Milling Steel on a Mini Mill

[RaisedByWolves]

We keep talking about heat treat but I would think the proper 41XX alloy might be better, 4140 annealed is a fairly tough stuff without heat treat.

That stuff also work hardens, so failures is a mater of when, not if.

Toughness and hardness are two things people struggle to understand.

Break die steel (4140) is good for wear and fairly easy to machine. It was engineered for a specific purpose though and I’m not sure it fits here.

Ideally I would make these out of D2, hardened snd drawn back to 58 rc and put them in and forget them for the rest of my natural life.

Would probably eat the occasional rock without harm to the blade. Hard and tough, but $$$!

Second would be A2 at about 52rc , which would give good life and be fairly tough, not as hard, but for less money.

Third would be O1, which would need to be left oversize and ground flat after hardening and drawing back. O1 loves to warp and it could come out OK enough to use(.005-.010 warp end-end) or it might need significant grinding to flatten it out.

 

[verbotenwhisky]

That stuff also work hardens, so failures is a mater of when, not if.

Toughness and hardness are two things people struggle to understand.

Break die steel (4140) is good for wear and fairly easy to machine. It was engineered for a specific purpose though and I’m not sure it fits here.

Ideally I would make these out of D2, hardened snd drawn back to 58 rc and put them in and forget them for the rest of my natural life.

Would probably eat the occasional rock without harm to the blade. Hard and tough, but $$$!

Second would be A2 at about 52rc , which would give good life and be fairly tough, not as hard, but for less money.

Third would be O1, which would need to be left oversize and ground flat after hardening and drawing back. O1 loves to warp and it could come out OK enough to use(.005-.010 warp end-end) or it might need significant grinding to flatten it out.

4140 Annealed is a 197HB and would not see those issues yield strength is in the neighborhood of 60KSI....

 

[RaisedByWolves]

4140 Annealed is a 197HB and would not see those issues yield strength is in the neighborhood of 60KSI....

Work hardening can still be an issue, but to what degree in this application I do not know, but I tend to steer clear of high speed unknowns.

I'm unsure of the part in bold so if it has bearing it is out of my realm of experience.

We had dies made with 4140 and they failed miserably and often due to flanges on the steels getting mildly bumped repeatedly over thousands of cycles. We replaced those with A2 and the failures stopped.

In this application it would see thousands of cycles in only minutes of use.

Basically I only know what I know about 4140, so in my experience I cant recommend it.

Any further insight greatly appreciated.

 

[verbotenwhisky]

Work hardening can still be an issue, but to what degree in this application I do not know, but I tend to steer clear of high speed unknowns.

I'm unsure of the part in bold so if it has bearing it is out of my realm of experience.

We had dies made with 4140 and they failed miserably and often due to flanges on the steels getting mildly bumped repeatedly over thousands of cycles. We replaced those with A2 and the failures stopped.

In this application it would see thousands of cycles in only minutes of use.

Basically I only know what I know about 4140, so in my experience I cant recommend it.

Any further insight greatly appreciated.

197 is the brinell hardness, and annealed would be preheat treatment.

 

[RaisedByWolves]

197 is the brinell hardness, and annealed would be preheat treatment.

Ok, I know of Brunel but never worked with it as we only do the RC A/B/C scales.

I thought the 197 might have to do with the steel composition where it would prevent work hardening.

 

[jonesrick]

Thanks. Will do.