Mini lathe feed

This topic has 43 replies, 17 voices, and was last updated 10 February 2021 at 20:20 by Howard Lewis.

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13 January 2021 at 10:44 #20095
Darren Keats
Participant
@darrenkeats48928
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13 January 2021 at 10:44 #519518
Darren Keats
Participant
@darrenkeats48928
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
13 January 2021 at 10:56 #519523
Darren Keats
Participant
@darrenkeats48928
https://youtu.be/e7Ra4Yh3B-k
13 January 2021 at 11:15 #519526
John Rudd
Participant
@johnrudd16576
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
13 January 2021 at 11:17 #519529
Oldiron
Participant
@oldiron
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
13 January 2021 at 11:43 #519533
KEITH BEAUMONT
Participant
@keithbeaumont45476
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
13 January 2021 at 12:36 #519539
Neil Wyatt
Moderator
@neilwyatt
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
13 January 2021 at 13:58 #519551
Darren Keats
Participant
@darrenkeats48928
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 🤣
13 January 2021 at 14:00 #519552
Darren Keats
Participant
@darrenkeats48928
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 👌🏻
13 January 2021 at 14:01 #519553
Darren Keats
Participant
@darrenkeats48928
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 ?
13 January 2021 at 14:34 #519566
Martin of Wick
Participant
@martinofwick
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
13 January 2021 at 15:14 #519576
not done it yet
Participant
@notdoneityet
5) if all the above is Greek to you, download this manual….

Bloomin’ ‘eck, Martin. That is 76 pages!🙂
13 January 2021 at 15:30 #519578
Journeyman
Participant
@journeyman
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
13 January 2021 at 15:31 #519579
SillyOldDuffer
Moderator
@sillyoldduffer
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
13 January 2021 at 15:44 #519580
Michael Gilligan
Participant
@michaelgilligan61133
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.
13 January 2021 at 16:06 #519584
HOWARDT
Participant
@howardt
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
13 January 2021 at 17:04 #519591
Darren Keats
Participant
@darrenkeats48928
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
13 January 2021 at 17:07 #519592
JasonB
Moderator
@jasonb
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
13 January 2021 at 17:10 #519593
Darren Keats
Participant
@darrenkeats48928
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 🙏🏻👍🏻
13 January 2021 at 17:13 #519594
Darren Keats
Participant
@darrenkeats48928
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
13 January 2021 at 17:14 #519595
Darren Keats
Participant
@darrenkeats48928
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?
13 January 2021 at 17:15 #519596
JasonB
Moderator
@jasonb
This is what should be happening
13 January 2021 at 17:18 #519597
ega
Participant
@ega
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 believe Martin Cleeve made the same suggestion.
13 January 2021 at 17:26 #519600
Michael Horner
Participant
@michaelhorner54327
Hi Darren

If there is a swarf guard over the top of your lead screw there may only 1 half nut fitted.

Cheers Michael.
13 January 2021 at 17:32 #519601
Darren Keats
Participant
@darrenkeats48928
Posted by JasonB on 13/01/2021 17:15:25:

This is what should be happening

There is no top half that i can see . It must be stuck up out of view as it has been working up until today
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