Mini lathe feed

Thankyou Michael , just watched that 👍

Edited By Darren Keats on 10/02/2021 18:35:50

https://www.arceurotrade.co.uk/machineguides/Super-C3-Half-Nut-Conversion-Guide.pdf

may as well do this conversion to 2 half nuts while im at it

I would suggest that you start by setting the half nut against the Leadscrew , There won't be enough room to between Bed and Apron to access the screws. You already have the Apron off the Saddle.

My method would be to nip the cross head screw so that the half nut is tight, but not immoveable,. Fit the Apron back onto the Saddle, securely, and whilst rocking the leadscrew to and fro, engage the half nut. Then with a long screwdriver or a bar, lever the half nut fully into mesh with the Leadscrew. But do not use excessive force.

Remove the Apron and fully tighten the cross head screw. At the same time, slacken the two capscrews and retighten so that they nip the support block.

Refit the Apron again, and lever the support block to just touch the Leadscrew. Do not use excess force.

Remove the Apron, again and fully tighten the capscrews.

Refit the Apron, for, we hope, the last time.

The finest feed that you can get with the standard gears will be:

20T from under the Tumbler Reverse, driving 80T on the stud. This will be keyed to a second 20T which drives a 80T on the Leadscrew (May need a spacer on the inside to keep the gears in line to mesh )

The backlash between the gears should be set by running a piece of paper (0.075 mm or 0.003" in old money thick ) between the gears.

I would start by adjusting the stud to set the mesh between the 80T on the Leadscrew and the 20T on the stud. Having positioned the stud on the banjo to achieve this, you can then swing the banjo to set the mesh between the 80T on the stud to the 20T beneath the Tumbler Reverse.

Running gears without backlash will produce noise and wear.

This will give the finest feed that the standard set up can provide., 0.09375 mm (0.003669" ) per rev of the chuck.

80/20 = 4 so the overall reduction is 16:1, Hence 1.5 mm / 16 = 0.09375 mm .

(It is assumed to be a Metric machine with a Leadscrew pitch of 1.5 mm rather than an Imperial with 16 tpi )

Ideally, the finishing tool should have a small radius on the nose. And obviously needs to be set on the centre height of the Mandrel.

HTH

Howard