Sherline Repair

I doubt most of you care about this, but I am putting it as a resource for others who might need help.

I followed instructions at http://sherline.com/5011uinst.htm for installing new Y axis backlash nut  Problem is that the nut does not go on the leadscrew easily.  It requires grabbing it with channel locks to turn on to lead screw, which chews up the brass barrel of the nut, preventing it from sliding into the recess where it goes.  Trying to turn the lead screw back into the X-axis carrier base, requires turning the nut at base of motor mount, but that rapidly unscrews from the base because it is threaded the opposite direction of the lead screw.   Solution, Loc-Tite to prevent turning.

I ordered two more backlash nuts and a new lead screw (which was $15.50--much cheaper than I expected).  Why the new lead screw?  Because I suspected the problem wasw damage to the lead screw, and Sherline warned me that they thread their lead screws about .100" oversize, and just using a LH 1/4"-20 die would cause backlash problems.

The new backlash nut turned onto the new lead screw without difficulty, but the nut would not turn into the  hole, so I assumed the problem was debris in the hole and I removed the lead screw.  But removing the nut was harder than going on, and after verifying the nut would slide into the hole just fine by itself, it would not go easily back onto the lead screw.  It looks like the place where the set screw through the table hits the lead screw is the problem.  (Don't screw it down so tightly next time.)  I used a file and sandpaper on that section without success.

Because the problem was apparently damaged threads on the Y lead screw(s), and Sherline makes them .100" oversize, I used an adjustable die open as far as possible.  As I had hoped, the die met no resistance except in the sections where backlash nuts had stuck. As a result, I can now turn the backlash nuts down the lead screw(s) by hand without difficulty.  So I reassembled, and even though the star washer is grabbing the projections on the backlash nut, the backlash nut still reverses out of the hole, failing to pull the table back on the Y axis.  I tried stacking two star washers to increase the range of spaces to grab the backlash nut, without success.  I am rapidly developing gobs of experience on repair of this mill, but I still don't have a working CNC mill.

Some pictures.