How to choose a lead scew

[Smiler]

Hi GTJim

Hi, just hoping to draw on your experience.
I have just decided to start my design for a router. I want a working area of approx 1000mm x 1000mm, and will mainly be used for wood but I can see the need for some aluminium work.

Size is similar to mine.

I am going to base the final design of the router around components I can readily get, but I am having trouble deciding on the size of lead screws I need. I was initially thinking about 16m x 5mm pitch but I am unsure whether I should increase this to 20mm or 24mm.

I have a 25mm ballscrew on my X (your Y). I was going to use a 20mm but Zapp were out of stock. 25mm was probably overkill but I'm not complaining.

Z axis is a 16mmx 5 ballscrew and works brilliantly throwing around a Makita 3612c.

Steppers are 3Nm from Zapp's excellent Driver Kit 1.

Also I was thinking about placing the X axis lead screw central under the moving gantry and using a ball screw, but would two trapezoidal lead screws running either side of the gantry work as well and be of a similar cost?
I understand that having two ball screws on the X axis would mean two motors.
Any advice would be welcome.

If you use a belt drive from your centrally fixed motor, you only need one and you won't get the problem of racking should one motor stall. Might be a much cheaper option to two motors/drivers/slaving headaches. Go for ballscrews if you can afford it, really.

Cheaper alternative (but just as good IMO) is what I chose and that is a rack and pinion drive.

Regards, Jeff.
I get rapids of up to 4m/min stable but turned it down to 3.5m/min.