Look at the drawing attached. I have 24 of these parts to make (in steel), not to mention several others that have the same situation. Right now I am looking at 3 steps: center drill, thru hole drill, then counterbore. I am trying to figure out the quickest way to do this. First question is can I eliminate the center drill step? These will be clearance holes for a 1/4-28 bolt 1.5 inch deep, so how much could the bit walk? Second question: how would you do this, I do not have an automatic tool changer, it is CNC with quick change tooling though. I can either put a part in the vise and do all operations, or I can do the first operation (center drill or thru drill both holes) then change out part, go through all 24 parts, change tooling to next operation, unclamp, clamp, unclamp, clamp, etc. I would think without an automatic tool changer it would be best to do one operation at a time.
Also, Mcmaster sells combination counterbore/drill in screw sizing, any opinions on these? It looks like the overall length is only 1.75 though, so I doubt they would be any use for this.
Thanks for any input!