just received an acme screw and delrin nut.. Question about tightness

[blau_schuh]

The delrin nut seems to turn pretty easily on the screw until maybe 5 turns in, where it becomes pretty hard to crank by hand.

How tight should it be?
Should I be able to turn it by hand without putting much effort?

Thanks

[Geof]

Originally Posted by blau_schuh The delrin nut seems to turn pretty easily on the screw until maybe 5 turns in, where it becomes pretty hard to crank by hand. How tight should it be? Should I be able to turn it by hand without putting much effort? Thanks

If the No indicates Norway my (not serious) suggestion is wait for summer; Delrin has a large coefficient of thermal expansion.

[tager_rot]

As a rule of thumb that I adopted when building my cnc.... If I could not turn the lead screw with my thumb, index and middle finger (on my 5/16" nut and while it was fully assembled with the motor attached) then I would fine tune that axis more. I found that if I couln't trun it that way my 269 oz. stepper that was attached "in-line" with the lead screw would stall. At least that is what I experienced.


Justin!!!

[planekrazie]

Small question about Geofs coment. Now I understand why my leadnut is stalling out my steppers in the cold mornings. I have to heat up my building for 1 hr to jog my router. Could this be the problem. Oh yea I am using UHMW lead nuts. ( homemade)
Steve

Originally Posted by Geof If the No indicates Norway my (not serious) suggestion is wait for summer; Delrin has a large coefficient of thermal expansion.

[blau_schuh]

Originally Posted by tager_rot As a rule of thumb that I adopted when building my cnc.... If I could not turn the lead screw with my thumb, index and middle finger (on my 5/16" nut and while it was fully assembled with the motor attached) then I would fine tune that axis more. I found that if I couln't trun it that way my 269 oz. stepper that was attached "in-line" with the lead screw would stall. At least that is what I experienced. Justin!!!

Hmm, I just got a replacement delrin nut from the seller. same thing. REALLY TIGHT! I basically need to grab the delrin nut as if I'm gribbing an orange and crank at it. at least there is no backlash

what do you mean by "fine tune"?

[blau_schuh]

Originally Posted by planekrazie Small question about Geofs coment. Now I understand why my leadnut is stalling out my steppers in the cold mornings. I have to heat up my building for 1 hr to jog my router. Could this be the problem. Oh yea I am using UHMW lead nuts. ( homemade) Steve

whats UHMW?

[mxtras]

UHMW = Ultra High Molecular Weight Polyethylene - "poor man's teflon". Cruise around on www.mscdirect.com - they have UHMW, Acetal, HDPE - all kinds of plastics and they sell small quantities.

EDIT - Try www.mcmaster.com instead - they have a much better selection for raw materials.

EDIT - Or try this site - it's a bit slow, but there is a large variety of plastics - www.professionalplastics.com

Scott

[planekrazie]

Now I see why its a poor mans teflon. It liks to freeze up in cold weather causing my steppers to stall. What to do, What to do. How bout rack and pinion?