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Mini lathe feed

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Darren Keats13/01/2021 10:44:02
23 forum posts

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

Darren Keats13/01/2021 10:56:38
23 forum posts
https://youtu.be/e7Ra4Yh3B-k
John Rudd13/01/2021 11:15:09
1450 forum posts
12 photos

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

Oldiron13/01/2021 11:17:52
975 forum posts
40 photos

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

KEITH BEAUMONT13/01/2021 11:43:15
166 forum posts
38 photos
Posted by Darren Keats on 13/01/2021 10:44:02:

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

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

Keith

Neil Wyatt13/01/2021 12:36:42
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Moderator
19033 forum posts
734 photos
80 articles

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

Darren Keats13/01/2021 13:58:54
23 forum posts

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

Keith

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

Darren Keats13/01/2021 14:00:18
23 forum posts
Posted by John Rudd on 13/01/2021 11:15:09:

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 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 👌🏻

Darren Keats13/01/2021 14:01:54
23 forum posts
Posted by Neil Wyatt on 13/01/2021 12:36:42:

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

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 ?

Martin of Wick13/01/2021 14:34:11
249 forum posts
5 photos

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

not done it yet13/01/2021 15:14:09
6809 forum posts
20 photos

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

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

Journeyman13/01/2021 15:30:03
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1159 forum posts
235 photos

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)

halfnut.jpg

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

SillyOldDuffer13/01/2021 15:31:41
Moderator
8683 forum posts
1967 photos
Posted by Darren Keats on 13/01/2021 14:00:18:
Posted by John Rudd on 13/01/2021 11:15:09:

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 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 👌🏻

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

Michael Gilligan13/01/2021 15:44:13
avatar
20182 forum posts
1053 photos
Posted by not done it yet on 13/01/2021 15:14:09:

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

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

.

... and it downloads in seconds

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

MichaelG.

HOWARDT13/01/2021 16:06:01
908 forum posts
39 photos

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

Darren Keats13/01/2021 17:04:58
23 forum posts

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

JasonB13/01/2021 17:07:23
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Moderator
22747 forum posts
2653 photos
1 articles

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

Darren Keats13/01/2021 17:10:51
23 forum posts
Posted by Martin of Wick on 13/01/2021 14:34:11:

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

this is a very useful download for someone like me who needs to identify what parts are called, appreciate this👍🏻 And to everyone else who is trying to help me 🙏🏻👍🏻

Darren Keats13/01/2021 17:13:01
23 forum posts
Posted by JasonB on 13/01/2021 17:07:23:

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

Also why have you got it running so fast if it is for feed, would even cut a very coarse thread at that rate.

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

Darren Keats13/01/2021 17:14:11
23 forum posts
Posted by JasonB on 13/01/2021 17:07:23:

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

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

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