Stress Proof

[mikey]

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.

 

[Alan H.]

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:

 

[benmychree]

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.

 

[mikey]

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.

 

[Wreck™Wreck]

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?

 

[benmychree]

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.

 

[4GSR]

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!

 

[benmychree]

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.

 

[Silverbullet]

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