Request for hard gear shaving

[gearman1234]

I have a gear to be shaved with profile and a lead crowning. The material is 4140. Gear Data 30T, 12 dp, 14.5 PA, Standard tooth thicknes,The base hardness required is 28/32. Since the batch qty is very less I am thinking of shaving the gear, thru' harden to 28/32 and induction harden to 50/55 as per dwg. Th dwg requirements are base hardness 28/32 and teeth hardness 50/55.

I was just wondering how much distortion would be there with double heat treatment. Required finish gear quality is AGMA 8, which is not stringent.

If I start with having heat treated material 4140 with 28/32 hardness and then hob it and shave it and then induction hardnen it, I may have a problem in shaving 32 Rc hard gear and the shaving cutter may not retain the profile. That is what is my opinion. If anybody else has any experience with shaving hard gears upto 32 Rc, then I would like to know about their experience.

 

[carburized]

gearman1234

Yes, you can start with 4140 material as it comes in 28/32 RC. We are gear manufacturers and do this all the time. Hob it, shave it and then you can Nitride it and induction harden it. By Nitridin you will not much distorsion ( may be negligible). Induction harden if done properly, will not contribute to distorsion.

http://www.gearsandbearings.com

Ravi

 

[gearwheel]

Thank you very much.

 

[diamondjim]

Nitriding alone would probably give you
little distortion.
Induction hardening would give you a
harder surface that could be tempered
back to give less distortion.
What is the case depth that you are
looking for?
There are some Swiss Machines that can
hard cut the 55Rc material.
I would assume if you cut to an AGMA 10
and then hardened, I think you would end
up with and AGMA 8 quality gear after
hardening deepening on how deep a case
you are hardening. I am certain you will
have some shrinkage that will have to be
accounted for.

 

[gearman1234]

We need to harden it to depth 0.03/0.09 (measured below root). We are also thinking of finish hobbing it with a special profile hob since it involves crowned profile and then induction harden it. Hobbing quality would have to be AGMA 10 which would get downgraded to AGMA 8 after hardening.

 

[GearmanPE]

This is a small gear, so induction should be sucessful. Consider the frequency, there should be some unhardened core to keep gear ductile. Induction hardening is difficult to control and should be avoided except for cases where you have lots of time to develop the process and process controls.

Carburizing is cheaper and much more reliable. With care, you should be able to acheive Q8 with this process.

 

[gearman1234]

My experience is opposite to yours. Carbursing and hardening induces more distrotions than induction hardening.

Also in the present case I can not carburise as I have 4140 and this is not a carburising steel.