Myford Spindle problems

[Don1966]

My Myford Super 7 has been giving me hints that it had problems. While cutting of metal with the parting tool the spindle would defect or push it self below the cutter. After taking the headstock spindle out and thrust bearings I found the problem. The two thrust bearings had to much play in them. So I ordered some from the UK. they should be in Monday. After I get them installed I will see if this cures the problem.
I have a few photos of what I am talking about.
The head stock with the spindle, pulley and gear removed.

The two thrust bearings


Don

[b.lindsey]

I hope the fix will be as simple as replacing the bearings Don. Sure beats what you went through with Grizzly!!  Keep us posted.

Bill

[Dave Otto]

Hi Don

I have been wondering what you have been up to?

These appear to be angular contact bearings? is it possible that they were not shimmed properly? It sure doesn't seem that a ball bearing would wear enough in a home shop to create that much slop.

Curious to see what you find out.


Dave

[Stuart]

Don

Make sure the middle outer shim has the gap at the top.

Make sure the spindle is well to the right , lock up thr two outer callers on the left.

Just nip up the clamp screw on the spindle adjuster so it can just move then tightn by hand to load up the bearings , tighten the clamp .

Now slack off the LH outer nut , tighten the RH until the spindle just nips up back off one slot , then fully tighten the LH one oil well

Run slowly check temps, build up the speed and keep a look out on the temp.

After a bit of run time test the end float with a dti repeat above if not nearly nil

Don't forget the the outer space need to be locked up before you preload

Yes I have been through it with my cony Myford put a non matched pair in cost me a new set at £170 they are bigger than yours the 7007 series

Take care a jobs a good in if you can still count to ten

Stuart

[Graham Meek]

Hi Don,

In the free state these bearings do have a lot of play even when new. The play is taken out when they are installed and correctly adjusted. There is a procedure to follow which is described in the Super 7 lathe manual. It is very easy to over tighten these bearings which will lead to premature failure. The play needs to be adjusted out of the bearings with the spindle well forward. This forward movement is achieved with the large castellated nuts. These move the the bearing assembly towards the change gears or away from them as the one nut is tightened and the other slackened.

As the bearing assembly moves this draws the front taper bearing on the mandrel / spindle in and out of the front bronze bearing thereby setting the running clearance. The bearing assembly is moved towards the changewheels as far is it will go until the spindle will no longer revolve, (gentle with the C spanner). The front castellated nut nearest the pulleys is un-screwed a measured 1/4" on the periphery of the nut and the castellated nut nearest the changewheels is locked up. This should provide the correct setting for the taper bearing as set at Myford's.

Do not forget to hold the oil wick down with a darning needle prior to assembly. Access to do this is via the grubscrew at about 8 o'clock when looking at the front of the headstock.

I hope I have not missed anything as it is 30+ years since I last did one of these, and the memory is not that good these days. If you are already aware of this procedure then sorry for trying to tell you something you already know, ( but it may help others in the future).

My best regards
Gray,

[Don1966]

Thanks guys for the help. The two bearings are indeed bad, one worst then the other. This problem has been on this lathe since I purchased it. I did the procedure as per the manual many times. What happens is after I preload the bearings and make the V bearing adjustment i still have to much movement back a forth. So when I install a piece between center and pushing with the tailstock the front bearing would seize up. So I had to back off on the adjustments. This would make the spindle to loose. I could push it back and forth by hand.

Don

[Stuart]

Don sounds like when you did the adjustment the outer races were not lock up solid.
they need to be to set the pre load ( remove any end play )

but if they are bad then nuff said

but please bear it in mind when the new ones are installed

spindle clear of front bearing , outer rear races locked up , adjust the pre load , then move the spindle back with the outer nuts as per the manual

on my big bore i needed a little more front bearing clearance than Gray said but that how mine is  you don't want it nipping up at speed else the chuck will unscrew  start a little slack then adjust it as you feel fit

Stuart

[Don1966]

Thanks Stuart I do believe that even with the spacer between the bearings that the two inter races were touching and there wasn't any preload left to do. There is that much slack in the bearings

Don

[Stuart]

Ok Don


Stuart

[steamer]

They may be angular contact, but not a matched pair, or a Universal grind.   

I'd love to see the adjustment procedure from the manual.   It would seem silly to not make these bearings a matched pair for DB mounting.  Then you wouldn't care about the preload on these as it's ground into them.    Tighten the nut till you grunt and you're done.


A cheap and dare I say cheerful solution is to put shims between the two bearings as single bearings are very much cheaper than matched pairs or DU grind.....but it would seem a false economy for a lathe.......to say nothing of a lot of painful work.

Dave

[Jo]

By special request 

Jo

[steamer]

Oh dear lord.    That's going to be a right royal pain....follow the procedure Don.....

Dave

[Graham Meek]

The presence of the spacer on the Myford is to allow the oil into the bearings as it is more of a "C" shape, (cut-out next to Zerk or oiler). I was going to ask Don if he has tried applying "blue" to the spindle taper and trying this in the bronze bearing to see if there is all round contact. For myself I suspect the bronze bearing may be oval which new bearings will not cure.

My best regards
Gray,

[steamer]

They may be angular contact, but not a matched pair, or a Universal grind.   

I'd love to see the adjustment procedure from the manual.   It would seem silly to not make these bearings a matched pair for DB mounting.  Then you wouldn't care about the preload on these as it's ground into them.    Tighten the nut till you grunt and you're done.


A cheap and dare I say cheerful solution is to put shims between the two bearings as single bearings are very much cheaper than matched pairs or DU grind.....but it would seem a false economy for a lathe.......to say nothing of a lot of painful work.

Dave

What I was getting at above is the DU grind pair is designed to have the inner and outer races touching on their faces.   The bearings are made such that when that happens, the balls become preloaded.     It' just about impossible to mess these up unless you get them dirty....but that is not the case here....so I would follow the instructions to the letter....as given in the Myford manual.     Disappointing......

The up side is the bearings are going to be about $20 a piece, instead of $400-500 a matched pair....still.......

[Don1966]

I took the bearing apart and didn't try real hard to pop it apart. The balls are oval shape and you can see the wear in the race. If you look close you can see a ring around the balls. You can also feel the odd shape.
Gray I have another V bushing if it is oval but I slipped the spindle into the bushing without the bearings and it is a good fit. If you tap it , it will lock in place so I would say thats good. The C spacer also helps to load the bearing. By the way the spacer is about .020" thick.
Some more pictures.




Don

Don