Linear rail question

[JAZZCNC]

Your thinking correctly but do your calcs with the longest drill your likely to use rather than cutting tool. Also remember Clamping etc because you'll need to retract above it.

[Boyan Silyavski]

I wouldn't DIY a cnc with less than 100mm real Z travel to sacrificial layer. Or even better - no less than 150mm Z travel to bed with tool mounted. That means by moving the spindle up and down an additional height could be gained, so no less than 180-200mm from lowest gantry or Z part when Z is raised to table bed/ the clearance/.

Doesn't matter if would work with flat sheets or not. Additional sacrificial layers, vices, fixtures, holders, clamps, part height... that easily eats from your travel. I have a small machine with 100mm travel, have made with 200mm and now my big one is with 300mm clearance. But that's my design point of view of course. So to resume- 150mm Z travel and 200mm clearance will be a big ++++++++++