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Tom Senior M1 Vertical Head unit

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Brian Davies10/01/2012 13:14:50
27 forum posts
1 photos
Hi All
Does anyone have any exploded drawings of the vertical head on a Tom Senior M1 mill?
On mine the vertical spindle appears to be precessing and I want to dismantle it and have a look for the reason. A drawing would be very useful.
Many thanks
The Merry Miller10/01/2012 13:42:04
484 forum posts
97 photos
Brian, is this the head with the quill or without?
Len. P.

Steve Garnett11/01/2012 21:23:54
837 forum posts
27 photos
If you are talking about the knucklehead, I've currently got mine in bits, and can provide information/photographs, but no drawings. If it really is precessing, then just about the only thing capable of causing this is bearing wear, I would have thought. And also I would have thought that if it was doing this, it would be making quite a lot of noise about it?
Brian Davies12/01/2012 06:37:45
27 forum posts
1 photos
Hi Len and Steve
Many thanks for the replies. The head has no quill. I'm not sure I understand knucklehead, but if this implies the non-quill head then the answer is yes. I couple of photos would be much appreciated.
Steve Garnett12/01/2012 10:24:39
837 forum posts
27 photos
Well, if it's the one with no quill, then yes it's the one colloquially known as the 'knucklehead' - mainly because of what it looks like!
I'll get the bits out of the box later and take pictures of all of it. Hopefully later this year I'll get time to rebuild the whole mill, but I've been rather busy with work lately and haven't had anything like as much leisure time as I'd like.
There are a few pictures of M1 bits (including the output shaft from the aforementioned head) in one of my albums here - I'll put more in it later.
Brian Davies12/01/2012 15:40:23
27 forum posts
1 photos
Many thanks Steve, the pix make it look quite straight forward. I reckon I'll go ahead and take it to pieces and see what might be the problem.
I also have to remove the main shaft bearing ends to re-grease the bearings, they run quite warm even when on back gear speeds. On non-back gear the speed slows down appreciably very quickly.
The other item that is not covered in the manual I got from Tony Griffiths is the internal belt changing mechanism. In order to change speed by changing belt location internally you have to adjust the position of a lever that shortens the belt path, you can then swap the belt to a different pair of pulley grooves. That mechanism is not tight and does not retain its location such that the belt is always sloppy. There appears to be a pinch bolt that should tighten up the mechanism after having change the belt location. I cannot seem to get the pinch bolt any tighter. Also it is not clear how to apply oil to this same mechanism.
Have you any ideas please?
Steve Garnett13/01/2012 12:21:22
837 forum posts
27 photos
I've put more pictures in the album now, so you can see more clearly what's in there.
As for the belt changing mechanism, I can't tell you definitively at the moment because the whole thing is in a pile of bits in the 'storage' garage. But when I took it to bits, it was working fine - which leaves me to think that either your belt has stretched, or it had the wrong one fitted. One of the annoying things about the drive mechanism is, of course, that the belt can't be removed without taking the shafts out. What a lot of people do in this situation is to use segmented belts that you can join together around the drive shafts - and obviously you can adjust the number of segments you use until the tension is correct.
Steve Garnett13/01/2012 12:35:04
837 forum posts
27 photos
The other thing to note about the head is that the method of locating the output shaft, and the means of securing everything around it is weird. It relies on the end plates to hold it in place, and the screwed ring at the top does nothing more than clamp the drive gear to the shaft, as it's not keyed. Ultimately this means that the drive would slip rather than stall, which is probably a good thing. But the design means that preload has to be applied by shimming the shaft against the end plates, and so isn't adjustable. I have every intention of modifying mine so that the gear fixing is secured by one thread, and the preload is adjustable by another - although this will mean a modification to the output shaft mountings, and turning the bearings around. This isn't too easy to explain, and at some stage I'm going to do a drawing of it - mainly as a sanity check to make sure it's actually build-able and will work.
Thing is, if you are experiencing precession, then it may well be that the shaft has vertical movement - and if this happens, the bearings loosen up anyway - and this would almost certainly allow them to precess...
Brian Davies13/01/2012 17:37:46
27 forum posts
1 photos
Steve, All of that is more than useful grist to the mill (pun not intended!). Assuming I can get a camera all around it I will take pix as I go about everything associated with the overhaul as this may be of use to somebody else; but many thanks for your efforts.
Steve Garnett14/01/2012 10:08:40
837 forum posts
27 photos
I would certainly be intrigued by what you find, and yes it really is quite easy to get to bits, as you may well have found by now. If there are any original drawings of this head, then almost certainly the only source of them now would be Denford, as I believe that they took over Senior's assets. They certainly have some drawings, but I've not seen one for the knucklehead. Maybe worth asking them though...
Brian Davies24/01/2012 16:51:58
27 forum posts
1 photos
Steve, I have now made a start dismantling the knuckle head. Much prove very straight forward. Getting the driven shaft apart was not! It is not obvious that both top and bottom bearing, together with two spacing collars and the driven bevel gear are all removed from the top of the MT2 shaft. I have it in pieces now and when I have all the photos I will create an album.
I am going to replace both bearings on the driven shaft and both thrust races on the driving shaft. The latter are not in bad condition but it seems sensible whilst it is dismantled. Both bearings on the driven shaft are well clapped out, and is the source of the precession, both are quite loose and rock from side-to-side. I'm collecting a pair tomorrow from my local bearing emporium.
The two thrust races are a little strange. One set has washers 0.096" thick whilst the other washers are only 0.085" thick. The thinner pair appear to have been on a surface grinder so I can assume that they have been machined to provide the correct end float. However the securing nut is of the locking type and I can see no reason for such a delicate fitting.
geoff taylor03/04/2012 20:20:16
3 forum posts

