Now that I have a milling machine I can improve my milling machine.

From the start I've called this component "the bearing-holder". I couldn't think of a better name. It's a sort of lever-arm with a roller on the end that keeps two sliding channel sections together. There is one on each axis.

The first picture below compares the old and the new. The old one is pretty bad. (It was the first and worst, I think.) It "features" a crude, curved slot that has been hand-cut in the least effective of the two positions. The new one is slightly wider, slightly longer and the curved slot is pretty good.

Like much of this machine, this component is made from MDF (12mm thick in this case) but I don't think I'd use MDF for anything smaller. It just gets a little bit crumbly at that scale.

The following photo shows the other side where the head of the screw that goes through the bearing needs to be recessed.

And finally, here one in place on the underside of the Y-Platform. The 20mm aluminium channel section that I'm using determines the gap that this component has to fit into. There is not much left after 12mm of MDF, a washer and a nyloc nut.