Many (woodworking) shapers are available with interchangeable spindles
so that cutters with different size bores can be used.  This Italian
make (Griggio) was acquired at auction with only a collet chuck.  Very
useful but at least one regular spindle was needed to take my other cutters.
The spindle taper is MT #5, the spindle itself is 1-1/8" dia x 5" under
the nut.  Turned close on SB 10K, finish ground on Cincinnati #2 T & C
grinder.