Here’s a simple way to make your own expanding mandrel. Take a piece
of mild steel and turn it as shown in the following diagram…
Drill and tap an axial hole a bit deeper than the shoulder, but be
sure to use only a taper tap down to about the centre of the ring.
Cut the two slots with a hacksaw, place the ring up to the shoulder,
and when you tighten the bolt it will expand the mandrel when it
reaches the tapered thread.
I’ve made several - they are easy, quick, and cheap to make, and
work a treat.
Regards, Gary Wooding