I use one with a 3/8 hole to smooth out and size split timber shafts. The next hole down 23/64 is too small to get a shaft through without extra work. You can pound shorter dowels through, but I haven't had any luck with shafts.
I have seen them with two smaller holes drilled 180 apart, intersecting the main hole, to form "teeth". The shafts is rotated and it works like a dowel machine.
Kyle