http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=003&sspagename=STRK%3AMEWN%3AIT&viewitem=&item=130058213100&rd=1&rd=1

Clik link (hope it works ) I plan to use these stepper motors to power my bridgeport look alike
this is a conversion from manual to CNC
your thoughts if you please


Andrew Bishop UK

I had 916oz/in with 2:1 reduction and there was way more torque than a Bridgeport could use, so you could run them 1:1 and have more than enough torque. Just depends on what drives etc you are going to use and what resolution you want to end up with as to whether reduction would be preferred.
Hood

Does it have ball screws? I would say they are not nearly big enough.
You should go servo as then are much better when moving a lot of mass. Steppers aren't that great.

The motors are also too low a current for that size. They would be super slow !

Each time you double the lenght of the motor, the required current should double for similar performance (speed/torque). Or else they are putting twice as much wire of the same guage .
4 AMPS for a motor that length is very low.

Andrew, I don't want to rain on your parade, but I have come to the conclusion that a manual Bridgeport converted to cnc is neither fish nor fowl, and isn't particularly good as a manual machine (after conversion) or a cnc. Get yourself a broken Bridgeport MDI or Interact or Boss machine (which go for peanuts when the controllers die). The iron is very solid and will come complete with (preferably) matched servo motors (or steppers in the case of the BOSS ones) - and also already fitted ball screws. Do your conversion on such a machine and you end up with the best of both worlds rather than the worst of each.

thanks Andrew in truth its not a bridgeport but a Clausing Kondia just easy to discribe as a bridgeport they actully do a cnc version of the machine I have
so that was my reason (not the best excuse ) I agree with your sugestion but have now gone to far with the collectinon of parts.
the feed screws were worn on my machine and needed replacing and ball screws were an ideal replacment Ive had the knee reground (found out the ways on this machine are induction hardend )
when the second workshop goes up I will proberly look for interact but I will stick with this project/stress reliever in the meantime

Thanks Andrew