Low cost 0 backlash transmission - Ball bearing + trapezoidal screw

[Jonathan]

If say you were using a bronze nut "You Don't Use Brass" that was 12mm long that would have a contact area on the thread of (12x3.142)x12 of 452mm approx, using a bearing this way would have a contact area of approx 20mml

True, you're not going to be able to put anywhere near as much force on it - and the pressure is much greater due to the tiny contact area. Probably only a couple of mm, not 20, since it's only contacting at two lines (in theory). Could improve this with more bearings.

The fact that this idea is not commercially available says it all really.

Yes it does. Except one thing - the sort of machines we're making are generally not used for heavy cutting (like commercial machines). I think this method excels when you're only cutting woods/plastics so the forces are low. ACME rod would certainly be better, but I just used stainless rod as I know that eventually I will probably buy a ballscrew.

It could be good for a PCB machine where low backlash is going to help with accuracy and the cutting forces are tiny.