In article , spaco wrote:
A friend just asked me how I might go about making 1 1/4" dia. round
holes in the bottoms of tin cans. He was thinking of making a chassis
punch to do the job. He needed an excuse to do something on his South
Bend Lathe.
I suggested making a "Dinker Die", as an easy to do, faster
alternative. I googled "dinker die" to get a .jpg to send him, and
didn't get many hits. This surprised me. I thought everyone knew about
them, but apparently not.
So, here's what I wrote him on the subject (use tool steel if you
want it to last):

Yuh know, us blacksmiths chisel cut sheet steel up to 1/16" thick or
more, cold, with a sharp cold chisel. I have several dozen of these
that I have made. I have a set of them that are curved, so I can
produce radii from about 1/4" to about 2".
You could also turn a "dinker die" in your metal lathe. It's just
a piece of tubing (water pipe, etc.) whose ID is correct for the hole
size. Then you turn a chamfer on the outside of the tubing at about 60
degrees. all the way towards the ID until it is sharp. Just set the
sharp end on the tin, backed with wood, and hit it. You simply punch
out a slug.
I have made many of these over the years. Sometimes its the hole
that I want and sometimes its the slug.

Unless you want the slug, my favorite approach to making holes in thin
sheet stock is a step drill. They will make a nice clean round hole, an
with care, you can even debur the top edge. They are far safer than
twist drills, and you don't get trilobular holes. For a large hole in
thin material, you can use a step drill to make a smaller hole & use a
chassis punch like a Greenlee.

For tin cans, even the Chinese step drills would probably work. For more
serious stuff, McMaster sells TiN coated ones.

Doug White