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Refitting belts on Myford Tri Leva lathe

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John Greenwood 209/04/2019 18:00:08
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I have successfully (I think) inserted a set of new belts on my Myford Tri Leva lathe. It looks like I need to adjust the individual belst and the what I think is the adjusters have an unfamiliar head:

What tool do I need?

Also the head stock is very stiff. The white metal bearings were a bit scored

V8Eng09/04/2019 20:58:45
1280 forum posts
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I have owned my Tri Leva for many years and have never seen a special tool for these although somebody else may know better.

My adjusters rotate using simple finger pressure after the roller arm has been pushed inward to release the slotted end of the adjusting screw from engagement with it, the slot must be returned to vertical alignment again after any adjustment and check it is properly engaged. I find this operation a bit tricky to do and difficult to explain so hope it makes some sense.

A manual helps greatly do you have one?

Your screws look a bit chewed up so maybe somebody tried turning them with pliers or something without disengaging the slotted end.

Here are photos of the screw and slotted end, hope that it helps explain things.11c91a29-aeef-4533-a96f-817c74f212c9.jpeg

76e18194-5dc2-4897-9f6e-70191397834b.jpeg

Edited By V8Eng on 09/04/2019 21:06:23

choochoo_baloo09/04/2019 23:26:17
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Posted by John Greenwood 2 on 09/04/2019 18:00:08:

Also the head stock is very stiff. The white metal bearings were a bit scored

Hello John. V8Eng and I were discussing Tri Leva maintenance the other week.

  1. I was adjusting those thumb screws over the weekend. Those thumbscrews have a slot milled in the end that cup the pulley blades (see V8Eng pictures above).
  2. You thus need to push the pulley blade from the front of the unit, since a spring holds the blade within the slot when that lever is in the up position.
  3. Whilst the blade is held back (under spring tension), simply twist the knurled head to get the require pulley-on-belt tension once that lever is depressed.

Hence do NOT attempt adjusting the thumbscrews till the blade is away from the slot - you will simply bugger up the thread as V8 has alluded to!

Ask again here if I can help any more - the chaps on this forum have been very helpful to me over the years nerd

John Greenwood 217/04/2019 10:48:35
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Thanks for the replys, those pictures make it really clear how it works!

I tightened these adjusters until the belts started gripping but the stiffness of the headstock bearings meant that fastest speed slipped with a squealing sound and with the slowest speed the belt slipped out of the pulleys.

I clearly have not got things back right.

V8Eng17/04/2019 14:12:50
1280 forum posts
27 photos
Posted by John Greenwood 2 on 17/04/2019 10:48:35:

Thanks for the replys, those pictures make it really clear how it works!

I tightened these adjusters until the belts started gripping but the stiffness of the headstock bearings meant that fastest speed slipped with a squealing sound and with the slowest speed the belt slipped out of the pulleys.

I clearly have not got things back right.

 

 

 

Hope none of the following is teaching Granny how to suck eggs and sorry if it is!

Was the spindle running ok before you changed the belts?

If it was then have you reassembled the shaft parts and set things up according to the manual?

May be a silly question: but did you make sure the bearing caps were put back as they were originally and that none of of the bearing shims were lost or misplaced during the belt change?

Hope you realise that the belts normally should slip until the relevant lever is pushed down, if the shaft is that tight then I would not be attempting to run the lathe until it is sorted out.

Maybe somebody can come in on here with more experience of these matters, mine is very limited.

 

Edited By V8Eng on 17/04/2019 14:15:40

John Greenwood 218/04/2019 10:48:23
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Thanks for the suggestions.

Yes, the spindle was working properly and I think I have put the parts back to where they came from, which also seems to corespond to the manual.

In particular, the headstock parts went back to wher they came from, including the shims, although they might have got swapped back to front.

I do realise that the belts normally slip, but thank you for confirming this.

I note your view that it would be unwise to run the lathe until the main bearing has been sorted. I tend to agree.

I suppose the next step (in a weeks or so) will be to dismantle the headstock.

A Smith18/04/2019 12:24:06
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2 photos

I've owned a Tri Leva since the mid eighties and have changed the belts about every five or six years. Once you get the hang of the adjustment process, it all works well. The speed selection levers double as clutches so stopping, starting and speed changing (between the three speeds available) is almost instant. Engaging & dis-engaging the back gear is a bit of a pain, it's more difficult to raise the spindle/ belt cover on a Tri Leva, so it's easier to leave it in position and just use the cover behind the bearing as Nottingham intended.). I have an Allen key with a shortened business end, just for this purpose.

