Posted by Jim Pollock on October 31, 2009 at 18:11:47:
In Reply to: Re: More Barber #12 hobber questions posted by BillS on October 28, 2009 at 00:21:16:
I did some more work on the hobber today and you are right. The lead screw is worn more toward the center than the ends so I can't remove all the backlash in the screw without recutting the screw to make it the same pitch diameter all the way down. I checked on the nut and mine is not split and there is no way to adjust it that I can see. Maybe my machine was never meant to be able to climb cut.
I have made new nuts for large boring mills and they actually had two nuts in them that were keyed on their o.d. in their bore. You could take out the backlash by adjusting the nuts in towards each other. Then the screw would rub the one side of the thread on one nut and the other side of the thread on the other nut. This was dependant on the pitch diameter of the screw being the same all the down its length. Usually just like my hobber, the screw is worn.