DIY square hole punch press

[Paul Alciatore]

I am afraid I have to disagree about the reason for no other shapes than round. The Roper-Whitney tools cost a fortune and could easily be modified to allow both the needed angular alignment with a tool free change-over and the precision needed for them to work properly. I think the real reason for this is that these hand punch tools, the R-W and the many copies of it, have a limiting diameter of about 1/4". These punches work by shearing the entire circumference at one time. So larger diameters, larger sizes would require that a longer edge would have to be sheared at once and that would take a proportionally larger amount of force. The length of the circumference of a 1/4" circle is a bit over 3/4" and that is about what these tools are capable of shearing. The fact is, that there is very little call for holes other than round that are smaller than 1/4". I have cut many, many holes in sheet metal for switches, lights, and other components and have never needed a 1/4" or smaller "D" or square or any other shape than round hole. So the reason why these hand tools do not have shapes other than round is that there is no need for small ones and the tool is not capable of the force needed for larger ones.

Greenlee makes a line of chassis punches that come in sizes from 1/2" and up. I have a collection of round ones from 1/2" up to a bit over 2" in diameter as well as several square ones, a couple of rectangular ones, "D" shaped, double "D" shape, and some others that are specific to particular electronic connectors, like the sub-D series. These chassis punches use a central draw bolt with a nut. The non-round ones use some kind of key on that draw bolt to provide the needed alignment.

Oh, one other thing, these chassis punches do not attempt to shear the entire perimeter of the shape at one time. They incorporate an angled edge on the punch that starts at two opposite points and cut at only two places at at time. But it takes a longer stroke of about 3/8" to 5/8" for the full cut. In this way, the amount of cutting force is greatly reduced. In fact, I have measured the force they need and found that a 2" diameter hole can be cut with about the same amount of force as a 1/2" diameter. Both of those punches only cut at two places at a time. It would be impractical and expensive to modify the R-W style hand punch tools for such a long stroke so that approach could not be taken with them.

I obtained this collection of chassis punches by purchasing lots of used punches on E-Bay. I usually had to sharpen them, but that is easy once you know how. By purchasing several collections, sharpening them, and then selling any duplicate sizes that I wound up with, I was able to get the collection at a greatly reduced price, almost for free. I am sure that this could still be done today and it would be an excellent way to get a collection of punches.

Cool results, and rather surprising as well. Removing the chamfer on sockets [die] will clean up results more than same effort on extensions [punch].
The hand punch copies the Roper-Whitney Jr.; in every HVAC and duct workers box. The reason 'shaped' dies aren't made for it is twofold.
One is that neither punch or die can be fit in a tool-free change over for critical alignment. Those gauges of material matching punch capabilities are down in range of .005" and less per side, which relate to second impasse.
You'll notice, screwing in the die can position itself any height allowed by it's thread length. At extremes that prevent enough travel or such a large gap of the handles no grip could span. Limits on round sets are far less.

And to RalphXYZ: Ratchet and regular sockets are close in hardness, quality impacts are far tougher by use of shock resistant steels. Both are through hardened, thin walls and case hardening will be a brittle combination, especially in the various corners.