Hope this thread is still valid and being read. I am trying to strip the vertical head of my M1 down and have got everything out with the exception of the output shaft. By the looks of the photos it should drift out towards the bottom, but it does not want to shift and I dont wish to tap it any harder for fear of wrecking the bearings.

Can anyone give me some advice please on what I am missing.

All help very gratefully received



Brian Davies04/04/2012 16:13:57
27 forum posts
1 photos

Hi Geoff

I Can help here as I have had mine completely to pieces. The driven shaft coms out through the top not the bottom. You have to remove the driving shaft first only then will the bottom bearing pass right through.

I used a piece of brass rod as a drift. I supported the body of the head in the vice and then wacked the brass drift with a big hammer.

To clarify my last message, I used brand new thrust races and both were identical. I did not find it necessary to reduce the thickness of one set as per the pair I removed.

I got the new bearings from Red Hill Bearing in Handcross West Sussex, they cost somewhere around £120, this did include some Rocol bearing grease though.

If you need any further info please let me know.



geoff taylor04/04/2012 20:44:04
3 forum posts

Thanks Brian, one good sharp blow on the bottom end with a nylon mallet had it out. The outer race of the bottom thrust bearing stayed in, whch now looks to tap out downwards, as thats up against a shoulder in the casting.

It is a strange arangement as in one of the previous posts. The bearings look and feel OK, just a chance to clean and inspect, remove the old grease and of course re-paint the head. I assume when refitting the top bearing is driven in as far as the top plate will push it, and thats it.

The whole machine has been stripped to the last nut and bold etc, cleaned, completely resprayed and is now 80% rebuilt., following thirty years of being in school doing not very much.

All i have found so far is the thrust bearings on the ends of the leadscrews have been shot.

Thanks for the help and advice, really appreciated.

Regards, Geoff

Brian Davies05/04/2012 08:12:15
27 forum posts
1 photos

Great stuff Geoff, good to hear that it worked out. Yes press the whole lot in from the top as far as it will go. Mine worked so well afterwards. What is strange about mine is why the bearings were so bad as to cause the precession that they did! My machine also came from a school and clearly had been little used. There were so many protactive shields on the beast that as it stood you simply couldn't have used it! The first thing I did was to remove the lot and sure have been pleased with the result. Used as a horizontal mill, with two identical side and face cutters I made a series of T nuts for the main slide.

