Originally Posted by
Geof
With this design when the nut is being driven in one direction the force is acting directly through the body of the nut but in the opposite direction the force is being transmitted through the #10-32 SHCS. Only half of each screw head is in contact with the inner adjustable nut so there is only a very small area of contact. This is the location where deformation of the soft nut material will occur allowing the inner piece to move and introduce backlash. The deformation is almost certain to be accentuated with stepper drive because each step will produce a hammering effect on this small area.
If I make the nut out of Titanium, and use Inconel screws, then you will be able to put the enormas force on the 1/2-10 Acme thread you are refferring to! But because this desaign is for the DIY home built router which according to my polls, is being used for light cuts in aluminum, plastics, foam, and wood, I do not think the bronze will wear as excessivily as you described!
Also, because 50% of the nut is solid, the most it could move is the total sum of the origonal backlash! Usually .003-.007" This entire problem could be resolved by including a threaded ring which would screw into the body of the nut, giving 360 deg. of contact, But I still do not see the necessity!
Eric
www.widgitmaster.com
It's not what you take away, it's what you are left with that counts!