New Member, New Lathe. Smart & Brown Model A (Mk 1/1.5?)

Hi There,

I'm a new member to the forum though did hold a magazine subscription for a few years, a few years back.

I've just moved back to Gods Own County and bought my/our first house,) I knew my garage was begging for a lathe!

By fluke I ended up going to see a Smart & Brown Model A a month back which looked in pretty good nick (minus the switch gear) and thought it'd be a steal.

It was sold as 3 phase & motor not working, but a bit of work digging it out from the cabinet and it turns out its a Tuscan Engineering single phase induction jobby. Works fine, bearings sound brand new, sat on it's arse it runs smooth with no vibration or anything. Annoyingly, having just bought a nice lever arm reversing switch, the starter coil is hardwired in so it only spins one way, but I've got the lathe turning.

With the belt slackened, the 3 speed gearbox changes fine, but I'm struggling to get the "direct drive" (Back Gear 'Out' to function, and hoped someone here might be able to help. I have the book from Lathes.co.uk but it's somewhat lacking as a manual goes and I'm not really sure which model it is, whether its the Model A Mk1 or 1.5.

On the same topic, I've got some fair backlash in the cross slide, any knowledge on where to start with thatone would be good. Plus, the headstock loves to fire out oil when it's running with the cover open - is this normal? And where should I be topping it up? The manual pump just has a dead cavity when I take the cover off. I'm sure I can work all this out in time but if anyone has some experience I'd love to hear it!

I've applied to join the old yahoo group which I found in another thread here, but figured it may be worth asking here as well!

I've attached some pictures below.

tl;dr Hi, I'm new here, here's my new lathe - can you help me fix the "direct drive/"open belt" function?

Thanks!

Duncan

Looks like a cracking machine, sorry I have no info

May benefit from a VFD conversion

Does look like a Mk 1.5 machine having the later back gear engagement but sat on the earlier style cabinet. If your problem is getting the back gear to disengage properly, you might have the same issue that I did 30 or so years ago with my Mk 2.

Operated via the backgear lever, there is a multi tooth dog clutch inside the headstock pulley; this is held in place by three or four 3/16" BSF capscrews. If one of these breaks; as it did on mine there isn't the room for the screw remnant to escape completely, but it will often/most of the time keep the backgear from fully disengaging when the screwhead gets stuck in one of the opposing dog clutch teeth. An exploded diagram is pretty much essential as an aid to stripping the spindle down in order to get access to replace the capscrews. Being as I hadn't seen a manual and it was pre 'internet ubiquity' when I did this repair, I puzzled for many hours stripping it down before I found a hidden tiny pin which retained one of the many spur gears on the rear of the spindle.

These are superb machines IMO. Of the lathes I used as an apprentice, an S & B model M was easily the best, The Model A has the same accuracy and rigidity, but has the added advantage of the Norton style gearbox too.

I could be misunderstanding you here, but I wouldn't describe the backgear as not disengaging - the back gear as I understand it is the eccentric engaged gear which transfers power between the two gears on the right side of the headstock image above.

The problem is when it is disengaged the pulleys spins free and does not engage direct drive with the spindle, massively limiting the number of output speeds.

From your description, it sounds as though the dogclutch isn't engaging?

So your inner and outer spindles are not being locked together by the dog clutch when the back gear is disengaged? If that's your problem, the dog clutch either isn't being engaged when the machine is in direct belt drive mode or the dog clutch is engaged but the retaining capscrews that live inside the headstock pulley are either missing or have sheared off.

My problem was that the capscrew remnant in the dog clutch was keeping the inner and outer spindle locked together when the backgear was engaged. This of course meant that the headstock would not rotate when the lathe was in backgear mode.

As I'm sure you've seen already on your machine, the lever that engages the backgear also operates a fork that engages/disengages the dog clutch. The dog clutch needs to be disengaged when the machine is 'back gear' mode and engaged when it is in 'direct drive' mode.

Exactly right on the first one

No, not at all, in fact that was the question I was going to ask, as I cant see any way a clutch could be engaged at the moment.

As below, the "In/out" lever looks to turn the shaft in red below which in turn rotates the eccentric (blue) onto which the backgear gears are mounted - there doesn't appear to be any forks anywhere to operate the dog clutch and I haven't noticed them on the drawings - is there any chance you could indicate on one of these drawing roughly where I should be looking for it?

Thanks!

There will probably be a hex socket on the left hand face of the pulley, where the red line is on your photo. This needs to be turned about 180° to engage the internal dog clutch to lock the pulley to the spindle. Make sure it is locked by rotating the pulley by hand before starting the motor as otherwise the clutch will be damaged when the motor starts up.

Martin C

Edited By Martin Connelly on 06/09/2021 13:00:42

From this photo I can see that you have the Mk1 backgear setup, I hadn't noticed that detail in your first batch of photos. So, Martin Connelly's photo looks to be what you should have.

This is the Mk 2 setup with the fork that engages/disengages the dog clutch as well as engaging/disengaging the back gear when the in/out lever is operated. Apologies for any confusion caused.

Edited By Stueeee on 06/09/2021 14:02:38

Edited By Stueeee on 06/09/2021 14:03:47

Perfect, Thanks!

The book does mention that socket but given that I haven't got the original tool it talks about I was hoping that wasn't the case - would I be correct in thinking that the socket needs to be turned 180* to disengage direct drive and re-engage the back gear every time a speed change is wanted?

I'll investigate tonight with a chopped down hex key.

If so - that fork arrangement would seem like a major part of the assembly to miss out in the Mk1 model!

Thanks All!

Stueeee - there is a little rectangular cut out into the top of the curve to the left of the lid, yours has a little handle in it but mine doesn't and it's painted shut - what does this cover?

