So I have been doing this for about 3 years now. I know it works, but do so at your own risk. For all of my filters that use steel impeller shafts I measure the diameter of the shaft 3 times with a decent digital caliper. Just to make sure I get a solid measurement. Then I order model plane propeller shafts in the same diameter. I usually get 6-12 12" sticks for about 15 bucks. They are 316 stainless with a tight tolerance and pre polished. I then cut them to length with an angle grinder, round the ends slightly with a bench grinder, and call it a day.