Best way to improve fit of main spindle quill in casting (long)

[Ian PParticipant @ianp]

Posted by blowlamp on 07/07/2011 11:52:33:

Posted by Ian P on 07/07/2011 11:21:28:

 

Its not really usable to my satisfaction, mainly because when the quill is clamped tight enough to remove play, it is not parallel to the Z axis column.

 

Ian

 

Is that looking from the front or the side and does the quill move freely?

I’m just trying to get feel for where the alignment errors are.

 

Martin.

Looking from the front I dont think there is a problem. The action of tightening the clamp has the effect of pushing the lower part of the quill towards the back of the machine, so tilting the spindle in a fore and aft direction.

 

Thre may be some sideways movement but as the head can be rotated its easier to compensate for.

 

Ian

 

Ian

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

High quality milling machines with round quill spindle arrangement always have means of adjusting the clearance of quill in housing . The most common arrangement is to have two or sometimes four split cotter adjusters internal to the quill housing . These consist of pairs of small opposed slightly tapered bronze blocks shaped to fit the quill and with a gap between them . Action of a pull up bolt draws the blocks together and at the same time seats them in the housing – thus providing a very fine adjustment of clearances .

[dcostaParticipant @dcosta]

Hello Ian.

Can You, please, identify Your Emco Milling machine in lathes.co.uk pages pictures?

It will help me better understanding of what we are talking about.

 

 

Best regards

Dias Costa

[Ian PParticipant @ianp]

Posted by Dias Costa on 07/07/2011 12:15:58:

Hello Ian.

Can You, please, identify Your Emco Milling machine in lathes.co.uk pages pictures?

It will help me better understanding of what we are talking about.

 

 

Best regards

Dias Costa

Dias

 

Its a very sensible suggestion and I should have sent a link earlier. At the end of the description there are photographs of a machine identical to mine.

 

Ian

http://www.lathes.co.uk/emcomiller/

[Clive HartlandParticipant @clivehartland94829]

Thats interesting, the head shown in the link is the same head fitted to a Maximat11 lathe.

We too had problems with being able to clamp the head tight.

When clamped and milling you could see the head working against the column.

In retrospect I think I would fit some hard nylon plugs backed up by skt drive grub screws in the clamping area. M8 sounds about right and they are easily replaced and adjusted.

Any comments on this method?

 

Clive

[Richard ParsonsParticipant @richardparsons61721]

What we are looking at here is a dead ringer for the Warco VHM mill. I have had one for some 18 years. I have only used the quill 3 times. My reason is the oil seepage I get every time I used the quill.

 

Dick

[dcostaParticipant @dcosta]

Hello Ian.

In the right image the horizontal sawcut appears to be in the lower part of the head block.

Is it so in Your milling machine?

If so, have measured the parallelism of the upper portion of the hole?

Best regards

Dias Costa

[DustyParticipant @dusty]

Ian

When you say the quill moves towards the column when applying the clamp are you sure that it is moving out of parallel with the column, with only 40mm of movement on the quill it is not easy to check. Try applying the clamp until you can still move the quill, then clock the the quill in the vertical plane and see what result you get. Ideally you need to clock over a much greater distance but the 40mm will give you some idea of the problem.

[KMPParticipant @kmp]

Hi Ian,

 

Could you bore out a 0.5-0.75″ wide groove in the quill housing casting to give some thickness for a lower bearing without taking all the strength out of the casting. If so then you can either cast in a Moglice bearing or even better cast a babbit bearing and machine back to the required size. I don’t know what the minimum thickness for a bearing would be but I guess anything over 0.060″ would be OK as there is no speed/heat involved in the quill movement. While it might be difficult to get the babbit to “stick” to the casting the annular form would provide support and stop the bearing moving with the quill. Although it is available in liquid form I’m not so sure about Moglice, it is either seen as the “best thing since sliced bread” or an impending disaster depending who you speak too, unfortunately I have no experience with it to guide you. That locking slit will compromise most possible repairs as to retain it any bearing material needs an element of spring, although babbit might survive small deformation I don’t think Moglice would.

