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Super 7 Headstock Set Up

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Alan Wood 419/02/2015 20:56:02
152 forum posts
6 photos

My Super 7 Large Bore began to make 'crunching/ grinding' noises from the headstock area. These were random and did not seem based on loading.

After some investigation with a 'stick to the ear' I figured that the angular bearings might need attention.

Taking the bull by the horns I stripped the shaft assembly down. This is straightforward.

Chuck off.

Remove the grub screw that is under the spindle and stick a large darning needle into the hole to spear the wick.

Undo the set screw in the main gear wheel.

Drop the tension on the drive belt.

Take off the thread protecting end bush.

Loosen the set screw in the end collar and take the collar off.

Protect the end of the shaft with a block of wood and tap the shaft free.

Gently pull the shaft out of the bronze front bearing while catching everything that slides off it in the process (including the two Woodruff keys before they drop down into the works).

Undo and remove the two castellated bearing retainers in the casting with a C spanner.

Push the bearings out.

Doddle, 10 minute job.

The front bronze bearing was clean with no scratches visible - relief.

The rear bearings didn't seem that bad but there was lots of crud in them and if I spun them stuck on my fingers they did rattle a bit. Sifting through the debris in the bowl after cleaning didn't reveal any solid foreign bodies.

The original bearings were NSK type 7007A which didn't seem to exist anymore. A call to Myford got me two new bearings by IBC with the same 7007 code. Given I had it all in bits I also ordered a new wick to oil the front bronze sleeve bearing. These tend to harden over time so worth doing.

So I now had all the bits to rebuild it.

First problem was the new wick was oversize for the feed hole against the shaft. Some shaving with a scalpel trimmed it to size.

A call to Myford told me that the new bearings had to go in with the thinest side of the outer ring, outer most - i.e, the front one with this side to be facing the chuck and the rear one facing away from the chuck. This meant for the bearings I had in front of me, the inscription sides on the bearings were facing each other. Sandwiched between them is the spacer washer. This has to go in with the gap in it, at 12 o'clock where the oil can feed down into it from the oil nipple on the bearing housing.

Now have you ever tried to make sense of the re-building as described in the Myford official manual ?

I was apprehensive to say the least as it made no sense. The new bearings were very tight on the shaft which worried me but I did what I thought was right per the manual and after oiling up well, switched on. (Don't forget to put the drive belt back on the shaft ...)

Not a good sound ensued. Probably worse than it was before. Really crunchy. Expletives.

Switched off and had a brew (or two). Scrap paper and pencil time. It took a while to dawn that there are two things going on.

The first thing is that all the elements on the shaft up to the 'spindle thrust shoulder' (5 in Fig 34) have to be squeezed together by the end rotating collar (4). To say you can do this with hand tightening is not practical. You need a spanner with two prongs on it to match the holes in the end collar. You can buy these from Myford but needs must and I made a crude one to do the job. Before you begin to tighten this up, loosen off the two castellated nuts sandwiching the bearings so the bearings are free to pick their own position inside the casting shell.

Once all the components are tight on the shaft you can now adjust the right hand side castellated nut to pull the front cone into the bronze bearing bush. Tighten this until the cone sticks and then back off by the specified 15 degrees so the cone is then free to move again. I fiddled with this a few times to make sure it wasn't binding in any way. Tighten up the left hand castellated bush to lock the bearings in place.

Switched on and what a difference, almost sewing machine quiet.

Given the experience I would now think that the old bearings were probably OK and had not been set up properly by the previous owner.

OK, you might say this is all obvious but I could not find anything on the Net to explain this is in simple terms and maybe I have still not fully understood but it is a different machine now.

Or have I made a fundamental mistake that someone is about to tell me about ?

Alan

Harry Wilkes19/02/2015 21:03:46
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987 forum posts
63 photos

Thanks for an informative post !

H

Cabeng20/02/2015 00:30:47
86 forum posts
59 photos

You may already be aware of this Alan, my apologies if you do, but over-oiling the angular contact bearings on either S7 or big bore lathes can cause them to make 'orrible noises as the races thrash around in the excess oil. Dificult to describe a noise, what you describe might fit the bill. But then again, it might not!

It's not a sealed system so they will drain eventually. Running at low speed will help to speed up the draining process.

Alan Wood 420/02/2015 10:10:58
152 forum posts
6 photos

Hi Cabeng

Thanks for the useful comment. I am new to the hobby so I am trying to absorb and understand as much as possible.

I don't think this was the issue as it had been going on for a while with the old bearings with no heavy oiling. I had tried various adjustments with the new bearings before I went back to first principles in understanding what I now believe is going on. I guess had I understood the process a bit better I would have played more with the settings with the old ones still in place. It might have saved me a few quid and reduced my down time.

I still don't fully understand the 'loading' expression.

