Super 7 adjustments question

Now that the warm weather has finally settled in I found time to give my new (old) Myford Super 7 a closer inspection. In doing so I realized that both the spindle as well as the cross slide needed some attention.

The main spindle seemed to ‘bottom out’ when subjected to end force as when tightening up a live center in the tailstock against the workpiece. As for the cross slide, it seemed just a bit too easy to move, suggesting that that the gib needed to be snugged up.

Now, in both cases the Myford Super 7 manual has fairly clear instructions as how to adjust both the main spindle clearance as well as the cross slide. I dutifully followed those instructions and seem to have obtained good results. Unfortunately, what seems to be missing from the manual are clear and definite measurements such that I do not think that I can reliably judge the end results of these procedures.

In the case of the main spindle, to quote from the manual:

“… Move the ball bearings and spindle back until the spindle cone contacts the tapered bush and will not rotate, i.e. to a condition of no clearance. Clearance can now be set by moving the spindle forward from this “solid” position by a ¼” rotation of the rim of the locking rings (i.e. 15 degrees). This provides a preliminary setting which may be varied according to running conditions.”

What does this mean in reality? How far would the spindle move forward away from the headstock from the no clearance position in order to provide the ideal space between spindle cone and bush for an appropriate oil film? And how would I know if I accidentally moved the spindle too far? Would this result in greater amounts of workpiece deflection away from the centerline when cutting? How should I measure this?

[ Just to note that following the adjustment that I have already made, the measured runout of the spindle both on the exterior and within the ground Morse taper of the spindle (not running and with no load) is at or very slightly less than 0.01mm (= 0.00039 inch) which seems OK. ]

A similar question presents itself relative to the issue of tightening up the gib on the cross slide. Here again I quote from the Myford manual:

“ ... remove the two screws securing the cross slide end bracket so that the cross slide itself can be pushed back and backwards and forwards across the saddle manually. The four cheese head screws in the top of the cross slide should be slackened off and then just nipped, and they should be in this condition whilst the necessary adjustments are made to the grub screws. “

Again, there is no quantification of what those 'adjustments' to the gib should be.  So just how loose or tight is actually correct?   Should I be trying to measure side play or something?

Any information or tips anyone can offer to these questions is richly appreciated.

Edited By Ignatz on 08/05/2022 14:52:54

Regarding the gib what I do is slacken the cheese heads and then nip as you say and unscrew the end plate so the cross slide can be moved manually. I normally remove the leadscrew compltetely. Then using an allen key loosen all the gib screws and clean and lubricate the ways. With the slide fully engaged with the ways nip the gib screws with the long end of the allen key. I usually redo this with all the screws a second time stopping when I feel a small resistance on the key. The slide should now be unable to be move under moderate hand pressure. Undo each grub screw a small amount using the short end of the key and moving the long end through a small but identical angle (by judgement). Try the movement of the slide by hand pressure. If it's stiff slacken a little more as above until the slide moves freely. Give the end of the slide a little wobble and you should feel no movement. You are aiming for a kind of silky feel to the slide which is the feel of the oil viscosity mostly. It takes a whille to get the feel but it's actually simpler to do than describe.

The following is how Myford used to set the headstock bearings.

The gospel according to Malcolm

1. Power Down

2. Remove all belt tension.

3. Remove Chuck

4. Rotate RH collar one complete turn. (top towards you).

5. Rotate LH collar one complete turn. (top towards you).

Spindle should be completely free of front bush.

6.Loosen allen screw on collar at end of spindle.

7. Using the Allen key tighten collar as tight at it will go by hand.
Inner tapered roller races are now locked together with correct pre-load.

8. Back off LH collar one complete turn + a bit (top away from you)

9. Rocking the spindle by holding the spindle nose tighten the RH collar by hand (top away from you).

10. When you feel resistance to movement stop.

11. Collar should be just tight enough that spindle can just be moved by hand holding the nose.

12. Do up the LH collar by hand (top towards you).
You should still feel resistance when turning the spindle by the nose.

13. With the crescent wrench on the LH collar tap the end smartly with a 12oz hammer.
The spindle should move forwards by a couple of tenths and be completely free running.

14. With the lathe running slowly (lowest direct speed) put the oil gun in the front oil cup and pump until oil issues from the front bearing. (It comes out of the back and is sprayed around by the bull wheel at least it did on mine)

15. All should be sweetness and light with great rejoicing in heaven and on the earth.

After point 7 above (hand tighten collar using the hex key as a lever) Do not forget to then tighten the Allen screw to secure the collar in place.

All quite straight forward as decribed.

Thanks guys!

I've just spent a quiet hour or so, following the advice (re)adjusting my Super 7.

It all seems to be 'sweetness and light'.

As an added bonus, this second time around while setting the gib on the cross slide I happened to notice that the screws retaining the cross slide feed nut were loose. Tightened those up and as you can guess this has definitely reduced the cross feed backlash. ( Me doin' a happy dance! )

You should wind the crosslide all the way in with the end plate screws loose and then tighten them to ensure the plate and the feed nut are concentric but I'm sure you did that. The other thing is you should adjust the feedscrew coller at this point to minimise backlash.

regards Martin

PS 2 of the gib screws will be longer than the others (Nos 2 and 5) these are intended for locking the crosside when you need to without disturbing the setting.

