[rotorwrench]

From the looks of the illustration for the McMaster Carr punches, they are a different shape. The Model A "D" nuts only have a small area of flat for the diameter of the hole. I have always done them the hard way. I compass the circle on the known center line then straight edge the flat for size in the original location. I use a single flute step drill to enlarge the starter hole then grind & file the aperture to fit the D-nut going in. I go for as tight a fit as I can get prior to setting the D-nut.

To fabricate the die it takes to punch an aperture of that shape would take a special broach to get it right. Not impossible but the equipment to do it is expensive. The die and the punch have to have hardened edges to use them on thick sheet metal such as is common to the model A in the places where they were used. The aperture shape is common to key lock cylinders but they are generally a larger size.