I'm in the process of completing some grips for my 1911. Everything is going very good and has been easy so far, regarding getting the proper shape. I think the hard thing will be to perfectly align the grip screw holes (I advise using a good drill press) and getting the exact size and type of bits for the holes. Two bits will be required; one for the bushing and one for the screw head. I have the sizes at home and a place you can order them from for about $13 each. Not cheap, but if you are going to make some more it's well worth the money. I'm presently out of town but will be back Friday late and will be glad to forward that information to you this weekend.
Ok I found the info I had in my other computer. This is a copy and paste from a post in another forum:
The small diameter is 15/64"
The countersink for the grip screw and the bushing 'flange' on the bottom side of the grip is 9/32". Odd sizes - not easy to find.
I tried and tried practicing on 10-15 sets of grips to get the countersinks perfectly centered on the hole. Even clamping the grip down, drilling the 15/64" hole, then changing bits to the 9/32" for the countersink produced slightly off centered countersinks.
The only good way to drill the hole and countersink is to use a step drill. I had several made at Bits and Bores.com: