[TheForge] Punching holes with Hydrolic press

[Bob Ehrenberger]

Andy,

Thanks for the input.  I tightened up the tolarance on the botom die, but it 
galled when in use.  Probably because it is just mild steel and would stick 
to the sheet metal being punched.  I think that I either need to open it 
back up the .030 or make one out of tool steel with .010 clearance.

Robert Ehrenberger
Shelbyville, Mo.
eforge at centurytel.net

----- Original Message ----- 
From: "Andrew Vida" <osan at netlabs.net>
To: "Bob Ehrenberger" <eforge at centurytel.net>; "Blacksmithing List Sponsored 
by ABANA" <theforge at mailman.qth.net>
Sent: Wednesday, October 05, 2011 5:59 PM
Subject: Re: [TheForge] Punching holes with Hydrolic press




On 10/4/2011 2:22 PM, Bob Ehrenberger wrote:
> The
> only problem is that the material sticks to the punch and has to be 
> knocked
> off after raising it up.  It's a whole lot easier than drilling big holes 
> in
> thin material.

Your clearance is too large.  I'd keep it to 0.010".  Also, a 1* or 2*
negative draft angle for clearance with perhaps a 0.30" margin, like so:

          |          |
          |___    ___|
             /    \
            /      \<--- 2* - 4* included relief
            |______|<--- Margin

The margin serves two purposes: it strengthens the edge and provides
some allowance to redress the punch for wear.



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