I made a hand spring fuller and it works well but when i hit it it flattens out the top and dents it were the hammer hits it, what should i do to fix it? should i temper or harden, and also should i temper hammers?

You could weld a small square piece of say 1/4" flat stock to the top of your fuller so you have a striking surface.

Mine does the same thing. Actually after a while it stopped and hasn't gone any farther. I just ground the sharp burs off and it hasn't been a problem. If you want to reduce any further wear, just weld on a piece of flat bar like Flaming S Forge said.

mine does the same thing, too. The original I wore out on some big Stainless, the replacement is made from rebar w/ the texture ground off the work surfaces. This seems to be tougher, but hasn't had the workout of the origional yet.

Thanks guys i was worried after the 5th or so use it was going to were out. so thanks to the advice im going to put it to good use.