Quote Originally Posted by Jonathan View Post
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.
The Hiwin pdf I downloaded from Zapp about a week ago gives the height from bottom of rail to top of block as: HGH20CA = 30 and HGH15CA as 28, so much of a muchness. Are you figures for a different model or have I cocked up?

Yep, I will also need some milling done in the Z/Y plates.