Reply To: Bushing with Drill ?

[david pierce]

Marc,
Bob is correct about the drill drifting. I spent several years in a tool and die shop and 22 years in a general machine shop. I know from experience that the only way to correctly deal with a hole is to first drill it undersize then bring it up almost to size with a single llip cutter and finally size it with a reamer. If extreme precision is required the hole can be reamed slightly undersize and lapped to the final size. The single lip cutter can be a boreing bar used on a lathe or a boreing bar used in a boreing head with a verticle spindle milling machine. If there is only a small amount of metal to be removed the broach will work fine. If a larger hole or a new hole is required the plate to receive the hole can be centered and fixed in a face plate and drilled bored and reamed. If a verticle spindle machine with X-Y movements is available the operation is a little easier.
David Pierce