How much clearance for a bell punch?

[carlroscoe]

I'd like to make a bell punch with a 1/2" dia. hole for the punch. Can someone give me some advice on how much smaller the diameter of the punch should be relative to the hole it will slide in? Also, should I be concerned about distortion of the punch from hardening it and, if so, how should I address that issue?

Thanks for any help!

 

[Martin W]

I have been told for mild steel that material thickness x .200 will give you the clearance for a punch. eg. material .060" x .2 =.012 clearance . I think you would need more clearance for aluminum . Could you grind the punch to size after hardening? tool post grinder?
Cheers
Martin
Edit- I misunderstood. I thought this was for a punch press. disregard the above.

 

[benmychree]

What are you calling a bell punch?

 

[carlroscoe]

A bell center punch, sorry

 

[benmychree]

One thou would be plenty of clearence, only the very tip need be hardened, to avoid distortion or the need to grind the whole shank.

 

[carlroscoe]

Thanks much!