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

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Ian P06/07/2011 18:07:07
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I have an Emco milling machine that is in really good unworn condition apart from the fit of the quill in the head casting. I am considering some sort of bush or sleeve but thought I would see if anyone could suggest a better method.
 
The quill is 48mm OD, about 100mm long and has a travel of 40mm. The cast iron head has a sawcut and clamp bolt but inexplicably (to me) is quite badly worn. I can easily put a 0.0025" feeler between the quill and the bore and it will slide in quite a long way. Tightening the clamp bolt obviously reduces the clearance but to clamp it firmly require more force on the bolt than feel right.
 
The OD of the quill looks unworn so I was thinking of boring the casting to take a sleeve of some sort. I could bore the casting in the lathe but making a sleeve with a 48mm bore and having only a relatively thin wall might not be too easy and then there is the problem of pressing it in place.
 
Another thought I had was reduce the ID of the casting by tinning it with soft solder, then boring it to the correct diameter. It sounds a bit crude but its not much different than white metal bearings, or is it? If I did this I would polish the quill OD to minimise wear of the soft surface.
 
Thsnk in advance for any suggestions
 
Ian
 
KWIL06/07/2011 18:54:29
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If you have the facility to bore the casting, why not do that and fit a thick walled liner and then bore that out to size, that way the thin bits are supported?
blowlamp06/07/2011 19:00:08
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Is the bore of the casting worn, or was it machined oversize - maybe even bored with the clamp bolt nipped down, thus making a tapered bore?
 
Anyway, if the bore is oversize but parallel, I'd be inclined to look at making a new quill rather than sleeving the casting. Fitting a sleeve could be hard to do and have it stay in position, if it's got to be split for the purpose of clamping.
 
 
Martin.
Dusty06/07/2011 20:23:23
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Before you embark on major work you need to ask yourself a number of questions.
The first of which is, does the milling machine work properly i.e. When in use does the quill rattle about when clamped.
Is there signs of wear in the bore in the vicinity of the split clamp.
What is the difference in size beween the bore and the quill.
The usual method of producing a split clamp is for the bore to be machined and then the clamp is split. Try measuring the width of the split above the clamp, then make a packer of this thickness with a hole through it to take the clamp bolt. This is then inserted into the clamp and the bolt is tightened. You can then either measure the bore or try the quill in the bore and see what result you get.
I would add that if something is not broken don't try to fix it.
The last question you should ask yourself is do I possess the skill to set up and machine the bore to the accuracy needed. You could make a very expensive mistake and end up with a milling machine that is inaccurate if not ruined.
JasonB06/07/2011 20:36:08
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I would have thought that any attempt to bore out the casting would risk running into the pinion as if its an FB2 then there is not a lot of room to play with.
 
If as Dusty says the clamp still holds the quill firm when tightened I can't see much point is doing anything.
 
J
 
 
Ian P06/07/2011 21:34:36
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Thanks for all the comments and advice so far.
 
My original posting did not give a lot of detail but I can add some more info that will explain my predicament.
 
When I used the machine after I first got it I was not happy with the surface finish (even with a single point fly cutter) which I put down to the bearings. Its a long story but I have now made a new spindle and rebuilt the quill with taper roller races and with the quill tightly clamped the finish quality and accuracy is really good. Unfortunately the action of tightening the clamp puts disturbs the alignment of the spindle with reference to the table. (I trammed the mill as near perfect as possible but may not have had the quill clamped, or in the same position.) I do not know for sure, but I think that in the clamped position the spindle is not parallel to the Z axis so to get the spindle correct means the shims will have to slightly tilt the column which will compromise other aspects of the alignment.
 
I could re-tram with the quill clamped but not being able to use the quill as a quill is going to limit the usage of the machine slightly.
 
The bore of the casting is slightly bell-mouthed, however, looking into the bore I can see that part of the bore that moves under the influence of the clamp bolt looks to be unworn, in other words, does not make contact with the quill until the clamp it tightened. With the bolt loose the lontitudinal sawcut is perfectly parallel so I assume that the casting has not distorted or 'opened' up.
 
Being made by Emco (in the 1960s) the engineering is of a high standard and as I mentioned earlier the table, ways, leadscrews etc are all in almost unworn condition. As I am getting to know the machine better I realise that at some time in its previous life thare have been some 'issues' with the spindle (it was bent!) so finding this problem with the quill does not surprise me, it just adds to the condition-anomoly mystery.
 
The head casting is a cast iron cube shape, machined on all faces, I think, and I could mount it on my Boxford cross slide and make a boring bar. I have never line bored anything before, but until last week I've never made a new spindle from scratch and toolpost ground the various tapers and bearing surfaces so I am willing to have a go at boring!
 
If I make a sleeve after the boring operation than the exact bored ID is not critical but I imagine that the sleeve wall would only be 1.5 to 2mm thick so making that wont be so easy. I looked online to see if any engine cylinder liners might be available in the right size but cannot find anything with a 48mm bore.
 
I'd better stop as this is already getting a bit long.
 
Ian
Ian P06/07/2011 21:38:50
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One other point, I think making a new quill body is going to be harder than modifying the hewad casting, apart from having to get the two bearing seats at opposite ends of a tube in perfect alignment, there is the problem of cutting the rack for the pinion.
 
