# Stress Proof



## tweinke (Jun 5, 2017)

A coworker has a shaft he needs keyways  cut, faced on ends drilled and tapped. Anything I need to know before I start? Most of my work has been in unknownium and whatnot and although I realize the term stress proof without a number may not tell the whole story. Thanks for any input!


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## mikey (Jun 5, 2017)

Are you talking about 1144 Stressproof steel? If so, its good stuff for shafts and such. You machine it like most materials:

Has a hardness of about 17 Rc so maybe semi-hard. It has a gray skin that should be removed in the areas you plan to machine. This stuff machines freely (has about .24% Sulfur so it machines pretty nicely) but requires a rigid setup so keep your stickout from the chuck minimized. Rough this steel slow (cutting speed about 60 sfm) and finish with a light cut as fast as your lathe will go. I normally use HSS with 1144, not inserted tools, to keep work hardening to a minimum.

I suggest keeping your speeds low when drilling, too, with lots of coolant and sharp drills to keep the work cool. Try to keep the drill cutting continuously; don't dwell with the drill or it can get really hard. I normally drill one size larger than the recommended tap drill size so tapping is easy without losing much strength. 

For keyseats, you need a very accurate collet to hold the cutter or your keys will fit loose. Support the work piece rigidly before trying to cut the slot but it should cut with no issues. I like this stuff for leadscrews and shaft and it slots just fine with a sharp Woodruff cutter. 
 Shouldn't be too difficult for you, Tweinke. Just basic shaft work.


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## tweinke (Jun 6, 2017)

Nice to know the inns and outs I will assume its 1144, coworker didn't ask for any specifics when he purchased the shaft. I wondered about work hardening so the info given is much appreciated!


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## 4GSR (Jun 6, 2017)

Stressproof work hardening???  That's a new one to me.

It cuts nice small chips, don't have to worry about stringers!  And it polishes beautiful with a little emery!

But work hardening, I don't think you have to worry about that in stressproof.


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## mikey (Jun 6, 2017)

Sure it does, Ken. I probably use this steel more than is needed because I like to turn it. When I started to use it, I used inserted carbide at recommended speeds and it definitely gets hard if you feed too slow or dwell in the cut. If the work gets hot, taking a very small sizing cut can be difficult. It did this enough that I switched to a HSS tool ground just for this material. I also know that it can harden enough to make tapping difficult if you don't keep the drill cutting. The only 1/4-20 tap I ever broke was in 1144.

It may be that 1144 is more difficult to use on smaller manual lathes. On my Emco lathe, it turns beautifully but on a little lathe you have to know how to work with it.

I've seen enough anecdotal comments on work hardening with 1144 to know that I'm not alone in my findings. If it has enough carbon in it to harden, and 1144 does, then it can get hard when there is a lot of heat at the point of cut.


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## 4GSR (Jun 6, 2017)

I'll have to try to work harden a piece the next time I think about it.

Of course, all the machining I've done on Stressproof or 1144 has been in a 13" or larger lathe.  

Used to have lead screws made from it.  3" OD x 20 to 30 foot long.  Used to have a special one pitch thread cut on the stuff for the full length.  Good old days!


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## mikey (Jun 6, 2017)

I dunno', Ken. Maybe its because I'm a hobbyist but I can, and have, work hardened this stuff enough to pay attention to what I'm doing. I recall the first time I turned this stuff; it was for a slitting saw arbor that was only 3" long. I went through the entire 12" long piece I had to get that arbor because I couldn't get the nose sized correctly. I was trying to take tiny finishing cuts and couldn't get through the surface until I took a file to it and figured out I hardened it. It wasn't a deep layer but enough to make sizing cuts difficult. So, for me, I know that speed matters, HSS works better than carbide at those speeds, and that localized heat is not good.


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## 4GSR (Jun 6, 2017)

Yeah, it has enough carbon and manganese to harden it.  I've just have not encountered it over the years cutting the material.  I've used both HSS and carbide, too.

Must be something in the Hawaiian atmosphere doing it.  Time for a vacation.


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## mikey (Jun 6, 2017)

Funny, I was thinking of saying something about hardening in Hawaiian air! As I look around me, everything is green or blue - not a bad place to be.


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## Alan H. (Sep 19, 2017)

Seemed to have some work hardening going on today at a shoulder that I was repetitively lingering in.   It seemed to get very hard and the bit would squall a little.   I will change my technique on the next piece.  The raw material is 3/4" dia. 1144 with 100 ksi yield and RC 25 hardness from McMaster.  It cuts well and the finish is okay.   BTW, the hardness appears to be greatest at and near the surface.

