[flisher]

Hi I'm John a new boy so go easy on me. I have been interested in engineering for years and have a Harrison 600 tool room lathe and a Bridgeport series one milling machine. I wish to join you CNCers by converting my mill, and have some questions I hope someone will be able to answer, they are:

1) What diameter ball screws do I need and can I use the existing nut holder?

2) What backlash if any?

3) What pitch?

4) What size direct drive motors for three axis, steppers?

5) An indication of the speed as well. (RPM)

That's it folks I have had my two pennorth.
Happy milling.

[Cartierusm]

Welcome and good luck.

1. Most use Bridgeport Replacemnet ball screw kits from Hiwin, NSK, Roton, Nook or Rockwell. They are 1 1/4" OD.

2. You want to make sure to get a zero backlash Ball nut.

3. Most use the stock pitch .2", so every turn of the screw moves .2" or 5 TPI.

4. I'm still working on this, if using servos you'll need to reduce to 2:1, but I'm going to be using 1200 oz/in. Steppers direct drive and hope that this will work without losing steps, but then again I have a brand New DRO to test installed so I can check the accuracy without hooking any dial indicators up.

5. I'm not sure what you mean by RPM, do you mean how fast the axis moves or the rpm of the spindle motor? If you're talking about the axis movement it all depends on what size motor, how big a power supply, gearing and all that. Basically you need to know how fast , inches per minute, you want to achieve and then go from there. If you go to Gecko drives website and click on FAQ there is a formula for figuring out what size motor you need to achieve the IPM you want to get. I suggest you read the whole FAQ it's very well written and quite informative.