Edited By Martin Kyte on 08/05/2022 18:22:48

Thanks, Martin.

Yes, already figured out that part about winding the cross slide all the way in before tightening the end plate, but I will go back and double check the feedscrew collar. The backlash is already drastically reduced, but I don't mind trying to make it a bit better if at all possible.

There are NO taper roller bearings on a Myford S7 ! It has 2 angular contact ball races on the rear end of the spindle (mandrel). Like so many things in the past, adjustment was by feel not measurement, that's why there are no figures given for setting the headstock bearings. IF it gets hot it's to tight ! Good luck Noel.

The headstock bearing adjustment makes a big difference and it is worth getting it right. If it is too tight or too loose, the tapered bronze bush wears, and that is quite hard to replace and scrape back in.

Get the proper C spanner. Anything else just chews up the castellated nuts. Once those are gone get some new ones. You need to make a fine adjustment here, and it's just not possible without the right spanner and well fitting nuts.

Actually it's quite hard to get the fineness of adjustment if the bearings are shot too. If everything is good the line between too tight and just right is quite clear. If you can't find the boundary replace the nuts/bearings. Don't lose the shim between the two bearings when you change them. Make sure you fit the bearings the correct way around.

You don't need the bearings with the super duper ceramic cages. Brass cages are nice, but the plastic ones are just as good. I don't know about inflation but you could change the bearings and the nuts for less than £100. The whole machine can be transformed if the ball races were shot.

Mine gave better finish, more accurate work, and it was happier with a much deeper cut. It was also much happier (and quieter) at top speed.

Edited By Andy Ash on 09/05/2022 01:54:18

Can anybody please tell me how warm a correctly adjusted super 7 headstock should run and also how much oil it should use. Mine stays cold even at top speed and I suspect the bearings are slightly loose.

Let me start the bidding, Baz

The headstock temperature should stabilise at ‘warm-not-hot’ … which I would estimate as 40 to 50 °C in a comfortable environment.

There may be numbers available somewhere, but I have never seen them.

MichaelG.

If you have a DTI then check for ANY movement in ANY direction, that will tell you if it's to loose. If it is then adjustment is on here, But get or make C spanners to adjust, I altered ER32 spanners to fit (arc) ! Noel.

Rule of thumb fitters use on the job is bearings should not be too hot to hold your hand on for 5 seconds or more. That is supposedly about 40 to 45C or 110F or so. That is on a bearing that has been run for half an hour or so to get up to working temp.

But if your lathe is performing satisfactorily with cold-feeling bearings, no need to mess with it really. If you can take a 100 thou deep cut in steel with no tailstock support on a shortish job with no chatter, all is well. If it is chattering or giving other grief, then you might adjust the bearings.

Martin,

I gave some attention to that feed screw collar, tightened it up as much as possible without totally locking up the works. The backlash in the cross slide feed screw advance is now reduced to something around 10° of rotation of the handle. Relative to the previous amount when I first started these adjustments this feels more or less like 'immediate' response and is something I can absolutely live with.

If I really wanted to go crazy, there is a conversion kit offered by Vintage Tools in the Netherlands that replaces the end plate with a new one that uses thrust bearings. But it might be a bit of overkill for me. Vintage Tools Conversion Kit

This is of course correct for production standard S7s, however a number of users have fitted taper roller bearings to good effect which should give a more rigid bearing set up.

Edited By KWIL on 09/05/2022 10:51:11

That kit won't really remove backlash. You can tighten up the standard plain washer thrust bearings until they have zero clearance and achieve the same result. It just takes more time and skill to get the adjustment just right, and then with wear you have to do it all again occasionally. Any backlash due to wear on the feedscrew or its nut will still be there regardless of which thrust bearing you use. Usually the nut wears more than the screw so you could try replacing the nut next time Myford has them in stock.

Just to be pedantic you can get backlash on more than the screw and nut combination, the backlash on the end plate bracket bearing adds into the loss of motion. With the original plain bearing version, due to wear and inhearent tilt of the collar when the grub screw is tightened, there tends to be a spot that is tighter than other angular positions so to ensure free rotation the adjustment collar has to be set up to accommodate that spot. In other positions the collar will be looser than it need be and consequently the backlash will have a periodic error according to the angle of the handwheel.

I did the thrust washer mod on my lathe and set the leadscrew and collar up in a collet with the collar grub tightened and trued the bearing face. Similarly I remachined the inside bearing face of the endplate. This allowed the trust race to rotate freely at all positions with everything in contact so no backlash at all from that end, something you can't do with the plain bering setup without movement being stiff.

I doubt if any of that really matters but it pleased me.

regards Martin

Just another shoutout of thanks to all of you for the hints and suggestions. The spindle and cross slide adjustments have made a nice improvement in the lathe's performance.

Now that the spindle and cross slide have been seen to I also took the time to proceed with final leveling out of the lathe bed using the suggested method of cutting a test bar. A few tweaks to the bed screws brought that round right. I do note a bit of bed wear at the headstock end, but of course to be fair, this lathe is getting on 26 years of age and I'm by no means the first owner (second? third? fourth?). If I really want to drop some coin on this, that machine shop up in Holland does offer regrinding services, but I'm thinking that I'll first see how the lathe performs for me before taking any big (and doubtless expensive) decisions.