There is a special knocker to replace the axle nut, kinda like a big, long acorn nut except it's flat on the surface that it hit with the hammer. They didn't use to be very expensive, I bought mine 40 to 50 years ago. But you do have to make sure you hit the knocker square so as to not bend the end of the axle. It's been a long time since I have even seen mine but it's around here somewhere.