Enco 109-1005 (9x20 3-in-1) Half Nut/ Lead Screw

[wilson]

I picked this up cheap, by modern standards, so I'm not too worried about its imperfections, but there's one glaring fault with this lathe(/mill/drill if you believe the marketing).

The carriage seems to be driven entirely be a single half nut.

The power feed turns the lead screw; the half nut engages or disengages with no "other half" to help out. When feeding manually, it's just turning a knob at the other end of the same lead screw. Pretty crude.

I'm wondering if anyone has recommendation on ways to improve this? I have a new nut on the way, which I'll machine down to replace the worn half nut on there (23 years and counting...), possibly with two halves so I can adjust backlash. I'm not keen on the absence of a back half, though.

 

[markba633csi]

It was probably done that way for cost reasons, and simplicity of design. A single halfnut system isn't so terrible, if it's done right.
I'm thinking--

- if you just added a "pressure foot" like a follower rest behind the leadscrew it would improve the stability considerably-
Prevent the leadscrew from deflecting backwards and prevents the halfnut from jumping out of engagement
Much simpler to do
Here's an example of a single halfnut installation on a Taig lathe that didn't have one: (lots of cool stuff on Dean's site)

A Leadscrew for the Taig

 

[wilson]

I like that idea... maybe a half a bronze 20mm bushing. I might just make an anti-backlash halfnut, and see if I can put a cam/ toggle mechanism in my engagement lever to apply a bit of pressure to my leadscrew when it's engaged, if it has a half-bushing to push up against.

 

[matthewsx]

If you have new parts on order I’d install them and see how it works as designed before modifying it.

John