rotating towards you).

I find on my light and kinda loose Southbend 9" lathe this works much better than feeding straight in using the cross-slide.
When I try infeed with the cross slide the cutting forces are higher due to both side faces of the tool contacting the work-piece.



FTlatheworks said:


> I thought I should be locking the carriage and using power feed.



Yes absolutely we do lock the half-nuts to the lead-screw and use the lathe gearing to move the tool precisely for every rotation of the spindle.

This maybe confusion between terms again; longitudinal "carriage" feed vs. tool infeed.
The lathe will power feed the tool (indeed the entire carriage) left and right.
Our tool infeed really controls the depth of each cut. For threading we can start with larger infeeds , but as the cutting progresses the tool bit gets deeper into the work-piece and does more work, so we can relieve a little of the stress my feeding the tool bit in less.

I often start threading with 2-5 thou. infeed but it can be different for each lathe, tool bit and work-piece material.
I might try up to 10 thou. to start if I know the tools and material.
Threading often ends at 1 thou. infeed when you are getting close to final size.
Then one or two "spring passes" are done with no additional infeed. This helps to clean up the threads.

In normal outside diameter turning we usually infeed with the cross-slide....but here too you could use the compound set an an angle for infeed. Just beware that the numbers on the cross-slide dial will no longer indicate the true infeed. But it can be calculated using trig and the angle of the compound. This is sometimes used when you want very fine infeeds, like when trying to remove sub-thou. of material with a shear tool.

For threading either the compound (top-slide) or cross slide can be used for infeed.
I just find the cross-slide gives me better results on my lathe.

I'd recommend that as you get more comfortable with single-point threading you give both a try and see what works best for you.

-brino


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## FTlatheworks (Jun 6, 2021)

brino said:


> @FTlatheworks
> 
> Congratulations!
> It looks like your persistence got you there. Well Done.
> ...


Yes, I should have reread before I posted. I’m not sure why I conflating top,cross,and compound. It sounds like you knew understood where I was going though. Thank you for the support.


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## FTlatheworks (Jun 7, 2021)

Well, crappy night. I tried to thread a part that I machined in the wrong order. It was too small and I should have cut threads first.
I thought I could handle it without crashing the tool post into the chuck. The tool post hit the chuck and the press stalled. I hit the brake and tried to disengage half nut, but it wouldn’t budge. I had to turn chuck in reverse with the chuck tool to disengage half nut. I Then took the tool post off. Nothing seems to be broken, but I’m worried about what damage I may have done. The tools post and two of the jaws have the face ground off.The threading tool nearly cut .100 deep in a .437 diameter piece of stainless. My question is how did it cut that deep if it was set to do a scratch pass?  What could flex that much to make the tool cut that deep?
It clearly pushed the post and the top slide down and into the work, but what flexed enough for that to happen? Did I bend something. I will post pics of chuck and tool post tomorrow.


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## brino (Jun 7, 2021)

My guess is that the tool post rotated into the work after contacting the chuck.
It was then likely sprung down and the work sprung up over it.

I would check the half nuts. 
Perhaps you can see them with a flashlight and mirror.
If not, maybe just test them by cutting a few more threads.

You may have gotten away with no real damage other than some marks on the tool post and chuck jaws ........ and to your pride.

These are the type of issue that make me glad I have a flat belt that I can slacken just a little if there's a chance something goes wrong.
Like a fuse in the system, it prevents any major damage.

-brino


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## FTlatheworks (Jun 7, 2021)

brino said:


> My guess is that the tool post rotated into the work after contacting the chuck.
> It was then likely sprung down and the work sprung up over it.
> 
> I would check the half nuts.
> ...


What am I looking for on the half nuts? I looked at them from the sides of the carriage, can’t see much from there though.


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## BladesIIB (Jun 7, 2021)

Sorry about your crash. Sounds like you cleaned most of it up well. I think one quick way to test the half nuts would be to move to different spots on the lead screw and feel and observe how they clamp. Can be non running for this just seeing if they engage clean and smooth. Maybe move the hand wheel and see if any play after engaged. If they engage clean in multiple places including where the crash occurred then I think that would eliminate the concern for any major damage?  Have not tried this so curious what others think would be a good check.


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## FTlatheworks (Jun 7, 2021)

I sanded the sharp edges off on the tool post.
Could the lead screw have bent from that, or do they usually have some perceptible wobble to them?


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## brino (Jun 8, 2021)

FTlatheworks said:


> What am I looking for on the half nuts? I looked at them from the sides of the carriage, can’t see much from there though.



It depends on the lathe, and how much room there is between the apron and the bed whether you can get a light and mirror in there.
Best case you can look at the half-nut tooth profile and see an acme thread like profile and then move on.

However you may need to fall-back to some functional tests.
I would NOT immediately disassemble (remove the carriage) I would:
1) with the machine off lock the half-nuts put an indicator against the carriage and see how much "slop" you have when you manually push the carriage left and right. Then the question becomes how much is too much "slop".
2) cut some more threads as a test. In this case small slop won't matter. It is a gross test to see if the half-nuts are completely stripped.

Last resort is if all the above fail to give any reassurance. Then pull the carriage, or at least the half nuts off to look for damage.
Hopefully it does not come to this.

-brino


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