Clearance between mortising chisel and bit. I'm not quite sure of this

[Don Stephan]

I keep a dime, penny, nickel, and maybe a quarter with the mortising machine tools and use one, depending on the size of the hole being made. Don't know if I noted which to use with each chisel set size.

[William Chain]

Old school is to put a dime under the shoulder of the chisel, slide the bit up until it touches, tighten the chuck for the bit, take the dime out, and slide the chisel all the way home.

I do this idea but with a rare earth magnet about the thickness of a quarter. It holds all the pieces in place, I get the bit chucked and tight, then raise the chisel collar up by removing the magnet. This seems to work nicely each time. And make sure those chisels are honed.