We use all 5 sizes of import specials from Horrible Freight in lab
classes on 24ga galvanized and 16 ga aluminum all the time. The largest
HF goes to 1-3/8"
http://www.harborfreight.com/cpi/cta...emnumber=91616
http://www.harborfreight.com/cpi/cta...emnumber=96275
One of my students was running them on 1/4" steel without too much issue.

MUCH safer for thin metals (no lift, no great tendency to grab and spin)

Michael Koblic wrote:
spaco wrote:
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.
----------------------------
These work great for punching holes in rubber, leather, canvas, etc.,
too.

This sounds useful.
How much metal distortion is there? And what is the biggest hole you ever
made this way? Did you have to heat-treat the sharp end?