Currently I'm in the process of fitting digital readouts on all three slides. I have the electronics built, but not tested and the scales have been fitted complete with swarf/fluid shields. This should make life easier.

All the best


Steve Garnett05/04/2012 09:47:14
837 forum posts
27 photos

Posted by Brian Davies on 05/04/2012 08:12:15:

What is strange about mine is why the bearings were so bad as to cause the precession that they did!

Almost certainly that would be because there is, in the original design, no way to set the preload accurately - you have to shim the ends and then refit, possibly several times. If you don't do this, the balls in the lower bearing don't centre up properly. What makes this even worse is, of course, that it's a single bearing. You can probably tell how far out it is by measuring how far oversize the cut is on a single shallow slot.

When I get round to it, I'm going to modify mine so that it can be accurately preloaded. I have an embryonic plan for doing this, but it will constitute a major modification to the output shaft, and I'm still considering one or two aspects of it. In fact the whole mill refurb is on the back burner at present - rather more pressing matters to deal with.

Oh, and I know what you mean about the guards. Mine didn't come from a school, but all the guards were in a box anyway. And they're staying in it.

Brian Davies06/04/2012 08:53:24
27 forum posts
1 photos

I agree about the preload, I have been considering just this aspect and I have been seriously considering the possibility of putting in roller bearing top and bottom, this could negate the need for preload perhaps?



Steve Garnett06/04/2012 12:16:40
837 forum posts
27 photos

If you used roller bearings, you would possibly reduce the radial play somewhat, but you'd still have axial play problems - and that might be even worse! What the preload does (and which is why it's still the correct way to do it) is to optimise both radial and axial spindle play at the same time.

The real issue with this particular design is that there's no reference within the bored casting itself for the spindle position, other than the end plates. The very nice adjuster at the top of it, which looks ideal for preload adjustments, doesn't do a complete job - it only preloads the top bearing, whilst locking the bevel gear in position. The bottom bearing has no reference other than the bottom plate - and that's all wrong. It needs a solid reference above it, not below it!

So the current plan is to use the adjuster to preload both bearings, and the way to achieve that is to fit a sleeve inside the casting, with a cutout in the side of it for the driving gear. The sleeve fits between the top and bottom bearings (arranged appropriately) and when you do up the adjuster above the top bearing, it pulls the two bearings together and into alignment. This means of course that you have to find an alternative way of making sure that the bevel gear is locked in place, because the adjuster's final position is limited by the lower bearing position and won't lock it any more - but I don't think that this will be particularly complicated to arrange. So just to be clear about this - both bearings are now referenced against a fixed sleeve, and not the covers!

I get the impression that this may be more like what was originally intended for this head, quite frankly - the existing compromise for the most important bearing just seems wrong. Unfortunately there's no way you could fit a second bearing easily on the lower part of the spindle, because the bevel drive gear gets in the way, and there doesn't appear to be any way around that limitation - which is a shame.

But the revised arrangement should be quite good though - it will mean that you can reassemble the head and run it with the top cover removed, as it won't be retaining the spindle any more - and it will give you easy access to the adjuster.

Anyway, I hope that this is some food for thought, at least.

Regds, Steve

tony bastick08/07/2012 15:47:40
15 forum posts

Hi, just been reading these threads as i was about to do an overhaul on my vert head to replace the bearings. Do i understand from the coments so far that we have a ball berring at the top and a thrust bearing on the vertical driven shaft? Also what is precession? Thanks Tony.

Brian Davies08/07/2012 16:06:05
27 forum posts
1 photos

Hi Tony. There are two ball races on the vertical shaft, one at the top and one at the bottom. To remove these you first have to remove the horizontal driving shaft, that comes out the back. Only then can you knock out the vertical shaft upwards.

There are some photos that were posted by Steve Garrett, see the thrid post on this thread.

Precession is where the shaft wobbles as well as rotating, the earth has this same wobble. The result is that the cutter will cut a larger bite than if it were stable. The reason for my precession was that the bottom bearing on the vertical shaft has lots of play in it.



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