Tool diameter accuracy

[Neale]

I won't bother with a picture. It's too embarrassing... The machine is basically the JGRO design, and there are lots of references to it on the 'net.
I'm using (all from Zapp) a 68V power supply driving 3 M752 drivers, fed by a ZP5A-INT BOB. Motors are all SY60-something 3Nm steppers. Given that they are driving relatively fine-pitch leadscrews (1.25mm) at modest speeds (max rapid is about 900mm/min to avoid whip) with 400microsteps, I don't think that the motors, etc, are being overpowered by the cutting forces. 3mm cutter, 1.8mm DOC, in MDF? FWIW, I also use LinuxCNC, which seems to be a minority choice on this forum, with clock rate within the max suggested by PC latency tests. I do seem to get good repeatability; I can cut several sets of those cable chain components and pieces are cleanly cut (as clean as MDF cuts) with good registration of first and second passes, as far as I can see.
Don't build your CNC router from cold-rolled cow dung...
(Indeed, the Spit looks good so far. One of the projects that I shall get round to one day, and one of the drivers for building the router in the first place, was to cut components for a RC glider. That project's still way down the list, though!)