What size clamping holes ?

[dudz]

Great thanks Jonathon.

I have drilled the holes 10mm deep. hope this is enough.

I know when I used to build motorcycles 20 years ago, it was unadvisable to put stainless bolts into Alu unless you coated the threads in copperslip first, as over time the stainless would weld itself to the Alu. So I guess you all use mild steel bolts to mount the rail bearings to the table ?

[JAZZCNC]

Great thanks Jonathon.

I have drilled the holes 10mm deep. hope this is enough.

You'd be better drilling the thru holes then they don't fill with swarf or chips. If you can't do that then think about removable plugs or set screws.