 

Regards

 

Keith

[Ian PParticipant @ianp]

Posted by Dias Costa on 07/07/2011 16:34:10:

Hello Ian.

In the right image the horizontal sawcut appears to be in the lower part of the head block.

Is it so in Your milling machine?

If so, have measured the parallelism of the upper portion of the hole?

Best regards

Dias Costa

 

 

Yes the horizontal sawcut is towards the bottom of the bore, same as in the picture. I do not have anything I can accurately measure the upper part of the bore ID but it is definately worn to an unacceptable extent, so it needs bringing to the correct ID whether its parallel or not.

 

Ian

[blowlampParticipant @blowlamp]

Posted by Ian P on 07/07/2011 18:52:02:

 

 

Yes the horizontal sawcut is towards the bottom of the bore, same as in the picture. I do not have anything I can accurately measure the upper part of the bore ID but it is definately worn to an unacceptable extent, so it needs bringing to the correct ID whether its parallel or not.

 

Ian

 

Ian.

 

From what you say, it’s beginning to sound like it might have been inaccurately machined at the factory.

 

Before doing much else, it would seem sensible to establish for sure if it is worn or just oversized from new.

 

If it turns out that you’ve got a perfectly circular and parallel bore that is merely too big, you’re risking quite a lot by attempting to sleeve it and this is why I say have a look at making a new quill to fit.

At worst, it would only be a waste of your time and a little money if it didn’t work out.

 

What kind of bearing arrangement does it have – is it a needle-roller lower bearing by any chance?

 

 

 

Martin.

 

 

 

 

[Ian PParticipant @ianp]

I have not been checking parallelism at different points of the quill travel. I have been using an indicator mounted on the spindle (so that it ‘sweeps’ the table) to check that the spindle is dead vertical to the table.

 

I initially used this method to tram the spindle, then I used a flycutter and found one side cutting more than the other so I checked the tramming again and found it was out. On further investigation I found the poor fit of the quill in the head casting.

 

Ian

[Ian PParticipant @ianp]

Posted by blowlamp on 07/07/2011 19:38:07:

 

Ian.

 

From what you say, it’s beginning to sound like it might have been inaccurately machined at the factory.

 

Before doing much else, it would seem sensible to establish for sure if it is worn or just oversized from new.

 

If it turns out that you’ve got a perfectly circular and parallel bore that is merely too big, you’re risking quite a lot by attempting to sleeve it and this is why I say have a look at making a new quill to fit.

At worst, it would only be a waste of your time and a little money if it didn’t work out.

 

What kind of bearing arrangement does it have – is it a needle-roller lower bearing by any chance?

 

 

 

Martin.

 

Martin

 

I somehow doubt that the bore was originally manufactured oversize but having said that I am at a total loss to explain why the fit is so poor. The OD of the quill still has its original grinding marks visible and shows little signs of wear. Using my best digital callipers I can confirm that it is round and parallel but I dont have any calibrated standards to say what its exact diameter is, other than being very close to 48.97mm.

 

Whether the bore is just worn or whether it is perfectly parallel would not matter greatly if I made a new quill body because I could just make the OD suit the bore to a much better standard than it does now.

 

Regarding the spindle bearings, originally the bottom bearing was a parallel needle roller race than ran directly on the hardened spindle*. I have made a completely new spindle to replace it which uses a pair of taper roller races.

 

 

* The original spindle seems to be slightly bent! actually it a complete mystery because the bend is in the section between the bearings (30mm diameter and only about 60mm long) which is hollow because of the MT2 bore. The MT2 ER25 adapter is not bent but the taper part is slightly oval! All very strange….

 

[JohnFParticipant @johnf59703]

Dear Ian,

I reckon your machine must have had a rough life! I have an FB2 miller bought new some 25 years ago, it has been in constant profesional use ever since and has done 1000,s of hours of work.

