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.

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

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.

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.

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

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