It is important to tension the motor drive belt first because that will affect the distance between the three drive pulleys and the spindle. I now use one of the segmented, cogged belts & it has been completely satisfactory. To get the right grip, this belt should be tensioned so that there is no slack but it's not tight enough to pull the driving (top) spindle down appreciably.

Having done this, with the other three belts slackened right off, adjust the tension of each belt until it just grips. This may require a lot less tension than you expect. The belt tension should be just about discernible as the speed selection lever is pulled down. If it slips when you're taking a normal cut, just tweak it up slightly.

With the motor running and with all three levers right up, the main spindle (mandrel to some) should not revolve at all.

Hope this helps.

Andy

SillyOldDuffer18/04/2019 12:57:54
4415 forum posts
957 photos

I'm worried about John's comment in his first post: 'Also the head stock is very stiff. The white metal bearings were a bit scored'.

I've never seen a Tri-leva in the flesh, but I think they work by deliberately slipping two belts whilst tightening a third to select the wanted drive ratio. So, if the headstock were 'very sfiff', that might produce 'time for new belts' symptoms, when the real problem is the stiff headstock making it impossible to pre-set the belt tensions properly. Is it a good idea to adjust a Tri-leva's belts whilst the spindle bearing is sticky possibly damaged?

In ignorance, I think I'd start with the headstock problem. Blocked oil-way perhaps?

Dave

John Greenwood 218/04/2019 17:36:04
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"Very stiff" means that that, with all three belts a bit loose, I need to use a bit of wood about a foot long in the chuck jaws as a lever to be able to turn it, with some effort.

This belt renewing was precipitated by one of the belts getting jambed while in use with the headstock revolving freely. Therefore it is something I did when taking it off.

I think from the comments above the belts are nearly as they should.

choochoo_baloo19/04/2019 23:34:24
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183 forum posts
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I've replied inline to your reply Andy. I am also struggling to fine tune my Tri-Leva.

Posted by A Smith on 18/04/2019 12:24:06:

It is important to tension the motor drive belt first because that will affect the distance between the three drive pulleys and the spindle. I now use one of the segmented, cogged belts & it has been completely satisfactory. To get the right grip, this belt should be tensioned so that there is no slack but it's not tight enough to pull the driving (top) spindle down appreciably.

CCB: Just to be clear, are you referring to the motor to counter shaft (~6 in diameter pulley) belt? A "Fenner" link belt? I have the original V belt and it's looking a bit tired...

Having done this, with the other three belts slackened right off, adjust the tension of each belt until it just grips.

CCB: Sorry I don't follow - the 2 cone pulleys (countershaft & spindle) are fixed relative to each other - hwo can one adjust them? Or are you referring to to the slotted thumbscrews for this "adjust the tension of each belt"?

This may require a lot less tension than you expect. The belt tension should be just about discernible as the speed selection lever is pulled down. If it slips when you're taking a normal cut, just tweak it up slightly.

With the motor running and with all three levers right up, the main spindle (mandrel to some) should not revolve at all.

Hope this helps.

Andy

John Greenwood 201/05/2019 11:37:30
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I had concluded that the the main bearing was much too stiff and needed to be sorted before adjusting the belts.

I removed the top shell of the front bearing and gave the exposed sufaces a very fim wipe wth kitchen wipe and three-in-one oil

upper bearing

Shaft bearing

I then reassembled the top shell with the bolts tighten but not hard. I find that I can turn the shaft with my fingers or with any of the three belts.

I propose to tighten the bolts hard and see if the it gets stiffer.

Should I expect to need to "run it in"?

V8Eng02/05/2019 09:59:25
1280 forum posts
27 photos

Bump.

John Greenwood 206/05/2019 10:16:36
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Following on from my last post, I ressembled the tri-lever meshanism and with a bit of adjustment was able to run the machine on all three speeds. I tightened the shell screws as tight as I could, and there was no discernable increase in stiffness in the bearing.

I reassembled all the rest of the parts and ran the lathe and tested the levers. There were some squeaky sounds and a few times the fastest speed belt became disengaged.

I made some quite small adjustment to the alignment of the belt pulleys and now it seems to back to the status quo (anti bellum).

Now I can get back to the job I was doing!

Thanks to all of you that have contributed to this thread.

Cheers

John

V8Eng06/05/2019 12:54:33
1280 forum posts
27 photos

Really pleasing to hear that it worked out well in the end.

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