Harrison L5 Metalworking Lathe (1950) Teardown & Overhaul

[Fergie 307]

First thing will be to check If you are missing anything else. The main clutch shaft is hollow and has a slot cut through it. Inside is a rod which should have a hole in it aligned with the slot. The pin, number 26, has a spline cut in the centre portion of it and is driven into the hole in the inner rod, so it projects to either side of the main shaft. Have you got the pin? If you look at the part that fits under the spring that looks like a cowboy hat, this should have a threaded insert in its friction face. It's this part that the pin bears against, part D in the cross section. Some don't have this, so only a problem if you have a threaded hole but no insert. When you strip off the pulley, so you have a bare clutch shaft you should be able to see a collar round the base of the shaft. When you move the clutch lever to and fro this should move in and out, and the pin should move up and down the slot in the shaft. They way it works is that when you move the lever to the left the pin pushes against the cowboy hat, compressing the spring and so releasing the clutch disc which should be fitted in front of the pulley. Continuing to move the lever to the left causes the collar at the back to push the discs behind the pulley together, activating the brake. When you move the lever to the right the whole process is reversed, releasing the brake, and allowing the spring to push the front clutch plate into its mating disc to transmit the drive. Hope that makes sense.

 

[Fergie 307]

Here are the diagrams that I think Fergie and I are both looking at.
The gear head of the L5 complete (shows both my 9" L5 and the later 11" L5A)
View attachment 126446

Zooming in on the clutch and brake components
View attachment 126445

It does look like I'm one disk short from the stack in my picture a couple of posts above.



With use of a lathe and a mill, it may well be possible to replicate the missing metalwork if I can get a better photo or some dimensions for the parts.

The correct friction material may well be the biggest challenge.

This will keep me busy for a few days Fergie, thank you for pointing out the problem to me !

So the plate 33 slides to and fro on six pins in the front face of the pulley, and is sandwiched between 32 and 35, both of which are keyed to the shaft. I don't know exactly what the friction material is, but it's metal. The original plates are steel with a disc of what looks like some sort of bronze bonded to either side. I will let you know when I have had a look through my bits and pieces, should be able to do it tomorrow. Always happens just when things seem to be going smoothly. On mine it was the Norton box, gave me all sorts of grief.

 

[Fergie 307]

On the pulley the pin holes are normally blind, a daft idea to my mind, as it makes the pins pigs to remove. From the factory the holes are I think 1/4 On the early machines. On ones I have repaired I drill right through the pulley with a smaller diameter, say 4mm. This enables you to easily insert a drift to drive them out from behind if you ever need to change them in the future. It's also useful if any of the pins have broken off in the holes. They are hardened so not easy to drill out. Easy enough to drill through the base of one of the others you can get out and then index around to drill in behind the broken one and drive it out.

 

[Sideways]

I have scratched my head at the drawing for a while and crawled the internet looking for photos. There's a great pictorial elsewhere of an L5A rebuild with detailed clutch photos but that is the "other" part of our exploded diagram above.
Just one phot in internet land shows an L5 and a string of parts similar to mine. I look to be minus a complete free floating disc and one or more discs of friction material associated. I guess that it simply wore out - maybe first because of inadequate maintenance - and being obsolete, the owner at that time simply removed the layer and turned a triple decker sandwich into a double decker ! I'm also guessing without studying the mechanism but I imagine that the clutch side of the sandwich was the multiple layer one to cope with the turning forces, while the brake side was a single friction layer adequate for slowing down the spindle once power was uncoupled.

The friction pads that I have left are black, almost like a rubber material. Very definitely not a hard asbestos like pad, Not even if it were contaminated by oil / grease thrown off from the roller bearing in the middle of the pulley.

I've noticed the two brass pins on one inside of my triple V pulley, now ground flush and yes, the pins are in blind holes so the reverse side of the pulley is a smooth face for another friction disc to bear on.. I was curious about that. My guess is that those pins were there because a layer of friction material was bonded to the inside of the pulley on that side only. The brass pins stick up into holes in the friction pad to transfer torque to them. Gluing the pad on wouldn't have been strong enough to resist the shear forces. This is repeated elsewhere. The pairs of pins don't go all the way through the friction material but if the pad wears down too far before being replaced, the brass pins would wear out rather than scoring the iron of the mating disc.

The old pad and any remnant of the pins was probably machined out of the pulley so that the outermost friction disc could then bear on it after the floating disc was removed from between.
I have none of the smaller springs or washers that were involved with (probably releasing) the floating disc of the clutch.

When you do have time to look through your box of bits, I'll be grateful to see what if anything you find. I won't be able to strip my clutch again for a day or two but I'll post the pictures of the spindle, anything in it and the details of the key etc when I do.

Although it's disappointing to find part of your machine has been excised, it's an interesting detective job to figure out how and why, and to discover how it should be. That's part of what makes tinkering good fun

 

[Tony Works Wood]

Excellent Tony. Thanks
Yes, I believe mine is an L5 mk3 and yours is slightly different though v similar.
Hope you are enjoying the 140. The L5 is a proper lathe with a useful capacity but it's strange to have the same 1.5" 6tpi threaded spindle on a metal lathe as they used on the graduate wood lathe !
Your newer 140 is nice step up the range !