Mike, you mentioned stripping the gray off before you machine it.  How do you do that?   Just skim it off?   I want to knurl the big end and sounds like I need to get that gray off first at a minimum, is that correct?

Here's a photo of the piece I am talking about.


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## mikey (Sep 20, 2017)

Alan H said:


> Seemed to have some work hardening going on today at a shoulder that I was repetitively lingering in.   It seemed to get very hard and the bit would squall a little.   I will change my technique on the next piece.  The raw material is 3/4" dia. 1144 with 100 ksi yield and RC 25 hardness from McMaster.  It cuts well and the finish is okay.   BTW, the hardness appears to be greatest at and near the surface.
> 
> Mike, you mentioned stripping the gray off before you machine it.  How do you do that?   Just skim it off?   I want to knurl the big end and sounds like I need to get that gray off first at a minimum, is that correct?



Yeah, I've found that the skin is rather hard so get under it and skin it off. I just take a 0.010" deep cut and that usually does it; if not, go a little deeper. If you're going to skin it and then knurl, I would skin the gray off and then take a tiny cut, maybe 0.002" deep at high speed with a sharp tool. This will give you a nice satin finish that you can lay a nice knurl down on.

Edit: I should add that if you're going to knurl this stuff, do it like you mean it. By that, I mean to get your knurl to maybe 90% of full depth and cut it in a single pass. If you try to make repeated passes in this stuff it may not allow you to get to full depth. Form-Rol, the knurl company, recommends you consider 90% depth a full depth; beyond that, they consider it to be over-rolling the knurl and this can damage your knurls. I do hope you have a robust knurler for this job.


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## Alan H. (Sep 20, 2017)

Thanks Mike, I understand what you are saying about the knurling.  I suspect that if you roll over this stuff too much and you can forget it. 

I am going to "put the squeeze on it" as you suggest.  I  am hoping my knurler is up to the job:


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## benmychree (Sep 20, 2017)

4gsr said:


> Stressproof work hardening???  That's a new one to me.
> 
> It cuts nice small chips, don't have to worry about stringers!  And it polishes beautiful with a little emery!
> 
> But work hardening, I don't think you have to worry about that in stressproof.


I quite agree about there being no problem with work hardening, I have machined a lot of it, and never saw a problem; it is quite easy to machine in all respects, the main advantage with it is its stability under machining proceedures; you can cut a full length keyway in it without the tendency to bow as with CRS.  Only thing I learned about it is not to use it in a high torque situation with shock loading, it will come apart.


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## mikey (Sep 20, 2017)

Alan H said:


> Thanks Mike, I understand what you are saying about the knurling.  I suspect that if you roll over this stuff too much and you can forget it.
> 
> I am going to "put the squeeze on it" as you suggest.  I  am hoping my knurler is up to the job:
> 
> View attachment 242133



That is probably one of the best knurlers made and it is more than up to the task.


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## Wreck™Wreck (Sep 22, 2017)

Stress Proof is a registered trademark of the  Niagara Lesalle  Corp.

It is an excellent material to turn which is one of the reasons why it was developed, the manufacturing process makes it very consistent from bar to bar. If you make many parts you will appreciate this, you will also pay a bit more for it.

I also have never had it work harden and am not sure that is even possible in lathe work. But what do I know?


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## benmychree (Sep 22, 2017)

Wreck™Wreck said:


> Stress Proof is a registered trademark of the  Niagara Lesalle  Corp.
> 
> It is an excellent material to turn which is one of the reasons why it was developed, the manufacturing process makes it very consistent from bar to bar. If you make many parts you will appreciate this, you will also pay a bit more for it.
> 
> I also have never had it work harden and am not sure that is even possible in lathe work. But what do I know?


They also made "Fatigue Proof", and I think "ETD 150", something like 4140 HT of 150,000 tensile strength, but easy to machine like the other two.


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## 4GSR (Sep 22, 2017)

A word of thought,  Stressproof is not used in the oilfield at all for most any applications.  You will not find it used for any tool that goes into the ground in the oilfield! Hydrogen Sulfide or any acid will make Stressproof look like a piece of Swiss cheese almost over night!


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## benmychree (Sep 22, 2017)

4gsr said:


> A word of thought,  Stressproof is not used in the oilfield at all for most any applications.  You will not find it used for any tool that goes into the ground in the oilfield! Hydrogen Sulfide or any acid will make Stressproof look like a piece of Swiss cheese almost over night!


Not to mention its tendency to come apart under torsional shock loading.


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## Silverbullet (Sep 23, 2017)

Use plenty of coolant on the cutting and knurling +it will help the knurls work and look better..


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