Hi, I traded a set of APSCO keytops for a set of chipped ivories on a 'Bond' Packard upright for a music store. I thought it would be appropriate to trade new 0.147" balance rail pins for its 0.089" oblong pins to try out a tool I had in mind for enlarging the mortices, following a query I posted here a few months ago about mortising keys and buttons. My friends from Hubbard Harpsichord showed me the punch they use to mortise keys with a drill press, once the balance rail holes have been drilled into the key plank and rail. It is a punch ground with parallel sides the width of the mortise, and v-notched on the adjacent double tapered sides to form cutting edges with the parallel sides. Two suggestions came up in the thread - Ken Jankura described using a drill bit with a key stick jig mounted in a cross vice or alternately free-handed, and Newton Hunt invented a tool on the spot using parallel X-acto chisels attached to a sized shank, also operated with a drill press. Newton's turned out to be very close to Cesar's tool. Enlarging an existing mortice allows one to use the original sides as a guide. In the case of the 0.089" pins the unbushed mortises measure 0.147". I started with a 1/2" HSS rod and ground a tip with two sets of parallel sides measuring respectively 0.147" (the guide) and 0.205" (the width of the new mortises). I put a 90 degree 'V' (sharp toward the tip) into the 0.205" sections, and notched them to form cutting edges with the flat sides. The narrow sides of the 0.147" section are tapered and notched in case the key mortises are irregular, and these notches enlarge at their intersection with the ends of the 0.205" cutting edges to form additional edges and for clearing waste. So there are 12 cutting edges in total. I used a bench grinder, a Sears rotary tool with assorted grinding and cutting bits, and a couple diamond stones to make this. It took about 20 minutes to enlarge the mortices nicely with the tool mounted in the drill press, the throw stop set just to enlarge the buttons and the table raised to minimize effort. Since the guide automatically positions the tool and key, no jigs or vises really are necessary. Now to figure out how to get the balance rail pins out without damaging them. ;) Clark
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