Originally Posted by
1Jumper10
Your bearing rails probably use M6 screws for mounting. The holes in the rails probably have .5mm of clearance for the screws so you can shift the rail about .25mm up or down. (I'm just guessing here so you should verify before you plan anything). Your machine shop should be able to accurately locate and machine the flat and drill the holes for your rails within those tolerances. Regardless, I would only use 1 shoulder on one rail or the other. So when you mount your rails, clamp the one rail tight to the machined shoulder and fasten it. Then move your carriage down the gantry and use it to align the other rail. If you use 2 shoulders with no slop, then it is absolutely unforgiving of any inaccuracy.
For depth on a .375 tube, .125" is plenty deep, I would go a little shallower, maybe .1"
I was typing while you were replying:
The shoulder the arrow points to looks fine. And like I just explained, I would only use one shoulder there as well and just like you have drawn it.
The shoulder(s) I was talking about originally are the ones on your gantry tube bearing rail pads.