I am now retired and It is still in daily use and as accurate as the day I bought it, its incredibly ridged for the size of machine. I worked for many years in industry on production jig boreing so am used to fine tolerances–the Emco will not give this performance but you can work to a two thou limit with ease, better if you are careful.

 

Regarding your problem I would suggest that if the spindle was bent some considerable force has been applied which may also have distorted the head casting? Boreing and inserting a liner may be the best solution and it might be worth asking your local engine re-conditioning shop if they will oblige with the boreing/lining, they will have the facility to bore and hone to suit your orininal quill to a high standard. Just a thought because clocking a horizontal bore for line boreing is always a problem due to “gravity droop” of the clock mechanism [worked for some time on a horizontal borer] Its not impossible but do take care if you go ahead to ensure you retain the original position in the casting.

Think I have waffled on enough so best of luck.

Regards John.

[Ian PParticipant @ianp]

Posted by Robin Woodward on 17/07/2011 09:54:37:

Hi All,

 

The mill described here with a 48mm Quill is the Emco “Mentor Mill”, it has 4 speeds as opposed to the 6 speeds of the FB2.

 

Surface finish on these machines can be a problem, single phase motors do not run that smooth, and gear transmissions do not help the case. That is why on the FB2 the gears are shaved for high precision and Emco fitted a flywheel on the motor spindle to damp out cyclic variation. The FB2 also has a pumped oil lubrication as opposed to grease on the Mentor Mill

 

The tapered bore is undoubtedly due to the single sided clamp, this will have “Sprung” out wards when the slit was put in. Being single sided and with enormous cross-section it would be very difficult to lock up, that is why the FB2 has the slit all across as Dusty suggests.

 

One thing Emco recommend is that all elements of the machines that are not being moved should be locked for maximum rigidity.

 

If you are hell bent on rectifying a fault that does exist from new, I know I had one new, then please the route to go is oversize quill in a slightly oversize bore. Sleeving in auto mobile engines is only done once all the oversize pistons have been used up

 

Rob

 

 

Robin

 

With the quill clamped I get an excellent surface finish probably because of the modifications I have made.

 

My 4 speed Mentor came fitted with a motor flywheel although I find it hard to see how it can reduce cyclic speed variations at the spindle nose especially as the flywheel is not rigidly coupled to the motor shaft. As you probably know the standard motor is wound for three phase so I have ditched the capacitor and run mine off a VFD.

 

I think the improvment in surface finish is because I have made a new spindle that uses taper roller races, The original bottom bearing (regardless of how good a condition it is) must have some sideways movement. As JS aptly described it earlier, its a rubbish design!

 

Using a 50mm radius flycutter with a (very sharp tipped cutter) the surface finish on aluminium is excellent with no evidence of any gearing related effects so I’m happy.

 

The oversize bore in my case is not caused by the casting opening up. The original slot looks to have been cut with a 3mm cutter and with the bolt loose, a 3mm thick feeler is gripped nicely. The bottom end of the bore has nearly 0.1mm of wear but there is also quite a lot of play further up the bore, harder to measure but its about 0.05mm. (0.003″ & 0.0025″) The body of the quill has very minimal wear and is also quite parallel so I dont want to make a new oversize one.

 

My plan is to sleeve the lower portion of the bore, (the section that always contains the quill) that way the upper, less worn part of the bore is retained as a reference for aligning the casting when setting it up. In any event if I get a good fit after sleeving the quill wont even come into contact with that part of the bore.

 

The only hold up at the moment is sourcing a suitable bit of seamless tubing to make the sleeve out of.

[Ian PParticipant @ianp]

Posted by Robin Woodward on 17/07/2011 12:34:04:

Hi all,

 

Obviously Ian the choice is yours at the end of the day, and you must choose what suits you best.

