Drill a hole about half the diameter of the axle in a metal block, then drill a larger conical hole on the same center. If you can drill, or machine, the cone to match the end of the axle, so much the better.
The idea is that the axle point will go in the center hole, so it won't be taking the pressure. Ideally, only the point touches the truck frame, so if the rest of the axle end is roughed up, it shouldn't matter.
If the metal is a little softer than the axle, it should "flow" to match the axle cone. If it flows too much, you might have to clean out the center hole. If you can match the taper to start, you can use a harder metal for the block, and it shouldn't damage the axle at all.
If you want to use the vise, make two of these, align them carefully, and you shouldn't have any problems.
This worked like a charm. Only needed one, because the wheel takes all the force on the other side (just need a clearance hole in a wood block for the axle). As a bonus, the same gismo worked nicely in the NWSL puller after I pushed the wheel on too far!
That said, Pete's idea (just use a Kato geared wheelset), is beautifully simple, and if I ever need more of these I may go that route.
