Super 7 Lathe Clutch, Countershaft or Pulley Wobble

Maybe a red Herring, but if the countershaft is bent, the only effect might be to cause the mandrel to rotate at an varying speed (varying angular velocity ) which could cause an inconsistent surface finish.

Once the OP has cutting tools which are sharp and set at centre height, that will be one variable eliminated, hopefully, and things may become a little clearer..

To get a good surface finish, it is necessary to learn how to set up the change gears a fine feed rate, or to rotate the Saddle travel handlewheel at a steady rate.

Lets see what transpires

Howard

Yes, Noel, I was understanding the term countershaft to mean the one that sits in the headstock under the output spindle. And the same applies to the clutch plate - as I now remind myself that the S7 had a cone clutch as distinct from a plate clutch, and therefore I guessed wrongly (silly me) that the S7 had a plate clutch (while the ML7 I know can have a cone). The term 'clutch plate' was used in comments by others, remember.

Just remind me, someone, what the proper term is for the shaft which is used for low ratios. It is part of a gearbox, and the normal name for a shaft which runs alongside the mainshaft and can be engaged or not is - guess what - a countershaft. Silly me, again.

Cheers, Tim

Edited By Tim Stevens on 04/01/2021 15:32:07

"Couter shaft" brings to mind a shaft between the motor and the spindle, carrying pulleys, to provide a speed reduction.

The shaft within the headstock, carrying the back gears, which can be brought into mesh to provide greater speed reduction of the spindle, I would describe as the "back gear shaft".

"Clutchplate" conjures up an image of the centreplate in a vehicle, rather than a part of a cone clutch.

Mention of "corks", immediately pointed my mind towards motorcycles, although I have never been a biker.

Howard.

I'd call that a layshaft.

Clive,

So would I

Howard

Eagerly awaiting the 8mm tool so I can do some more testing in earnest. Should be later this week, royal mail dependant. John

Hi Tim and all, In a vehicle gear box the first motion shaft carries the clutch, one end is often supported by the pilot bush in the flywheel. This is carried by a bearing in the front of the box, the other end is carried on a needle roller bearing in or on the main shaftT.he main shaft carries the the various gears all free to rotate and selected by the sliding sleeves and if your really lucky synchro cones, once locked to the main shaft power is then transmitted out the box.The main shaft bearing is in the back of the box. Along side the main shaft is the lay shaft carrying the lay cluster, a collection of gears machined out of one piece of steel. The lay cluster is rotated by the first motion shaft. This is a very basic description. Noel.

Motorbike gearbox secondary shafts are referred to as both layshaft and countershaft, depending on which factory workshop manual or parts book you take as gospel. Countershaft seems more common in recent years. So BSAs had layshafts, Hondas countershafts. Harleys have countershafts and have done so since day one so perhaps that is where it came from?

Edited By Hopper on 05/01/2021 01:59:52

Yes, set gibs for free movement but no slack.

Bent countershaft? Maybe. Maybe not. There is not much of a wobble there. My flogged out fixed ML7 pulley wobbles more than that, with no noticeable effect on finish of the job. Rubber belts, if new, are very flexible and forgiving if not run guitar-string tight.

And there is a pushrod up a hole in the middle of that counter shaft so if it were bent very much the pushrod would be binding.

You may just have a slack countershaft bearing. This is very common. To test that, loosen the belts and leave clutch engaged, grab the pulley and see if you can feel any up and down movement of the shaft in the shaft bearing on the H frame behind the clutch. Put your finger in there and feel for movement. Should be a thou or three there. If excessive, like 10 thou or more, you can press in a new Oilite standard sized sintered bushing with a nut and bolt and flat washers.

To check for bent shaft you would have to pull off the clutch then rotate the countershaft by hand with belts slack and observe the end of the shaft or clock it with a dial gauge. Myfords website has parts drawings of the clutch. Not sure, but it looks like you undo the small bolts and pull the actuator off the end of the clutch, and the spring/s and then maybe a circlip and the clutch body should slide off the shaft. Should be self evident from looking at it. Not particularly complex. Maybe someone on here with a S7 has done this job and can elucidate?