If, as I have now, all the components on the sleeve are held in place tightly by the end bush then all the adjustment of the sleeve taper position in the bronze front bearing is down to moving (in effect) the outer rings of the bearings within the casting using the castellated nuts. This is putting a sideways pressure on the outer ring of the bearing nearest the chuck (right hand one). The left hand one is then being tightened up against the right hand one with the split circumference washer between them to support it. As the sleeve is adjusted out of the bronze front bearing, the pressure on the outer ring of the right hand bearing reduces as it is not having to 'pull so hard'.

The Myford handbook implies the loading comes from the end sleeve adjustment but I guess this might assume the bearings have not been swapped and are still in place from the prior assembly ?

Still a lot to learn but it still sounds lovely this morning and I can get on with cutting metal again without twitching every time I had heard the graunching noise.

Further comments appreciated.

Alan

Cabeng20/02/2015 11:16:23
86 forum posts
59 photos

Alan: All that 'loading' means is that the inner races have to be moved together so that the balls are in contact with the outer races, bearing properly on the outer tracks. Then to keep them there under varying conditions of load and temperature, they have to be clamped together a little bit tighter still - pre-load. But not too tight, or the bearings will suffer excessive wear and possible damage.

Do you have the manual for the lathe?

Whereabouts are you located?


Ady120/02/2015 11:23:08
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3871 forum posts
522 photos

I've been meaning to do a write up in here of my Drummond/Myford M series for a while now I've finally (i believe) sussed it out

The best system I found was to preload the spindle with a workpiece in the spindle nose collet chuck and then hold the spindle in its preloaded position using the tailstock with a live centre

Once everything was loosened up the tailstock preloads the back of the spindle against the rear thrust bearing and the live centre allows the spindle to revolve freely by hand, even with loose unadjusted headstock bearings

Then you do your headstock bearings and the spindle cannot move out of position because the live tailstock is supporting it

This has worked so well that the first time I did it the oil simply sat in the oilers and wouldn't go into the bearings, the tolerances and fit are so good that I now need to use finger pressure to "pump" the oil in

(Tightness required setting the bearing was low to moderate. If you tighten up too much the spindle will be locked in the solid bearing when it cools down and you return the next day)

So try the tailstock live centre system if you want really good accuracy for your particular headstock bearings

edit

btw I'm jealous of your big bore spindle, it's the only thing a Drummond lacks

 

Edited By Ady1 on 20/02/2015 11:32:35

Cabeng20/02/2015 11:40:02
86 forum posts
59 photos

Forgot to mention:

1) The NSK bearings are still available, but I think the only ones they do now are higher spec. versions than originally fitted . My lathe has been wearing NSK7007A5TRDULP3 tail bearings for about 2 years.

2) Myford did introduce a revised front bearing adjustment procedure at some time, but as far as I know it never found its way into the manual:

myford spindle adjustment.jpg

Note the bit about the scribed line, which refers to re-adjustment of the original bearings. From my experience of fitting new bearings to my S7 and Connoisseur machines, it won't be far out with replacements.

Alan Wood 420/02/2015 11:47:50
152 forum posts
6 photos

Thanks both of you for this.

Cabeng - OK on pre-loading, the mists begin to clear. I am a retired radio engineer with metalworking tendancies so can help you on intermodulation and blocking should you ever need to know ..... .I'm located near Newbury and I have copies of the handbook.

Ady - I think I get what you are saying and like the concept. I don't have a collet set for the spindle as yet, only a 3 jaw but the same should work. Will have a play and let you know. The S7 is 2001 vintage and very clean. Got it from Myford Lathes in Wiltshire. I also got a VMB and a BCA from him.

Alan

Alan Wood 420/02/2015 12:31:11
152 forum posts
6 photos

Hi Ady

I have tried the dynamic technique and think it has merit. It makes me feel a bit more comfortable.

But ... seeing your later post with the image of the instructions, the scribed line on my shaft is a long way adrift on the collar split, like 180 degrees. I saw this line and assumed it was to tell me where the keyway was on the shaft.

My good feeling now dissipating ....

Alan

CotswoldsPhil20/02/2015 13:23:43
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196 forum posts
112 photos

Allan

From your first post......

The first thing is that all the elements on the shaft up to the 'spindle thrust shoulder' (5 in Fig 34) have to be squeezed together by the end rotating collar (4). To say you can do this with hand tightening is not practical. You need a spanner with two prongs on it to match the holes in the end collar. You can buy these from Myford but needs must and I made a crude one to do the job. Before you begin to tighten this up, loosen off the two castellated nuts sandwiching the bearings so the bearings are free to pick their own position inside the casting shell.

Once all the components are tight on the shaft you can now adjust the right hand side castellated nut to pull the front cone into the bronze bearing bush....

 

I replaced the bearings on my S7 last year, so from my experience of deciphering the instructions, I think you are over-tightening the split adjusting collar.  It should be hand tight only, no tools required to set the pre-load apart from an allen key to lock it in place. I believe the large split spacer is not there to set the pre-load, but to allow space for the pre-load and allow the outers to be clamped together to set the front cone bearing clearance, and for passage of oil!

