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Myford Super 7 binding spindle

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Carl10/07/2018 23:51:46
25 forum posts

Help...So i’ve adjusted the spindle/bearings on my Super 7 following the Myford instructions and the way described on the Myford Ltd website and still the spindle comes to s halt under power if anything other than a light force is put on it by the tail stock and i’m sure i’m not being heavy handed. It seems to be getting worse, any one got any ideas, have I missed something crucial to correct clearance ?

Thanks

Hopper11/07/2018 07:52:05
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5505 forum posts
137 photos

If you search this site, I'm sure there was an adjustment procedure by an ex-factory worker that was posted and reposted several times.

I can't find that one, so maybe I saw it someplace else? But this thread here https://www.model-engineer.co.uk/forums/postings.asp?th=107565&p=2  has some discussion that might help you.

Edited By Hopper on 11/07/2018 08:05:05

Martin Kyte11/07/2018 09:00:58
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2567 forum posts
45 photos

It's almost definitely moving backwards so the rear bearings are too far in.

This is the way to do it.

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)

Glyn Davies11/07/2018 09:20:03
131 forum posts
43 photos

As an additional precaution, I firstly slacken the bull wheel grub screw, then adjust the spindle bearings and then tighten the bull wheel screw to give the correct drive pulley end float.

Nick Taylor 211/07/2018 09:29:53
102 forum posts

Hi Carl,

It sounds like the preload on the rear bearings is incorrect, allowing the front bearing clearance to disappear when loaded.

Have the spindle and bearings been removed at all?

If you follow the procedure posted by Martin above (I’ve used it several times myself with great success) and you still have problems, then I would strip down the spindle. The three items that will affect the preload setting are the two rear bearings and the spacer between them. The key to the above procedure is the final wrap with a hammer on the crescent wrench! Skip that step and the bearing will bind.

If the bearings are very worn it may not be possible to load them adequately and if the spacer between them is either missing (more common than you think) or of incorrect thickness, then the bearings will not operate as intended. From memory the standard Myford spacer (part No A1991) is 20 thou thick.

Add to this the bearings could be the wrong way around (also more common than you think!).

Cheers,

Nick

Martin Kyte11/07/2018 11:14:47
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2567 forum posts
45 photos

One other point to note if you have ever changed a spindle, do ensure that the sleeve that abuts the shoulder on the spindle actually slides right up to the shoulder. My new (rebuilt) lathe from Myfords had this issue in that the last bit of the spindle just before the shoulder was tight on the sleeve. It was therefor possible to adjust the bearings as above and not force the sleeve fully in contact with the shoulder. The first time you put any decent axial load on the spindle from tailstock end the spacer moves and you lose all your correct clearances. (Does this make sense?). I solved my problem with a small amount of effort with an emery stick just working on the area a qurter of an inch before the shoulder. It was only a few tenths of a thou oversize but enough to generate the problem. Item 7 in the proceedure should in normal circumstances ensure that the spacer is against the shoulder.

regards Martin

Edited By Martin Kyte on 11/07/2018 11:15:06

Edited By Martin Kyte on 11/07/2018 11:15:44

Edited By Martin Kyte on 11/07/2018 11:16:22

HasBean11/07/2018 16:56:48
141 forum posts
32 photos

I went around the houses doing this only to find the motor to countershaft belt tension wasn't tight enough and the belt was slipping (not that I could see it though, had to touch the motor pulley to confirm).

Paul

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