Machining M2 tool steel

Kenre · Jan 31, 2020

Manual lathe turning 9mm Dia full hardened M2 HSS down to 4mm Dia 3mm long.

No coolant, using cheap WMNG inserts, which work ok. Should i be worried about stressing or weakening the material? Finished Pins are under a bit of stress so i dont want to weaken it with the turning. They will be finished ground to size.

If turning is fine, whats a recommended insert ? May put the job in the cnc.

RJT · Jan 31, 2020

If they are going to be ground anyway, why not skip the hard turning and just grind them? If you are going to turn them , use CBN and several light cuts in a solid setup CNC and finish them. I would get away from two different operations. Either way, if you don't get them hot enough to temper them, removing material won't change anything.

Mtndew · Jan 31, 2020

Kenre said:
Manual lathe turning 9mm Dia full hardened M2 HSS down to 4mm Dia 3mm long.

No coolant, using cheap WMNG inserts, which work ok. Should i be worried about stressing or weakening the material? Finished Pins are under a bit of stress so i dont want to weaken it with the turning. They will be finished ground to size.

If turning is fine, whats a recommended insert ? May put the job in the cnc.

Just watch how hot you get it, and I would recommend CBN like the guy above me.

Rickyb · Jan 31, 2020

Or the Cadillac version, PCD.

Kenre · Feb 1, 2020

I thought PCD was for non ferrous only?

Reason i want to turn most of the material off is to reduce the amount ground. Only have one wheel atm and last lot of pins i had to redress the wheel every 3 or 4, I have a max radius i need to hold.
Doing about 100 this time.

Might give a CBN in the cnc a go. Are they best run dry or with coolant?

tnmgcarbide · Feb 1, 2020

i use this grade on hard steel ,
google search -
Valenite Ceramic Inserts TNG432T00630 Q32

BSCustoms · Feb 1, 2020

CBN will do beautiful for you. Yes run dry and follow whichever brand you go withs recommendation.

PCD is not for carbon based materials as the high heat can actually pull the diamond and prematurely wear the tool.

Mtndew · Feb 4, 2020

Rickyb said:
Or the Cadillac version, PCD.

No, that's not for steel.

RJT · Feb 4, 2020

Yes, as others have said PCD is not for steel. Use CBN and finish it. If it is not an interrupted cut, you should be able to finish it without grinding. We do a lot of hard turning with CBN or ceramic inserts. Grind if there is a key way or cross hole, otherwise turn it finished. Just make sure you have a really solid setup with nothing flexing.

Milland · Feb 4, 2020

BSCustoms said:
PCD is not for carbon based materials as the high heat can actually pull the diamond and prematurely wear the tool.

Yes, but to clarify a little, carbon atoms (which are in a crystalline structure in diamond) are very readily soluble in iron and steel at high temperature, so the cutting edge of PCB gets broken down relatively quickly as it rubs against steel workpieces (the cobalt binder in most PCD inserts offers some protection, but not a lot).

That said, I've used diamond edges on hard steels when I had to "make due", and for limited time use it works. But I agree with those saying CBN would be a good choice for the OP's needs.

Edit: Here's some information on PCD vs CVD diamond cutting tools, but nothing specific on "not for steel": Diamond – PCD or CVD? - telcon

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Machining M2 tool steel

Kenre

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RJT

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Mtndew

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Rickyb

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Kenre

Cast Iron

tnmgcarbide

Diamond

BSCustoms

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Mtndew

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RJT

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Milland

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