Sure, you should be able to do this. Be warned that the dies are hardened, and so even carbide tools may find it very hard to cut. You may want to anneal the dies first, cur to size and then harden again. A fair amount of work to do it right. If you were just going to open them up a few thousandths, you could grind them in the hardened state.
I got around to inventorying the punches and dies that came with my '80-ish ironworker. It looks like this unit punched a lot of 3/8" and 1/2" holes as there are a lot of dies in those sizes that are very beat up.
Logic says if I have a 3/8" die that is all beat up around the hole, that I should be able to machine it larger, to make a usable e.g. 1/2" die. Is this possible? I see that a die is about 11 bucks, so it isn't worth spending a ton of time on. It's just that I seem to have about 10 unusable dies, and I'd like to use them.
You can grind or turn them. Most ironworker tooling is not highly hardened. Use carbide or ceramic inserts. I usually just use carbide on ironworker or Roper Whitney tooling. Be sure to leave enough land on the die for future sharpening. This is a good time to set clearances for different thicknesses of metal. You can take that 3/8 die to .525 or so for 1/8 thick or to .550 for 1/4 thick with a 1/2 punch..
Be sure to stone off any grinding burrs before punching. They will dull a freshly sharpened punch or die very quick.
I would leave more than a 1/16 land on an ironworker die. You don't have the precise stroke control like with a punch press. An ironworker punch usually pushes into the die a good distance as the material fractures. Take a look at the land in the other dies you have. It doesn't hurt to have and 1/8 land or even more. Ironworker tooling tends to take a beating. Leave plenty of life for resharpening. As for the relief taper beyond the land, the 2 degrees that Robin suggested will be fine.
I turn 58-60Rc hardened punches and dies on import 12 and 14" machines quite often. A ceramic insert run dry like the NTK ZC-4 cuts them like butter. Chip comes off glowing red. All the heat goes into the chip. The part stays cool to the touch. That ironworker tooling will be softer. Carbide should do it.
That's right Robin. 20% total clearance for MS on an ironworker is what should be used. It will leave nice holes, require less stripping force, and make the tooling last longer. Grant had mentioned opening the 3/8 die up to a 1/2 die. I would use a .395 to .400 die for punching a 3/8 hole in 1/8 thick MS. Different materials and different operations may require different clearances. I generally run 20% total clearance on a daily basis with MS.
To explain this a little further. For punching a 1" hole in an item, I will use a 1" punch. The clearance is on the die. To accommodate the different thicknesses of material, I have probably
10 different size dies at least, that could be used with the 1 punch. Now I want to punch out a 1" circle blank or slug. I will use a 1" die and the clearance will be on the punch. And again, to accommodate the different material thicknesses, I have 10 different diameter punches.
As you can see, the number of punches and dies needed to do different size holes and blanks in any thickness of material can be staggering. I have never added up the amount of punches and dies I have. The amount is well over a thousand and I make new ones every chance I get. This is for precision stamping and being able to do just about any size. On an ironworker, the clearance doesn't really need to be exact for punching holes. You could get by with the same die for a couple of different fairly close material thicknesses. It will just make a difference on the quality of the hole.