If you're talking about clamps like this he needs to be able to tap the holes too. The threads for the clamps are 1 1/8" to match a metal cutting tap we had. The bigger one is from a wood tap of 1 1/2". The threads were cut on a table saw with a special blade we had made. For grins my dad made a 4" diameter thread with it. I can make the threads for you but can't guarantee the fit as his tap could be different and if I have to make the threads in the jaws too I might as well do the whole thing. Not keen on going into the clamp making business. He would be better off biting the bullet and get a Beall router jig for threads. Threadboxes can be difficult to tune and get right. That's why we went to using the table saw.
Woodchipper they are usually a 60 degree but can be 55 degrees or even to 90 degree V threads. Acme are rare and not in smaller sizes. Big press type things.