Ken,

There are Forstner-pattern bits  with bitstock shanks to fit into a brace. ( I
found my set,  in their original factory wrappers, at the Stormville NY Flea
Market about 30 years ago.  )

Roy Underhill shows a bitstock-shank Forstner as a way to excavate the recess in
a wooden box to hold a whetstone.

Several makers currently offer Forstners with hexagon shanks, which most brace
chucks will grip.

Alternative:  Start the hole with a hex-shank spade bit. Once the hole is
established, continue boring with the same size spade bit with the center spur
ground wholly or partly off.

Another alternative would be to convert a Russell Jennings pattern bit into a
sort of “blind footed” bit without a center lead screw and reduced spurs,  again
to be used in a hole established with a normal bit.

[Yes, I do realize that that’s not exactly the definition of a blind-footed bit,
which is an open helix with only one cutting edge.]

A rare Cook’s pattern bit would be ideal for this, but don’t let any collectors
catch ya butchering a Cook’s, as they are quite rare.

John Ruth
Who sees far too many auger bits that have been ruined by ignorant sharpening.