Edited By Hopper on 05/01/2021 02:12:44

Harleys have countershafts and have done so since day one so perhaps that is where it came from?

I expect the term originated, not from Harley, but because the shaft rotated in the opposite direction to the ‘main’ and input shafts? So likely prior to motorcycle production, by quite some time.🙂

Not all gearboxes are arranged as described above. Most certainly the main-shaft in some (and I have pulled a few apart) is supported within the first motion (‘spigot&rsquo shaft by a quite substantial roller bearing (I would not describe the rolling elements as ‘‘needles’&rsquo inside the spigot shaft which itself runs in a large ball bearing in the gearbox case (and, yes, generally supported at the engine flywheel by a bush, needle roller- or ball- bearing - as these only come into rotating operation when the clutch is dis-engaged, so are simply a support most of the time). Indeed, some of these were open cage bearings, so never provided with any lubrication between major overhauls, in old vehicles - fit and forget!

The last such open cage example I removed had likely never been serviced from new (around1946?). Totally unserviceable as a load bearing item, but still apparently good enough for the duty it performed until the whole machine was ‘put out to grass’.

I checked my circa 1963 Myford super 7 countershaft and it too has a very slight wobble when the clutch is disengaged.

If I remember I will clock it tonight after work and see what its doing.

I have to say though that I have had this lathe since early 80's and made loads of things on it, not had any issues at all regarding surface finish or vibration.

Make sure that tools are sharp and on centre height and rake and relief angles are near what they should be for the material being machined and the lathe tool has minimum projection (overhang) from the tool post. Obviously the type of material, speed and feeds need to be correct for the job in hand.

If all this is ok then it will be time to look elsewhere, but check the simple stuff first. It is very easy to dive in and strip down components - and upon reassembling them you could introduce new additional problems.

Regards to all

Derek

It may not matter if one part of the clutch has a slight wobble when disengaged. Hopefully the other part of the clutch will not wobble, so that the cone of the clutch will centralise the part that does have play, when engaged.

This may even be a deliberate design feature, to ensure correct alignment of the two components.

What is much more important is the amount, if any, of wobble when the clutch is engaged.

Is any wobble evident when the clutch is engaged?

Elsewhere, we rely on tapers to ensure alignment!

Howard

Sorry!

Reread the thread title, so answered my own question!

Howard

Hello,

Sorry for the delay in replying, my DTI and 8mm tools arrived so I've done some tests and made a new video. Firstly I didn't change anything except the correct tool at the correct height, and I got a MUCH more acceptable cut. Very happy with that improvement. There are still a few issues though. On the video I go through sections of the lathe with the DTI checking for movement when turning. Also checking play in the chuck when the gears are locked. Best to play the video full screen and with the sound on, as you can "hear" the play in some cases.

https://youtu.be/C-VDCxl-_ew

My main notes/questions from the video (in order as in the video):

1. There looks to be not much movement when turning the countershaft (tested on the cone pulley) with the clutch engaged (motor engaged). Although I just notice I tested this with the secondary belt slack, not sure if that makes that test valid or not.
2. Movement when turning the lower cone pulleys looks ok (drive engaged for this test)
3. Movement at the chuck when turning looks ok
4. Movement at the workpiece when turning is nominal, probably from the workpiece surface more than anything.
5. Motor drive pulley is broken and someone had drilled through another grub screw. It was running true and wasn't the source of the original clutch wobble, but I bought a new one to replace anyway. I was expecting it to come with the insert strip that slots into the motor drive shaft as I can't see this insert strip in the parts diagram or available on Myford website. The insert strip of my broken pulley is bent and won't fit the tight groove with the new pulley which is unfortunate. Unless of course it is supposed to be bent? Either way it's not fitting well into the new pulley so I can't install.
6. There is a little play when turning the countershaft pulley with clutch engaged - is this ok?
7. There is play when turning the chuck with the gears locked - is this ok?
8. Cone pulleys line up correctly
9. A little side to side play in the countershaft - is this ok?
10. Belt tension - possibly too tight?
11. Now this is where it looks like the main problem is showing through the workpiece (where it actually matters). The workpiece has side to side movement when pushing. Even more when pushing with the tool. The workpiece is very tight in the chuck. This can be helped by supporting the workpiece with the tailstock. But..
12. Lastly the whole chuck moves side to side, you can see it's quite easy for me to push the chuck side to side to get movement. This can be felt/seen when actually cutting. If coming in from the end of the workpiece to take a small amount off (5 or 10thou) the tool will push the workpiece to one side and will take either no cut or not an accurate cut. Cutting deeper as it gets closer to the chuck.
13. Video finishes with showing the play in the headstock again.

