DIY Build of Aluminium CNC Wood Router without Workshop & Tools

[Jonathan]

Looks to me like those mounts are milled down to about 3mm? Have you noticed you're missing a bolt in pic-1... or is that one an optional extra... Lol

Yes something like that... you don't need much thickness if there's plenty of material around the motor mount surface to stop it bending. I missed two screws in that picture as it was just a test fit.

I've drawn my pics with 20mm rails because I had already created them as components under Sketchup, but am seeing more and more comments stating that 15mm is plenty good and that would save some dosh, and might bring Z 2mm nearer to Y.

The drawings are available from the Hiwin website by the way...
You can also get Z closer to Y by milling pockets in the Z-plates for the rails and blocks. That's required anyway if the plate isn't nice and flat...

But, I am a wee bit worried about aligning 15mm rails on this particular profile as the slot itself is 10mm wide and then there is a wee surface rebate on each side of the slot, that looks to be about 1mm, which makes a total gap of 12mm resulting in the rail only being supported by 1.5mm on each side! So am thinking that 20mm would better... supported by 4mm on each side?

Ahh didn't notice that. With either size rail I would prefer to see them mounted on a strip of aluminium and have that bolted to the aluminium extrusion to spread the load. Hiwin 20mm linear guides are 36mm tall and the 15mm variety are 24mm tall, so if you mount the 15mm rails on a 12mm thick strip the rest of the drawing stays the same. In addition this maintains a good spacing between the 4 blocks which is necessary for good rigidity.