Mini lathe feed

Hi again, ok after fixing the potentiometer with your help i now have an issue with my feed . The long screw bar turns , but when i lift the lever it does not engage and move along like it should . I can move along with the wheel but not the automatic feed

Either the lever is not engaging the half nut  ( not adjusted correctly ) or the half nut is worn

Edited By John Rudd on 13/01/2021 11:17:31

I do not have a mini lathe. It looks like the half nut is either stripped or is not engaging with the lead screw. Are there a lot of chips in the halfnut stopping it engaging?. Only stripping out the apron will give the correct answer.

regards

Is the answer in the word "lift". The lever should be pushed down to engage the leadscrew.

Keith

When engaged the wheel won't work and vice-versa.

The half nuts are adjustable in several ways, there is also a hidden grub screw that controls how closely they mesh (Incidentally Ian Bradley suggested such a screw as an upgrade for the S7).

Neil

My mistake , i was not by the lathe when i wrote this , i could not remember which way engages 🤣

I will investigate this , no idea what the half nut is but i will look up on the Internet so i know what im looking for 👌🏻

I was not clear, i ment i can use the lathe with the manual wheel, but it will jot move automatically. Also my lathe will not engage reverse feed fo some reason-it never did ?

You need to check the geartrain/change gear set up behind the left cover.

1 with lathe unplugged, first release quadrant to free change gear mounted to leadscrew from any other gears in the train.

2 turn the change gear on leadscrew manually to check leadscrew rotates, if so, engage carriage feed lever to check for expected movement forward and reverse - if carriage is not moving then investigate for correct movement of half nuts (by peering at right end of carriage with a torch to confirm that the half nuts move together and apart to clasp the leadscrew).

3) if that checks out alright, check that the change gears you expect to have in the train can be made to mesh correctly and check by rotating chuck by hand to confirm motion all through the gear train to the leadscrew - if not look for change gear mounting issues or potential damage (grub screws or nuts to tighten etc)

4) check operation of tumbler reverse jockey wheels - correct engagement etc

5) if all the above is Greek to you, download this manual....

g0765_m.pdf (grizzly.com)

Edited By Martin of Wick on 13/01/2021 14:36:51

5) if all the above is Greek to you, download this manual....

Bloomin’ ‘eck, Martin. That is 76 pages!🙂

Just so that Darren can get to grips with some of the terminology this picture is taken from his video when trying to engage the feed or screw-cutting handle (lever)

It seems that the half nuts are not travelling full distance although the video is too dark to see if there is actually an upper half nut, if there isn't that might explain the problem!
 

For further lathe parts info try this ***Data Page*** on my website.

John

Edited By Journeyman on 13/01/2021 15:36:50

Almost immediately behind the lever is a threaded clamp thingy that engages with the leadscrew when the lever is operated. The 'nut' is in two halves, and working the lever brings them together to mesh with the screw with a kind of scissor action.

It's hidden behind the apron, but you should be able to peer at the clamp from the side &/or underneath to see what happens when the lever's moved. One possibility is that the lead-screw isn't parallel with the top of the bed, too high and too low both cause failure to engage. The tail-stock end sits in a height adjustable block, which is easy to move deliberately or accidentally.

The mechanism is quite robust but they can get out of adjustment or wear out. Probably an adjustment fix unless the lathe has had a hard life.

Dave

.

... and it downloads in seconds

[the internet wonderful if you leave out all the evil stuff]

MichaelG.

If you look at Journeymans photo you can see a couple of slotted screws, These act on a crude dovetail which constrains a slide which the half nut is worked with. I find that these screws come loose and prevent the nut from locking in place. It is a bit of a fiddle to get this set up right but I find that this is what is needed most of the time. At some point I will take mine off and do something more positive with it. Despite the swarf aspect I think two half nuts are better than one

I did another video , thankyou guys for all your replies so far . If I understand correctly should there be another top part of the lower half nut?
https://youtu.be/fAt4H0ad9lg

Edited By Darren Keats on 13/01/2021 17:05:33

Check that the top half of the nut is moving down like the lower is moving up.

Also try it when the lathe is running slower and make sure the carriage lock is not done up.

Edited By JasonB on 13/01/2021 17:12:03

I use it for shaping acrylic bar, so it just needs to move across quickly to get the job done level, as with the manual wheel its a bit jerky. I have never cut metal on it , just to make mm perfect acrylic pieces similar to pen blanks

There is no top half, just this lower part of the half nut . Maybe its stuck above but i cant see it?