So all in all everything seems to line up and seems generally ok, except when it actually counts - when putting pressure on the workpiece with a cut. This has been massively improved by proper tool height but is still a problem. This may be totally normal with these lathes in which case feel free to tell me to go and get on with it, nothing is perfect after all! But would be interesting to hear all your thoughts on the above.

Thanks,
John

Looks like worn, or incorrectly adjusted, headstock bearings. I'd concentreate on fixing that first. Everything else is nothing to worry about, but you could sort that broken pulley and bent key out as job number two.

Rob

Edit - should be able to straighten that key with a bit of judicious hammer work, or just search for "key steel"

Edited By Grindstone Cowboy on 08/01/2021 19:27:32

The way you are using your dial indicator is not telling us a lot about what is going on with the headstock bearings. Reading off the job or off the chuck body can be deceptive.

You need to put a piece of bar or pipe about 12" long in the chuck. The handle or breaker bar off a large socket set will do in a pinch.

Set the dial indicator to read directly on the spindle just behind the chuck, or if that gap is too small, set it at least to bear on the chuck backplate spigot right next to that gap. Make sure chuck is screwed on tight.

Then grab the far end of the 12" bar and try pulling it first towards you, then pushing it away. Do the same in the vertical plane with the dial gauge reading on the top of the spindle or chuck backplate and yank the end of the bar first upwards then downwards. Rotating the chuck like you are in the video tells us little or nothing about bearing play.

Up and down movement or side to side movement measured thus should not exceed ideally about half a thou.

Edited By Hopper on 09/01/2021 00:39:05

Edited By Hopper on 09/01/2021 00:41:48

The keyway, on the motor shaft and pulley and therefor the key size is dependent on the motor shaft side which is governed by the motor frame size.

For a B56 frame 3/4hp 1440 rpm motor the key is 3/16" x 3/16" on a 5/8" shaft. You can purchase a length of key steel, about 6", or packs of small keys, either work.

Check your motor shaft size and keyway size before ordering. It is most likely imperial, not metric. There used to be a smaller bore pulley available, today they list 5/8" and 16mm. Did you purchase the correct one for your motor? a 5/18" pulley will not go in a 16 mm shaft whereas teh 16mm will be a loose fit on the 5/8" shaft and will use a metric key.

The reason the key is not listed is that Myford did not supply the lathe with a motor. that was the purchasers responsibility.

Peter

You will hear the clearances, especially on the gears, since they are spur gears and will, by now, have some wear.

This, of itself is unlikely to cause major problems, since the torque to drive the lathe will take take up the backlash.

You will only be using the back gear to provide a low speed, so is unlikely to be in operation for much of the time.

Changewheels for screwcutting or automatic feed should be set by running a piece of thin card or thick paper (Say two thicknesses of writing paper ) through each mesh to provide a little backlash. Too much and they will rattle, too little and they will be noisy and wear. Gear oil, SAE 90, will be an ideal lubricant for these.

Having audible clearance in the bearings is more of a problem and needs to be reduced. It cannot, must not, be completely eliminated. For a running clearance you need a thou or so, but with lubrication maintained.

This is a drip feed lubrication with a relatively low rubbing speed. (Highly loaded white metal bearings operating at higher speeds have clearances of 0.002" - 0.004", but are pressure fed )

So if you believe that you have a problem there, your attention needs to be focused on the Mandrel bearings, in terms of radial clearance, and then end float.

HTH

Howard