[TheForge] Punch press dies

[Bob Ehrenberger]

Ries,

Thanks for your reply. Yes, that is what I want to do.

I have a home made press and was planning on making my own punches and dies. 
Right now most of my sheetmetal work is in 16 ga and 14ga material.  I don't 
expect to go past 1/4" plate.

I have already made a holder for 1" rd tools, it is a pretty loose fit, I 
hold the top tools in place with a set screw. I chose 1" rd because that is 
the same size my kick press uses, and the top tools could be interchanged. I 
have already made 3 round tools for making bowels and plates, 5 different 
sizes of fullers for making grooves and creases in sheetmetal, and a veining 
tool.

Drilling large holes in light sheet is a pain because it tends to bind, so I 
thought it would be nice to be able to punch them. I also make several 
sconces that have key holes for hangers, which require drilling and filing 
also a pain. A key hole shaped punch would save a lot of time.

It sounds like 1/32" clearance or a little less would work. I was concerned 
that if it was too close the punch would get stuck.

Robert Ehrenberger
Shelbyville, Mo.
eforge at centurytel.net


----- Original Message ----- 
From: "Ries Niemi" <rniemi at fidalgo.net>
To: "Bob Ehrenberger" <eforge at centurytel.net>; "Blacksmithing List Sponsored 
by ABANA" <theforge at mailman.qth.net>
Sent: Monday, July 18, 2011 2:37 PM
Subject: Re: [TheForge] Punch press dies



On Jul 18, 2011, at 10:45 AM, 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?

Robert Ehrenberger
Shelbyville, Mo.
eforge at centurytel.net

Are you are talking about punches and dies?

If So you want to know "punch clearance".

this varies depending on the material being punched, and the thickness.

Here is a quick chart for mild steel-


CLEARANCE FOR A-36 and MILD STEEL MATERIALS
Recommended clearance for punching

MATERIAL THICKNESS              RECOMMENDED CLEARANCE

1/4" to 1/2" / clearance- /1/32"

1/2" to 3/4" /clearance-  /1/16”

3/4" to 1”  /   clearance-  /   3/32”

1” and over/ clearance-  /1/8”

So, for the vast majority of blacksmith needs, 1/32" total clearance is 
good. That means the punch is 1/32" under the die size.

If you order ironworker punches from someplace like Cleveland punch, they 
will ask you thickness, and size your punch and die accordingly.

If you are asking about the punch holder, that you slide the punch into, it 
can be a loose fit, oversize, just as long as you have set screw that holds 
the punch in place. This works for smooth shank punches, which were used on 
many older, lighter duty punches like pexto, niagara, and whitney. Usually, 
I grease mine, so they will come out again, so clearance is probably .010 or 
so.

A better system is a quick release system, which uses a lock nut to hold the 
punch in, and relies on the lip at the top of the punch to hold the punch in 
place. This is for ironworker style punches, which have that lip on  top. In 
this system, its the accuracy of the threading of the retaining nut that 
centers the punch, not the diameter of the hole and the clearance between 
the hole and punch.

What type of punches will you be using?
homemade, or storebought?
For round, square, and oval holes, storebought are better, and pretty 
reasonably priced. For oddball, specials, you will probably make them 
yourself, but it makes sense to pick a standard size/type so you can 
interchange with commercially available stuff.

there are several major suppliers of punches and dies, and most stock 
coupling nuts as well.
http://www.americanpunchco.com/punch_stems_coupling_nuts.htm


Ries Niemi
Industrial Artist
http://www.riesniemi.com/





Ries Niemi
6988 Bayview Edison Road, Bow, Wa. 98232
360.766.8004
www.riesniemi.com
rniemi at fidalgo.net







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