Jinks, Have a look here on the S & B group **LINK**

May find something of interest or help

John

The photos provided by Stueeee show the reason why your lathe spews out oil, there should be a cover for the backgears. It has no function but to contain the oil, so it might be possible to make something out of sheet metal. The screws which hold it to the headstock are 2BA.

With a shortened hex key, you turn the backgear lock clockwise to disengage the pulleys from the spindle, and then you can engage the backgears. After using the backgear, you first disengage the backgear eccentric and then using the hex key in an anticlockwise direction, the locking dog is sprung back into place to lock the pulleys to the spindle. If you hold the chuck and slowly turn the pulleys, you should hear the dog spring back into place.

The cross slide backlash is caused by wear on the 1/2" x 5 ACME left hand thread. There is limited antibacklash adjustment on the nut which might help.

Be wary of running in reverse with a screwed spindle machine.

Edited By old mart on 06/09/2021 15:21:10

To keep it looking original I think a 3D printed one would fit well, when I can get my printer back up and running - useful to know the screw size! Picked some up this morning from my local supply shop on the way to work! Looks like the smaller switch plate mounts with 2BA.

Picked up some Imperial Hex keys at the same time (surprised to find I didn't have any imperial tools at all!) and got the dog clutch working - it seems dangerous to have a clutch which is operated by an internal socket locking up against a gear train which is operated from the outside - the engaging fork in the Mk1.5 onwards seems to me to be an essential part of the machine. Working out a way to add this feature in may be a project for the distant future.

Reverse would be a useful feature to have for threading but I'm sure I can get around without it!

Thanks for all your help! Does anyone know where the oil resevoirs for both the apron and the backgear train get filled?

You will find that the threads on the model A are either BA or BSF. I could try making a sketch of the gear cover which would help with a 3d print. I don't think the change to the later backgear lock is viable. The apron is filled at the lower right hand end level/filler. The backgear train can be filled simply by squirting oil down between the gears, you would normally have to remove the cover, (missing) to do that. Just deep enough to submerge the bottom of the lower gear. It is the Mk2 that has the improved backgear assembly, yours is a Mk1 or 1.5.

Edited By old mart on 07/09/2021 20:05:04

Edited By old mart on 07/09/2021 20:06:42

Jinks, you are correct in that the back gear clutch on the pulley needs to be disengaged when you want back gear again. If you have the clutch engaged and the back gear engaged at the same time it will effectively lock the spindle which is useful when hand tightening up the original collets and drawbar if you have them. The small rectangular cut out with a small knob on top is purely for access to the rear bearing adjustment rings. It should be lightly held in place by a small sprung ball.

A 3D printed cover for the bull gear will be splashed with oil and may not survive very long unless you are sure you have an oil proof material. The addition of a sheet metal liner would be a good idea. The oiling point on the far side of the head on the right should fill the back gear oil reservoir and there is a wick that takes oil from this reservoir up to the bearings. Once fitted the bull gear cover does not need removing except for bearing adjustment.

Martin C

Thanks old mart, I'll keep that in mind. I had badly mis-read the manual and got confused and had been thinking about the manually operated pump for the headstock end gears, which after a re read clearly says is topped up & drained from the t-piece at the back. Embarrassing how much I missed on my first read through! Also worrying as I had opened the drain and found only sludge on the plug and no oil content! Time for some fresh oil!

Hi Martin, I can see the benefits but it seems like an easy mistake to start with both engaged! And easy to not get the dog teeth fully engaged whilst starting, potentially damaging the clutch!

Sadly, I don't have the drawbar, collets or collet holder (unless they go straight into the spindle?). Are these standard size collets?

PLA & PETg are both meant to be resistant to oil, and a dunk test and time will tell I would suspect - worst case it gives me reason to try lost PLA investment casting at home!

Thanks for your help & advice!

I did notice both the motor faltering quickly and the link belt drive (between the motor and lower gearbox) struggling to not slip in the direct drive mode so I may be in the market for a new one soon, but first I better whip it out and check it over.

I would point out on my Model M that I took the original 3 phase motor off and put on a new modern motor as I was going to use a VFD and they are good at damaging the insulation and bearings if used on older motors. The new one, even though it is a higher power rating, is lighter than the old motor by a significant percentage. Since the tension on the belt is a result of it supporting the weight of the motor on its hinged support it is more prone to slipping with the new motor and I have to have a couple of heavy lumps of metal on top of the motor to give sufficient tension to the belt. Maybe if the Model A is similar you do not have the original heavy motor on your machine.

Martin C

I would point out on my Model M that I took the original 3 phase motor off and put on a new modern motor as I was going to use a VFD and they are good at damaging the insulation and bearings if used on older motors. The new one, even though it is a higher power rating, is lighter than the old motor by a significant percentage. Since the tension on the belt is a result of it supporting the weight of the motor on its hinged support it is more prone to slipping with the new motor and I have to have a couple of heavy lumps of metal on top of the motor to give sufficient tension to the belt. Maybe if the Model A is similar you do not have the original heavy motor on your machine.

Martin C

The blanked off point on the left end of the top of the headstock is another project for 3D printing. The little insert that should sit in there is to provide an access point for adjusting the left hand spindle bearing. You can also squirt some oil in there to lubricate the thrust bearing. If you join the group already mentioned, they may have free downloads of S & B manuals and parts drawings. Otherwise, you can buy the full print from "lathes UK".

Thanks Martin, I'll have a look.

I've got the manuals available on the group, although the drawings available are certainly helpful, even if not entirely clear!

I bought the lathe with 2 booklets which I believe are the print from lathes.co.uk.

Just thought I'd shoot an update with the switch plate roughly mounted, needs a lick of paint and the rev/off/fwd decal taken from the barrel switch adding but it works for now.