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- Feb 8, 2014
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- 11,144
In those sizes I would use a combination of drilling, boring , and reaming. I have had a lot of experience in ''boring'' 11/16 holes through about a foot of 1.5 inch Inconel shaft, and I did this on a Craftsman Commercial 12x36 lathe, my first lathe back about 1971. I made 30 or 40 of these shafts. They had to be on size and straight. First paying job I ever did with my new lathe 
, and it paid for the lathe several times over. There were also several features and steps on the OD of those shafts.
Anyway.......
First I center drilled, then went in with a 1/4 inch bit a couple of inches. Then in with a 5/8 bit to the bottom of the 1/4 hole. Now I have clearance for the boring bar and bore to 0.671 (43/64) , now I have a straight ''drill guide'' built into the part. Now through drill with the 43/64 bit, starting straight and with a properly ground bit, the hole is straight. Finish by reaming with a with the 11/16 reamer.
This same process will work for what you want to do.
, and it paid for the lathe several times over. There were also several features and steps on the OD of those shafts.Anyway.......
First I center drilled, then went in with a 1/4 inch bit a couple of inches. Then in with a 5/8 bit to the bottom of the 1/4 hole. Now I have clearance for the boring bar and bore to 0.671 (43/64) , now I have a straight ''drill guide'' built into the part. Now through drill with the 43/64 bit, starting straight and with a properly ground bit, the hole is straight. Finish by reaming with a with the 11/16 reamer.
This same process will work for what you want to do.