Aluminum sign corner rounder

[Bill Gibson]

Now that's (Master Cylinder) pretty clever!!! I bet you could use a Disc brake caliper on the other end for the notcher. Just need a guide for the punch.....
I just used a piece of 2" Schedule 40 pipe and a piece of 2" hot rolled bar.

It cut the same as yours. from the ends to the center of the corner. I wondered how it would work it it pierced the middle and cut out to the edges, but I never tried making a punch shaped that way.
Didn't harden it or anything. I will try to find a picture of it and scan it. I used to keep a scrapbook of projects, but I haven't seen it for a while.