 

Having used Emco products for nearly 40 years I must disagree with the comment about the spindle bearings, I have every admiration for this design, simple but very effective, a high load carrying capacity in a small package, any play that might exist when the spindle is static is gone when the spindle becomes dynamic and the roller bearing runs on its film of oil. My machines have never given me the slightest problems as regards finish or accuracy.

 

Rob

 

If my machine had not had the bent spindle and quill problem I would be more than happy to have stuck with the standard setup and I am sure would not have any problem with surface finish or accuracy.

 

I too am a long time buyer and user of Emco equipment and have always considered to be manufactured to a high standard. Generally Emco’s designs are well thought out but this particular spindle is not one of their best designs and the lower needle roller race arrangement is a compromise. It does have the advantage of having a large enough ID to allow the Morse taper to be situated almost between the bearings so keeping cutter overhang very short but I am not convinced that the oil film has much relevance when it only exists in the line contact to the needle. I am no expert on tribology but with a conventional sleeve bearing the oil film is over a large surface area so I can sort of understand how the oil stays in place.

 

 

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Ian,

I have just been reading this thread out of curiousity … one never knows what useful hints will be found.

You obviously need to get the bore to the right size, and the quill running true, but the underlying problem of that poorly designed locking mechanism remains.

My suggestion would be to fill the “clamping slit” with a nice piece of gauge plate [dowelled and screwed in place] before you do anything else. Then correct the bore, by your method of choice. Then make a proper locking mechanism, along the lines of those preferred by the late/great Geo H. Thomas.
… This “split cotter” design is vastly superior to the “split clamp” arrangement and should be easy to fit by slightly modifying the existing hole.

MichaelG.

P.S. I have found this photograph of “Versatile Dividing Head” parts, which might be useful for reference.

http://staff.um.edu.mt/ccam1/tooldh2.jpg
http://staff.um.edu.mt/ccam1/tooldh2.jpg

[Ian PParticipant @ianp]

Posted by Michael Gilligan on 17/07/2011 14:56:35:
Ian,

I have just been reading this thread out of curiousity … one never knows what useful hints will be found.

You obviously need to get the bore to the right size, and the quill running true, but the underlying problem of that poorly designed locking mechanism remains.

My suggestion would be to fill the “clamping slit” with a nice piece of gauge plate [dowelled and screwed in place] before you do anything else. Then correct the bore, by your method of choice. Then make a proper locking mechanism, along the lines of those preferred by the late/great Geo H. Thomas.
… This “split cotter” design is vastly superior to the “split clamp” arrangement and should be easy to fit by slightly modifying the existing hole.

MichaelG.

P.S. I have found this photograph of “Versatile Dividing Head” parts, which might be useful for reference.

http://staff.um.edu.mt/ccam1/tooldh2.jpg
http://staff.um.edu.mt/ccam1/tooldh2.jpg

On this machine there is not enough room to use a split cotter type of clamp as the existing bolt hole position is too close to the outer edge of the casting so the cotter would break through the outer face and probably even then not be of a large enough diameter to intercept the quill.

 

On reflection, I’m not sure there is much to chose between the cotter and the split clamp. An ideal clamp would hold the quill without applying any force to it that would result in it moving to a different position. In reality either type of clamp mentioned will push the spindle sideways by an amount equal to the clearance.

 

Not having seen the article or book I dont know what GH Thomas suggested but I think the perfect clamp only exist as an ultimate goal, like perpetual motion!

 

Ian P

 

PS What did Geo Thomas

[Michael GilliganParticipant @michaelgilligan61133]

Ian,

You say:
On reflection, I”m not sure there is much to chose between the cotter and the split clamp. An ideal clamp would hold the quill without applying any force to it that would result in it moving to a different position. In reality either type of clamp mentioned will push the spindle sideways by an amount equal to the clearance.

I beg to differ; but of course it is your choice.

The Split Cotter effectively provides 3 point [or, hopefully, 3 line] clamping, which is inherently more stable.

I do, however, agree that the perfect clamp can only exist as an ultimate goal, like perpetual motion!

MichaelG.

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