one trick i've seen if you need to make your own custom shafts is to chop the 2 sections you want mating together to the correct lengths. Then put a chamfer on each end & put the 2 bits in the V bit of a length of angle iron and hold in place with g-clamps.
Then slowly build up the weld joining the 2 sections together, rotating it as you go.
Another tip is to join the sections close to one end or the other rather than in the middle as that way you minimise being out of true and introducing vibrations
Then slowly build up the weld joining the 2 sections together, rotating it as you go.
Another tip is to join the sections close to one end or the other rather than in the middle as that way you minimise being out of true and introducing vibrations