Well I'm dreaming up a new machine and looking at the different rack choices at mcmaster and all..

Anyway new machine will be a 10x5' machine. Current machine is 4x8 with rack drive on the long axis using 14.5 deg gears.. Was thinking about going to 20 for the larger machine. But looking at the gear selection it seems they have less choice far as gear sizes in a given hub size. Thinking I might switch a few gears after the fact to get my speeds right only to be limited far as what I can do.

Probably would be using the 3/4" face with racks. Would be using 2 racks on each side for the long axis, 1 rack on Y and 1 on each Z. I think the 14.5 in that size would hold up and work well given my experience using the 1/2" face width rack on my first machine.

But figured perhaps some one who might be using 20 deg rack might chime in and convince me that 20 is way better (maybe better back lash as well or something else.. then the 14.5)

Rack gears will be driven by servos through 10:1 thomson planetarys..

This will be a suspended gantry design (like my other machine.. except using proper (LARGE) star rails in all directions. Pic of my old machine here: http://users.ameritech.net/watchdogf...ineDetails.htm

Thanks for any