Well, I found a .281\" reamer, so I drilled all the holes. I did them all in the mill, but I still had issues with the holes wandering on me. What procedure do you guys use to drill these deep holes in the carrier block. This is what I did:
1. Assemble the machined parts, carrier block, front and rear barrel plates with a .374\" pin through the .375\" reamed hole in the center.
2. Zero the carrier block in the indexing head.
3. Drill for the dowel pin, install dowel pin to prevent shifting during machining.
4. center drill, stub drill .265\" diameter with a standard positive rake drill thru the front and rear barrel plates.
5. drill as deep as possible through the stack (about 3\" deep) with a zero rake .265\" diameter drill.
6. Repeat steps 4&5 for all 10 holes.
7. Remove barrel plates, finish drill .265, drill .272, then ream .281 thru each hole.
The carrier block was not removed from the indexing head until all holes were drilled and reamed .281. I still had some wandering of the bit. My plan now was to flip the carrier block, re-zero on the center & on the straightest hole, then use an endmill to open the holes to .375, then open them up to the .420\" dimension.
How do you guys do it? If I had to do it again, I think I would flip it the other way and drill a .405\" or so diameter, then drill thru the assembly with an extended length .265\" drill to minimize the length the small bit has to drill. Then ream .281 thru, then ream the .420 size to the appropriate depth.