Help with Improvements to the Mini-Lathe Half Nut Mechanism?

Whilst adding a plastic chip guard behind my SC3 mini lathe apron I decided to strip and improve the half nut mechanism. In the case my 'Super C3' (SC3)
it's more a case of a 'half of a nut' mechanism in fact as only the lower half of the usual pair of half-nuts is present because the new leadscrew guard doesn't leave any room for the upper one. It still seems to engage and drive the saddle ok, but I found the engaging lever would often stick so I wanted to improve it.
I also noted the usual mini-lathe problem with the dovetails and gibs making poor contact so I expected to make some marked improvements by lapping them to a better fit.
However, the more I study the mechanism the more I think the manufacturers need to redesign it from scratch. It's quite a surprise it works at all as far as I can tell. Virtually all the dovetail in contact with the half nut is missing on one side where a circular recess has been cut for the cam type (?) mechanism that the handle turns, and on the other side the gib is held in place by two screws+washers. It looks like a total bodge and I suspect any minor attempts to improve it may stop it working by what ever mysterious means it currently functions. Are there any articles out there about this issue and ways to resolve it, because I can't find anything beyond a mention that the mechanism includes a gib?
Scrim
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Looks like I might be on my own with this one then!
Scrim

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Perhaps that's why old machines like Myford are still so popular <G>
Cliff Coggin.

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I would have replied if I had had the same experience. However I have an original mini-lathe (marketed as the Chester Conquest) which I've used since Dec. 1999 and haven't experienced this problem as it has a proper pair of half nuts. My suggestion would be to remove the new leadscrew guard, order as a spare part from Chester, ArcEuro, Warco or MachineMart(Clarke 300 lathe) the half nut machanism for an original minilathe and fit that instead of the one in the "super C3" assuming that the Chinese manufacturers are using the same castings. You won't be able to refit the leadscrew guard (new to the S C3) as is but perhaps you can modify it if you really want one - I've not found that I needed one on my machine.
Norman Billingham suggested the excellent "The Mini-lathe" book in the Workshop Series no.43, but Dave Fenner doesn't mention the Super C3 in the book as I assume it came out after the book was published and so the problem isn't mentioned as his machine has the original pair of half nuts.
Normans other suggestion of joining one or all of the Yahoo groups for the mini lathe is a good one, ask your question there - I got a lot of help from those groups when I was first starting with the lathe.
Alan
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Thanks folks. For now I've made do with the following which has improved things a lot: I fitted a large diameter thin spring washer between the apron and the 'cam' type disk that's rotated by the engaging handle. I cleaned up the face of the handle which bears on the apron by facing in the lathe (with no apron you have to hold the saddle against a bed stop and use the top slide to feed the tool to the left). I replaced the two soft washers which hold the gib in place with two strong steel 'washers'. I used the ends of the two feeler gauge strips that already had holes bored in them so all I had to do was cut off with a Dremel and clean the edges up.
With adjustment of the gib it now has a smooth and precise feeling action. It doesn't appear that using a single half nut detracts from the mechanisms function, so I won't worry about that as I like having the guard to keep swarf off the lead screw. ARC actually offered to send me the upper half nut when I bought the Super C3, but I decided not to take them up on it for some reason.
Scrim
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No personal experince, but there's a whole book about the mini lathe by Dave Fenner - #43 in the Workshop Practice series. Don't know if it covers your problem though.
You can also look in Yahoo grops for 7X10 mini lathe group or look at http://www.mini-lathe.com/
There's a vast amount of information on these little lathes out there.
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http://www.mini-lathe.com/
Lot of mods for the mini-lathe there:)
--
coriolan
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