I see guys doing this without any jig. The guys at Dutchmen commented that many of the wrecker diffs are bent. You cannot detect it without a jig. I suspect mine was in a rollover causing both tubes to bend. I'm very glad I made the jig.
Anyone doing this can contact me to borrow the bushings. The pipe is just black pipe from the hardware store. I did use a long level to pick one that was straight. Some were off a bit.
It is not rigid enough to be a true jig. Rather it is an alignment checking tool. The final welding will be done without the end bushings in place, with frequent checks as the welds are completed. Being so close to the end, as long as short opposing welds are done I do not anticipate a problem.
Some technical info on heat straightening here in the second part.
http://www.repairengineering.com/shaft-straightening.html
