Replacing rear stub axles

I'm converting the swing arms on my 'alf Elf trailer to dry type axles so I can mount motorcycle shocks. I'll chop the rear part of the subframe off and convert it to a beam axle carrier setup.
Anyway, I've beaten the old stub axle out of the arm. It actually came out easier than I expected. Now I need to put the new dry type axles in, but I'm not sure what the best way is to get them seated all the way in. Someone once told me to heat up one part and freeze the other part so the metal would shrink/expand and they would slip right in, but I'm afraid I failed my molecular science classes. Do I heat up the arms and freeze the axles, or is it the other way around?
Or is there a better/easier way to do it?

I helped my son (a mechanic) to change the bearings on a motor some time ago. I popped the stub axle in the kitchen oven when the wife wasn't looking and the bearing in the freezer for about 10 mins, The bearing took a little persuasion in the vice (you could use a lump hammer and a piece of wood, if you haven't a vice big enough but make sure it goes in square!)

Let know how you get on and good luck!

Stub axle in the freezer, blow torch/oven on the arm.

Make sure you drive it in square and don't damage the threads on the end.

wow wow wow, none of the above is correct, the correct way to do it, is to use a press, mandrel and die, a little bit of oils and a lot od patience, a local garage should be able to perform this for you for a couple of quid, indeed at my garage we do bearing fitting for other people, diy chaps just for tea money,