You've got the mortising machine, the chisel and bit sets and you've read that the bit clearance from the end of the chisel should be 1/32 to 1/16 of an inch right? But where do you measure the gap? Guess wrong and you either blow a hole out the bottom of the mortise OR you turn on the machine and get a hell of a racket as the bit grinds against the inside end of the chisel and burns itself AND the chisel into two pieces of scrap steel.
Well here's an easy to remember AND actually do method. You have the Fisch Rep to thank for this little tip.
For those using the metric system, compliments of Jack Novak of rec.woodworking
Dime = 1.35 mm
Nickel = 1.95 mm
Quarter = 1.75 mm
(Source: http://www.ecoinprices.com/us-coin-specs.htm )
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Jack Novak
Buffalo, NY - USA