I meant to add a little more on motor sizes.
For the cross screw I wanted a motor that wasn't too big so it wouldn't be too much in the way for manual use, I made a motor bracket that clamps on the cross screw bearing housing just behind the handle. The stock handle is still in the same place but the graduated dial got replaced by a timing belt pulley for the motor drive.
However I put graduated marks on this pulley so that for manual work I still have it as a reference.
The bracket is slotted for the motor so it only takes about 20 seconds to slack the drive belt so I can use the cross slide manually.
I used the larger 400 oz-in size 23 motor that is sold on Geckodrive.com for this, its a nice combination of pretty good power in a limited size. I geared it at 2:1.
For the Z I used a 1300 oz-in size 34 motor that AutomationDirect.com sells, their STP-MTRH-34127. I liked this motor as it has a low inductance for its size, I wanted this so I could run both motors on a 48 volt supply.
Both these motors will work well with GeckoDrive stepper drivers, I'm using the G201x ones.
I need to make some steel parts that need heavy drilling so that's why I went with a pretty strong motor on the Z (lead) screw, fortunately I don't need much power on the cross-slide so the smaller motor works fine.
The Z drive uses the threading nuts on the lead screw, which means its also very quick to release those nuts so I can use feed handle on the carriage for manual work.
I used needle bearing based thrust washers (McMaster.com) to get rid of all the end to end slop in the leadscrew itself and the threading nuts on machine were never used much so the backlash on Z is actually not too bad even just with this stock lead screw, its fine for the work I need to do.
Paul T.
www.springtest.com