[SpeedyDad]

Pardon my ignorance but what is the difference between 1 start and 2 start anti-backlash nuts and which do we need for this machine?

[JavaCnC]

what is the difference between 1 start and 2 start anti-backlash nuts and which do we need for this machine?

It has to do with how far the nut will travel linearly per a revolution. 1 starts don't travel as far as two starts per a revolution of the lead screw . Really what you need is to match what you buy for a acme lead screw. If you get a 1 start lead screw then you need a 1 start nut. 2 or multiple start lead screws will give you faster rapids. But from what i have read in here I believe the plans call for a single start. Although it could be switched out since the travel is controlled by the software.

[groswald]

The plans call for 1-start, but either are fine. I use a 3/8-10 2 start on my Momus and it works fine. I happened to have it in my junk box.

Randy

[momus_cnc]

Yes, the plans call for 1-start leadscrew and matching anti-backlash nut. However, depending on a few other factors, a multi-start screw (2-start or even 4-start) might be a better match match for the machine.

With the single-start screw, the Z axis has far slower motion than the X and Y, and this can have an impact beyond just rapid moves/jogging. If you are milling parts with a lot of Z movement, like 3d parts with lots of highly contoured surfaces, it will slow the whole job down while the X and Y wait for the Z. Especially if you are taking light finish passes off of those surfaces that could use high feed rates. But even this is a non-issue if you are running an electronics setup that allows you to spin the Z motor fast enough. And if your intention is to primarily mill those type of parts, then you should really invest in the better electronics right from the start, regardless of leadscrew pitch.

So in short, the single-start is a good general solution that will work perfectly for most people's needs, plus it is the easiest and cheapest to source. But depending on a few other factors (electronics and type of parts you are making) you could see slightly better performance with a multi-start screw.

-Bob

[ger21]

.........you could see slightly better performance with a multi-start screw.

From my experience, you should see a 3-5 times performance increase from multistart screws, provided you have enough power.

My machine is 30"x45", powered by a Xylotex and 250oz steppers. My Z axis uses 1/2-10 single start, and is limited to 55ipm.
My Y axis uses 1/2-8 2 start, and can cut at 190ipm.

[SpeedyDad]

Thanks for all the replies. For what I'll be milling, sounds like single start will be sufficient.