I’ve not mucked around with these, I guess it would depend how it is attached to the shaft.
If it’s a plain cylindrical shaft it might be less effort to mount the assembly in a three jaw chuck, face it off, centre drill and then drill out the remainder. If it’s tapered then you’d need to form a tool and use the sliding carriage on an angle to achieve the same outcome.
I do things like this when I want to preserve the hardening or finish.
Another method, if you still have a decent stub of shaft left, is to freeze the whole thing onto a mounting plate for the press and encase the shaft stub in a block of ice also freeze a mandrel slightly undersize. Doing all this in a deep freeze helps. Next day I mount it in the press and, using the mandrel with the whole thing under pressure, heat the outside of the external part with a torch.
The ice blob and mandrel act as a heat sink and the shaft stays cold while the external part expands with heat and the two parts more easily separate.
Another method is to stretch the external circumference using weld shrinkage. I warm up the whole assembly first, get the whole thing red hot if I can without damaging the bit I want to preserve. Then I weld a great hunk of junk of some description with a hole through it that has thermal mass much greater than the part to it using a series of big chunky welds, leaving gaps between.
As these welds and the part cool they shrink and pull the external part back. The gaps ensure the part doesn’t crack. The inner shaft will be free to shrink back to its normal size and should be much easier to remove.
You can achieve similar effects running thick beads longitudinally down a part with gaps between the beads. Grinding the beads off and giving it a spin in the lathe returns the part to normal dimensions.
These are methods I’ve used to fix machinery, tractors and implements. Sometimes spares are well outside the budget and the thing needs to be fixed asap no time to wait for a part.
