This article deals with modifying the take up nut on a RF-30 Mill/Drill in order to reduce both backlash and change in backlash over distance. It assumes the Y leadscrew is parallel to the Y ways within 1/2 thou. How to do that is the subject of a future article.
If you are interested, please see
As an owner of an old Taiwan RF30 this is very pertinent to me. I have yet to delve into the X and Y adjustments. I would like to go through the whole machine because it seems it's gone through a lot of different owners and each person seems to done his own little "experiments" that I've had to go in and fix. Each fix though has made the mill work much better and having so many users like yourself who have published your improvements/fixes have been a true godsend in my quest to understand and maintain this mill.
You may go screaming from the room when you see what I had to do in order to adjust the X and Y leadscrews so they are parallel to their ways. Had to deal with XYZ movement along with roll, pitch, and yaw. Yet the results make it worthwhile. This is the only way to get a small backlash without binding.
Looks like a real winner for removing backlash. Perhaps you can modify the lower screw to be your own version of a NYLOK® TORQ-STRIP® screw by using a Dremel cutoff wheel to cut a thin slot and then filling in with RTV silicone. Looking forward to you next article on the RF-30 Mill/Drill.
Your suggestion of increasing friction on the screw is a good one. I have played with RTV many times and found it does not hold up well around movement. Using a strip of nylon is far more robust. Someone suggested using a Belleville washer between the parts and that would work too. Using split washers would not be good because of the uneven force. I'm wondering if rubber O-rings might provide enough pressure on the parts to lock in the screw. These O-rings only need to provide drag and will not see any leadscrew force.
Paul's nylok torkstrip type bolt would be my choice too. But if I was going to make one I agree with Rick, RTV just won't hold up. But UHMW would, it would just be tricky to do that small and I'd have to make it beforehand because this will take the mill outta commission. O rings in my experience are lousy washers. They are made to be retained in a recess with x amount of compression. Without the recess they squish out and split.
If I was going to do some kind of torkstrip, I think I'd want to do the other bolt too so I could have the approximate same feel to hope to tighten them equally, no?
BTW I've been working my way through your site and looked through the tutorial on pulling the lead screws, but I don't see anything on the kind of lube you used to reassemble. Mine needs that cleaning pretty bad, but a while back I put some Mobil1 on the X screw and it was magic. I know the old Bridgport we had at work had a single point oiler system. What would be wrong with oil instead of grease if you kept track of it?
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