All axes on the machine are driven by ACME threaded lead screws. One end is attached to a NEMA23 stepper motor via a coupling. The other end is supported by a 3/8″ double shielded ball bearing in a mounting block with thread clamps on each side, to further reduce backlash.

Heating up the bearing blocks on the Fab@Home heated build base

The ball bearings and the bearing mount blocks have a very slight interference fit. So I thought “why not heat up the blocks on the Fab@Home heated build base?” They were heated to around 100°C in order the expand them. The bearings were placed in the freezer in order to shrink them a little. This made it slightly easier to get the bearings to fit into place. I ended up using an Arbor Press to get the bearings flush into the block. When using the press I made to sure to exert the force on the outer casing of the bearing, in order to keep the load from being directly placed onto the ball bearings themselves.

Ball bearings press fit into their respective mounting blocks, next to the ACME threaded rod

These blocks will be fastened into position. From the above image, the top block will attach into the base table while the other two smaller blocks will either attach to the Y or Z axes (they are basically the same design). I did not turn down the ends of the ACME threaded rod as is common with linear motion stages. This is because I purchased couplers and thread clamps that are threaded to my ACME size. So this saves a little bit of time by avoiding another part that needs to be machined, also having threaded clamps and couplers will hold my lead screws in place better.