What's the trick to a good weld on a band saw welder. I can't seem to weld them together. I get gaps in the middle of the weld. Please help!

Your welds are overheating and the metal is dropping out.

I assume that the moving jaw must hit a switch after the weld zone is hot enough to relax and allow the upset to occur, and the jaw to slide.

The technique may vary according to the particulars of the welder. What I would try is to preset the 'blade width' setting to that of a slightly smaller blade than I am actually welding. What this does is sets less distance for the moving jaw to travel before the current is cut off. So in effect, this is less heat time because I don't think the applied current is different from weld to weld.

I agree with Hu with one addition... before welding, make certain that the blade ends are square to each other. To do this, put a half-twist on the blade before grinding (one side has teeth, the other is the back). Even though the ends might not be perfectly square to the length, they will match perfectly when welding.

Bud

anneal it after welding !!!

i have a Ideal make welder BAS 25.
can someone guide about correct method of cutting the ends before welding so that
exact teeth profile is maintained after the weld.
do we have to take care of TPI achieved after the welding.
regards