Spindle holder for 1.5kw Chinese spindle.

[m_c]

I'd personally go for bang on, that way you get more even, and better clamping force. The more undersize/oversize you go, the more the collar has to deform to clamp, resulting in a less uniform clamping force on the spindle.

As for the slot, if you get it bang on, then a hacksaw blade cut should be more than enough, and if needed wedge the slot open a bit with a plain screwdriver until you get the spindle in.

[Jonathan]

I'd personally go for bang on, that way you get more even, and better clamping force.

I agree entirely. I generally bore it on my lathe (to get an optimal finish and accurate circle) using my spindle as a gauge. When my spindle only just slides in I stop. Next I machine the slot with a 1mm slitting saw and on one occasion 0.5mm as the 1mm broke. Doesn't make a difference. Next I put my spindle in the two mounts with one at either end with them resting on surface plate. Then use height gauge to measure difference between centre height at each end and put one or both of the mounts in mill and skim the measured amount off so that the spindle will be held precisely parallel to the Z-axis plate.