Bill Ballard & List - Chucking reamers are intended for machine use (as opposed to hand, though that would not be a sin). One cool thing about them is that their flutes are not equidistantly spaced, although they appear to be evenly spaced at a quick glance. The purpose of this is to reduce harmonic "chatter" of the tool in the work and produce a more perfect surface and more uniform diameter hole. Chucking reamers are designed for very small amounts of stock removal (typically less than 0.010"), essentially a finishing cut on a hole drilled very slightly undersize. Most chucking reamers have a cylindrical shape (no taper), except for a small chamfer on the leading end to help the reamer center in the hole. I can't imagine how you'd use this tool to "start out a brand new balance rail hole". You could use a #27 chucking reamer (0.144") after drilling with a #28 or 9/64 drill (0.140+"). This might be especially useful if working hard maple for a very nice hole. - Tom McNeil, RPT - Vermont Piano Restorations
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