Regards

Phil H

Edited By CotswoldsPhil on 20/02/2015 13:44:46

Alan Wood 420/02/2015 13:51:39
152 forum posts
6 photos

Hi Phil

Been dwelling on this bit.

Initially I did the end collar up by hand but perhaps because the new bearings were so tight on the shaft I did not realise that the various components were gapping on the shaft. By making and using the tool I have 'shuffled' everything along the shaft but perhaps now overdone it ?

Having gravitated to the point where it has now come to rest, I can hand tighten and loosen but it does not align with the mark on the shaft. This is my slight worry.

Everything else seems fine.

Alan

Lambton20/02/2015 14:03:46
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694 forum posts
2 photos

I echo Cebeng's comment about noise from the angular contact bearings if they are over-oiled. I replaced the angular contact bearings on my S7 recently with new SKF ones. I noticed the old bearings were still OK but had some dried oil caked on them in places making me suspect their lubrication. I tested the oil nipple with my old Tecalamit oil gun and found it would not push any oil worth speaking about through the nipple. I purchased a new "leak-free" oil gun to lubricate then new bearings. The new oil gun pushed the oil through the nipple with gusto (despite the fact the gun leaked when left but that is another story!)

On reassembling the lathe mandrel following Myford's instructions I gave the new bearings a good old go with the oil gun only to find the noise described by Cebeng - most disappointing. As Cebeng says it eventually drained through and every thing was OK. I have now replaced to original Myford oil nipple with a gravity type having a hinged lid - similar style to the front headstock bearing and not put a few drops of oil in each time I use the lathe. Using the oil gun is impossible to gauge how much oil has been pumped into the bearing which obviously does not like too much. The noise is probably due to the bearing cage wising round rather than from the ball bearings themselves.

KWIL20/02/2015 14:35:52
3309 forum posts
63 photos

Alan,

I still use the oil gun approach but only one quick dab when needed. As Cabeng says you only need a small amount of oil, as long as you do not allow the bearings to drain out completely.

More recently I have moved over to using taper roller bearings rather than angular contact ball races, but this requires some modifications to the castellated clamp nuts and spacers but for me a quiet running stiffer bearing arrangement.

Edited By KWIL on 20/02/2015 14:41:13

CotswoldsPhil20/02/2015 14:53:58
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196 forum posts
112 photos

Hi Allan,

I've just taken a look at the mark on the mandrel and in my case (with new bearings) it's within the width of the slot in the collar.

Hi Lambton and Kwil

Come to think about it I heard a couple of rattles after replacing the bearings, plenty of oil! but since then, all quiet, apart from the ever present swish.

I tested the oiler before screwing in the rear castellated nut, and all appeared to work. I like the idea of the gravity oiler.

Regards

Phil H

john fletcher 120/02/2015 15:50:12
624 forum posts

RS components have the correct bearings and are almost half the price of other suppliers. You don't need an account either, phone head office and arrange to collect from local branch or local branch might even have them on stock, I did.Ted

Ady121/02/2015 01:24:07
avatar
3871 forum posts
522 photos

Your tailstock may have sufficient reach and you can use a live centre directly into the bore although in your big-bore case you would need a live centre for doing tubing

The main thing is that the spindle stays put, and can still revolve by hand, while you do your bearing tweaks

headstock1.jpg

Ady121/02/2015 01:48:53
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3871 forum posts
522 photos

Something I have found useful for my big castellated nuts is those curved jaw mole grips, the 8 inch versions

They fit nicely on a drummond in the absence of a proper spanner

I'm only mentioning this because on a well known site the castellated nuts of a lathe I was looking at had either been chewed by a pit bull terrier or the guy had been using a hammer and chisel to tighten and slacken his spindle bearings

Chris Trice21/02/2015 02:52:03
avatar
1362 forum posts
9 photos

I carried out Ken's (KWIL) modification to taper roller bearings on my Super 7 and can vouch for the improvement. I'm still not sure I understand why over oiled angular contact bearings should make such a racket? Hydraulic locks or something?

Cabeng21/02/2015 10:08:33
86 forum posts
59 photos

I don't know the answer Chris, but it's a wierd noise, as if the balls were bumping into each other. Once heard, never forgotten.

I've seen this reference to KWIL's taper bearing mod a number of times. What's the advantage, and what's involved?

Cabeng21/02/2015 10:23:32
86 forum posts
59 photos

Alan & Ady1: Adjusting the spindle is a simple two-step job: 1) Set the pre-load on the angular contact bearings, which also pulls the outer races into contact with the spacing/oiler collar, and clamps the bearing ssembly against the step on the spindle, then 2) shift the bearings and the now attached spindle about to adjust clearance in the front taper bearing. The procedure described by Myford has been applied to countless lathes by countless model engineers over the centuries, and is well proven.

I can see the logic behind Ady1's procedure, but why depart from a method that is well-established and proven to work?

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