I have some videos using the Harrison 140 on YT under the channel name EYUP TONY. They probably standardised the Graduate's spindle nose for quickness in productions as the screw cutting machines would be already set up for the L5's. I have recently acquired a Harrison Jubilee wood lathe to overhaul not as in depth as your L5 though lol..

 

[Fergie 307]

If you look at the thread Harrison L5A clutch troubles on the mig welding forum there is a photo of your clutch setup. He has the notched friction plate and drive plate the wrong way round in the picture, but the parts are the same. As standard the 5A didn't come with the high speed clutch, you had to pay extra for it. So early 5A machines have the same clutch as the 5. They standardised the high speed shaft later, at the same time as the hardened bed, about 1956/7. This design was then carried forward on all later machines including the 140. There are two types of friction plate the one on the forum pictures is the earlier type with notches around the outside which engaged with the pulley pins, these are made of a hard plastic or resin material similar to bakelite. The later type have a larger steel disc with holes rather than notches, and the friction surface is made of a metal, similar in appearance to bronze. One problem with Harrison is there is not necessarily any consistency. Partly because they were happy to build machines to a customers requirements, and partly because they have often been messed about with. The upshot is you can never predict exactly what set up you will find on any given machine. What the pulley looks like and how the driven pins are configured will be the key to knowing how it was set up originally.

 

[Fergie 307]

I know Chris Redrup on the io group has the same clutch on his, or did have. He's done a lot of mods to his head so may have changed it. Might be worth putting a message on the group.I will have a look to see what I have later today.

 

[clogs]

I was gonna say a lot of those kinda clutches used sintered bronze.....
this material is also used on older clutches used on fork lifts n yard tractors where
the norm asbestos type cluch friction material would fall aprt really quickly.....
My thinking is this lathe wont be used for production purposes an asbestos disc would be ok....
that unless u can find an original....
also there are plenty of firms outthere that will make up friction disc's tour design patern....
I had some done for the front forks of a 20-30 American m/cycle..think they were about a £5'ver each....esp as none are being made anymore...

 

[Fergie 307]

Had a rummage through the bits I have, unfortunately they are all of the later type, so no use to you. Probably worth putting out a cry for help on the Harrison lathe group. I know Chris had the same clutch on his, and there will be others who have them. If you are really lucky someone may have the parts you need. Failing that I dare say someone would be prepared to take measurements and photos for you. Once you have the dimensions then as Clogs says there are plenty of firms that can run you up a suitable disc, or supply the material. The other bits should be easy enough to make once you have the measurements.

 

[Sideways]

I have appealed to the elders
Fingers crossed !

Thanks for the other reference. I'd spotted that one photo of the parts threaded on a stick. V. glad to have your comments on how to interpret it though.

 

[Fergie 307]

Good luck. And congratulations on your work so far, nice to see the old girl in safe hands. I am sure it will reward the hard work and care you have put into it with many more years of good service.

 

[Fastdruid]

Unless yours is completely different to any I have seen before then unfortunately I think you are missing some bits. Do you know what the front of the pulley looks like If you remove the scored disc? I suspect you will find it has six holes around the inside face. These would hold the six clutch pins, which mate up with a fiction disc with six holes in it. Have you got a handbook for it? You can download one free as a pdf at vintagemachinery.org. If you look at the exploded diagram in the book yours is the older type clutch, the one that appears as the lower of the two sets of drawings of the two clutch options. The upper drawing is of the later high speed version. What you are looking at In your picture, with the two brass pins is actually the braking mechanism. Have a look at the drawings and compare with yours. I may have a spare disc, will have to have a rummage. Let me know when you've had a look, but if your pulley has the six holes then you are definitely missing the clutch plate and pins.

Sorry but it is completely different and this is wrong. You are describing the much later clutch. The manual on vintagemachinery.org is from 1965 and the clutch changed a *lot* between '49 and '65! There is also no brake fitted to this.

Here are the diagrams that I think Fergie and I are both looking at.
The gear head of the L5 complete (shows both my 9" L5 and the later 11" L5A)
View attachment 126446

Zooming in on the clutch and brake components
View attachment 126445

It does look like I'm one disk short from the stack in my picture a couple of posts above.



With use of a lathe and a mill, it may well be possible to replicate the missing metalwork if I can get a better photo or some dimensions for the parts.

The correct friction material may well be the biggest challenge.

This will keep me busy for a few days Fergie, thank you for pointing out the problem to me !

The diagram is out of the 1965 Manual which would be the "Mk4". Unfortunately Harrison in their infinite wisdom operated more on a policy of continuous improvement so the various "Mk's" are given by people to try and differentiate them rather than being official. This means that there was significant overlap between the different "Mk's" and having the correct manual for your year of Lathe is vitally important. The later manual is still useful as most bits are still really close and shared but from the look of your pictures the clutch arrangement appears closer to the ~1944-~1949 "Mk2" (ignore what lathes.co.uk says on the Mk2 being from 1946, mine is a "Mk2" and dated 1944 and I have a 1945-47 manual that is clearly for a Mk2).

