[TheForge] Punch press dies

[Andrew Vida]

I don't have figures handy at the moment, but a small punch and die set 
should be pretty tight, I might keep it to 0.005" or less... depending 
in part how precise your press is, hole size, and thickness of material 
to be worked.  The smaller the hole and the thinner the material to be 
punched, the tighter the tolerances must be in order to get a good result.

The idea, of course, is to cut by shearing action.  Excessive clearance 
will cause the material to be drawn down into the die, the eventual mode 
of material failure being far more bending and tension than shear.  The 
slug will be distorted as will the sheet/plate from which it has been 
punched.  This may be acceptable in large scale hot work where the hole 
in question will be worked further.  Basically, the more precision you 
desire, the tighter you need the set to be.

On 7/18/2011 1:45 PM, Bob Ehrenberger wrote:
> I'm thinking of making some hole punch dies for my press.  I know that there
> is a formula to determine the clearance between the punch and the bolster.
> Do any of you know how much oversized the bolster needs to be?