Step 2: Mounting the Drill, Bearings and Shafts
We use the angle brackets to hold the bearing flange mounts in place. The great thing about these flange mounts is that the bearing can swivel (ball joint style) inside 10-15 degrees before you tighten them down. So we get everything roughly in place, make sure the shafts can spin, and then tighten the flange mounts down.
We use a 1/4" shaft in the drill chuck and a 1/2" shaft in the bearings. A 1/4" shaft was used because the drill chuck only accommodates 3/8" shafts.
We first tried just wrapping tape around the two shafts to make a couple that matched the ghettoness of the rest of the setup, but that failed horribly after only a few runs. The "spider" coupling from mcmaster provides a backlash free way to connect two different sized shafts that have some angle and axial misalignment. You buy the end pieces and the middle piece separately to fit your shaft sizes... less than $10 overall.
Since there are relatively no loads in this system compared to the 1000 lb capability of these bearings, the solder spool is only supported by a single bearing. One thing we were worried about was the Feeder spool continuing to spin after the Target spool stopped. As it happens, there's just enough friction in the bearing to stop the Feeder spool, but not so much that the solder wire breaks.