I would in the first instance ask Colchester/600 Group spares (Colchester Machine Tool Solutions spares enquiry - Colchester Machine Tool Solutions ) if they have the correct manual for your machine (give them the serial from the end of the bed).

So on the assumption that it should look more like the (closer in age) Mk2, your pulley should not look like this.

But instead should look more like this. Note those two brass pins standing proud and the lack of wear to the pulley vs yours.

The part you appear to be missing is this, a DC.1 "Halo" Disc of which the early L5 had 3 vs the 1 in the later L5 shown in the 1965 manual

This is identical to the other two in the assembly (two on the left, one on the right) and it then fits like so. Locating in the two pins on the pulley to prevent it from turning.

The later L5 changed this to instead be a single floating DC.4 "Halo" disc that had 6 drive pins onto the pulley, a "Clutch Plate, centre" on the right of it and the "Clutch plate, LH" to the left. The right hand side of the pulley however was relatively unchanged with the same DC.1 "halo" disc.

It is entirely possible as that DC.1 "halo" disc was used right up until the 60's that Colchester/600 Group may have spares still. Dread to think how much but might be worth asking.

 

[Fergie 307]

Agree entirely. That's why I said the crucial thing was to look at the pulley and see what it looked like, if the six drive holes were there for example. My initial thoughts looking at it were that what we were looking at was The brake disc from the later smooth shaft type, which was why I asked what was underneath it. If this in fact the front face of the pulley itself then as you say it's the really old one, which I wasn't aware was even used that late. Only ever seen one of them, on a much older machine which was why I have thought it was the one I described. You learn something new every day.
Sideways, please accept my apologies if I have inadvertently led you in the wrong direction, but at least you have hopefully now got the full answer.

 

[Sideways]

All the advice here has been useful - appreciate it gents. Fastdruid - very good of you to sign up here and share your photos. Excellent !
Now I'm better educated, I've figured this is a 1950 year of manufacture not a 1949. Still older than me though

 

[Fergie 307]

That's the beauty of the forum, and the Harrison group. There will always be someone who knows the answer. In the case of your clutch I was mistaken. I hadn't realised that type was still in use so late, but Fastdruid has put me straight, so I have learned something I didn't know, and you have the answer to your problem. Good luck with the repair, will look forward to seeing the end result.

 

[Fastdruid]

Excuse the crudity. Spring isn't shown but that's pretty obvious where it goes.

 

[deema]

That’s super brilliant, Sideways is tracking down a suitable source of friction material. Would it be possible m, and I know this is a big ask to get dimensions of the friction plates?

 

[Fastdruid]

Friction plates are 4" OD, 2" ID and 3/16" thick. Holes appear to be 1/4" at 3-3/8" PCD.

 

[Fastdruid]

The standard L5 came fitted with a 6 pole motor (just under 1000 rpm) that gave a speed range from 21 to 480 rpm.
It was also available with a 4 pole motor and a twin speed (2 or 4 pole motor). Depending on the motor that gave top speeds up to 720 or 1440 rpm. very low by the standards of today where lathes may hit 3000 rpm or more to turn smaller parts with replaceable insert tooling.

With a 2.2kW 4 pole motor I have plenty of power available and the variable speed option. I've configured the VFD to spin the motor faster than it's design 1400 rpm. 4 pole motors are physically almost identical to 2 pole, so there will be no mechanical reason that it can't take 2800 rpm if I wanted, but when the lathe was sold with a 2800 rpm motor, it was also given a second bearing on the tail of the shaft. I won't try to go that fast. My setup will allow maximum power upto 720 rpm but thanks to the VFD can be increased to 1000 rpm at reduced torque for light cuts.

21 rpm low speed feels SO slow !

FWIW my L5 was originally also a 480rpm version. As there are no significant changes until they increased speed to 2000rpm (and even then only in the pulley) I felt confident enough to run it faster. I replaced the motor on mine with a similar 1425rpm 2.2Kw 4 pole (VFD rated 5Hz to 90Hz which would spin it from 142rpm to about 2500rpm) and kept it as roughly a 2:1 ratio so that with the over and underspeed using the VFD I had a speed range of 4RPM to 1296RPM (with roughly 720rpm at 50Hz).

After running this for a number of years I replaced the motor pulley with a 140mm (the wonders of taperlock bushes means it takes about 20mins).

Top speed now is now a rather terrifying 2400rpm (I've actually never dared do that) and at 50Hz it's a very reasonable 1440rpm or so (bit cold here, it'll gain a few rpm as it warms up).

At the same time I put a variable resistor onto the VFD so I can vary the speed with ease rather than messing with the VFD controls.

For the terror of a >75 year old lathe running at 3x its design speed, there is a short video here: 1940's Harrison L5 at 1430rpm

 

[Sideways]

It's encouraging to know that these old things can go that fast and not shake apart or overheat
That extra speed can be very valuable when you are using insert tooling and trying to get the surface feet / minute high enough.
Like minds on the choice of motor and VFD config ....

I appreciate the drawings and dimension details. I'll strip my own clutch and measure it for comparison but after that it's time to start ordering material.