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How worn are your half-nuts?
- Thread starter 12bolts
- Start date
- Joined
- May 2, 2014
- Messages
- 217
Just my thoughts on lead screws and half-nuts...
When shopping for a lathe, it is better (in my opinion) to buy a machine that has separate screws for carriage feed and thread cutting.
Single screw lathes get all the wear from turning every time you engage feed. That same screw and half-nuts will be used for threading, which may give poor results since the screw probably has wear in pretty much the same area.
Thread cutting is usually a limited use of the machine, but turning is a huge part of lathe operation. A separate screw and nuts for threading should give many years of good performance.
When shopping for a lathe, it is better (in my opinion) to buy a machine that has separate screws for carriage feed and thread cutting.
Single screw lathes get all the wear from turning every time you engage feed. That same screw and half-nuts will be used for threading, which may give poor results since the screw probably has wear in pretty much the same area.
Thread cutting is usually a limited use of the machine, but turning is a huge part of lathe operation. A separate screw and nuts for threading should give many years of good performance.
The half nut on my 1941 Sheldon was worn so bad that it would not feed to the left with out skiping on t he lead screw.I sand blasted the nut filled the thread with JB weld , greased the lead screw where the thread was best near the tail stock, and clamped them together over nite. It has been working good so far .Not sure how long it will last. However I rarely cut threads or need power feed any way.
- Joined
- Jun 7, 2013
- Messages
- 10,449
I repaired a set of half nuts for a lathe of mine (an older South Bend 10") by setting up the half nuts in the position they occupy when closed, bored them out about 1/8" on a side, facing the ends off a similar amount, then made a new nut with flanges on the ends to fit snugly in the half nuts, split the bushing and secured the halves in the nut casting with a rolpin through each end of the flanges. The threaded portions were beveled along their length to facilitate clearence when open and ease of closing. This is a very good fixif there is sufficient metal in the casting to allow the oversize boring required.
- Joined
- Jun 7, 2013
- Messages
- 10,449
What I did; picture the newly made nut after it had been split, you are looking down on one half of it, at the threads; what i beveled was the corner of each thread on both sides at about 45 degrees so that they slope down towards the middle; doing this allows easier engagement of the half nuts, and they do not have to be opened quite so far to disengage as if they had been left with sharp corners. If you look at most half nuts, you will likely see that this was done at the factory, for the same reasons.
VTY John