Ian
elanman06/07/2011 22:07:59
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Ian,
A cylinder liner of 48 mm bore will give about 90cc so try looking for some of the 100cc Kart engine liners. They will be two strokes but normally come without the ports cut in.
You can also buy cast iron tube for making bearings etc.
Or you could try to get the existing quill plated or metal sprayed and ground back to size but this might cause a problem with the rack.
Cheers
John
blowlamp06/07/2011 22:08:55
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Posted by Ian P on 06/07/2011 21:38:50:
One other point, I think making a new quill body is going to be harder than modifying the hewad casting, apart from having to get the two bearing seats at opposite ends of a tube in perfect alignment, there is the problem of cutting the rack for the pinion.
 
Ian
 
You've done the hardest part in making the spindle, in my opinion
 
Clock your new quill in the four jaw and run the free end a fixed steady to machine each bearing seat, whilst maintaining alignment.
 
There is a few ways to do the rack depending on the equipment at your disposal.
 
You could use that between centres boring bar in the lathe to cut the teeth with a bought or home made fly-cutter (form tool).
 
You could use the milling machine itself - rough the teeth with a small end mill and finish with a suitably shaped D-bit type of cutter
 
You could use a shaping machine.
 
Get a friend to do it
 
 
Martin.
 
 
 
dcosta06/07/2011 22:39:32
496 forum posts
207 photos

Hello Ian.


Many years ago I built a column based on the Emco milling FB2, in a smaller scale, to fit on my Emco Compact 8 lathe.

So, the cylindrical column is made of steel thick walled pipe and the head is made of two cast aluminum blocks.
The quill is made of steel and is 61,6mm in diameter and its course is 45mm.
When I built the head, knowing that aluminum is soft and would be worn quickly, build a bronze sleeve from hollow tube with a thick shoulder at the bottom and set it unfinished inside, into the hole's head with a little Araldit. Then bored the hole for the quill in the bronze sleeve and used four screws to push the edge on the bottom against the aluminium block. The hole for the screws is made half in the aluminium half in the bronze so when boring to the diameter of the column the sleeve doesn't rotate. The last operation was to do the sawcut for the clamp.
For many years I do not use this small milling head, but while I used worked beautifully and still shows no signs of worn.


If I were You I would make the following:

1 - Make sure the rest of the hole ( the upper part) is parallel and has no execessive clearance.
2 – If it is parallel, make a sleeve with eight equal to the clamp parte of the head
and with diameter at least 4mm larger than the hole see, please,
http://www.model-engineer.co.uk/albums/member_photo.asp?a=14817&p=275512
3 – With a felt pen draw two crossed lines on the bottom face of the head block, one passing along the frontal sawcut. They are to be used in point 5.
4 – Mount the head block in the lathe carefully centered on the hole and bore the hole to the horizontal sawcut and to the diameter of the previously made sleeve.
5 – Fit the sleeve to the block head with some good Araldit and after the cure, using Your tools and skills make three holes (M5 by instance) in the place crossing the lines You draw in point 3. The place coinciding with the sawcut don't receive the screw.
6 – Tap the holes to M5 and apply adequate screws.
7 – Bore the bronze sleeve to the diameter of the quill
8 – Cut the bronze with a saw to form the clamping system.
9 – Clean the burrs in the sleeve inside.
10 – Try and mount the quill.

Or something along this lines.

Please forgive my poor use of Your language.

 
Hope this help
Dias Costa


Ian P06/07/2011 22:52:54
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2552 forum posts
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Posted by elanman on 06/07/2011 22:07:59:
Ian,
A cylinder liner of 48 mm bore will give about 90cc so try looking for some of the 100cc Kart engine liners. They will be two strokes but normally come without the ports cut in.
You can also buy cast iron tube for making bearings etc.
Or you could try to get the existing quill plated or metal sprayed and ground back to size but this might cause a problem with the rack.
Cheers
John
 
I had a quote recently from a UK spindle refurbishing company to build up and grind the bearings seats of the bent spindle, it is totally uneconomic!
To refurbish two journals was over £300. Grinding the taper (presumably the MT2 bore) was £160
 
As far as I can measure the quill OD is not worn, it would be nice if a 48.00mm ID sleeve existed but I doubt I will be that fortunate to find one.
 
Ian, another Elan (Lotus) man
Thats why I made the new spindle.
Ian P06/07/2011 23:01:34
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2552 forum posts
113 photos

Hello Ian.


Many years ago I built a column based on the Emco milling FB2, in a smaller scale, to fit on my Emco Compact 8 lathe.

So, the cylindrical column is made of steel thick walled pipe and the head is made of two cast aluminum blocks.
The quill is made of steel and is 61,6mm in diameter and its course is 45mm.
When I built the head, knowing that aluminum is soft and would be worn quickly, build a bronze sleeve from hollow tube with a thick shoulder at the bottom and set it unfinished inside, into the hole's head with a little Araldit. Then bored the hole for the quill in the bronze sleeve and used four screws to push the edge on the bottom against the aluminium block. The hole for the screws is made half in the aluminium half in the bronze so when boring to the diameter of the column the sleeve doesn't rotate. The last operation was to do the sawcut for the clamp.
For many years I do not use this small milling head, but while I used worked beautifully and still shows no signs of worn.


If I were You I would make the following:

1 - Make sure the rest of the hole ( the upper part) is parallel and has no execessive clearance.
2 – If it is parallel, make a sleeve with eight equal to the clamp parte of the head
and with diameter at least 4mm larger than the hole see, please,
http://www.model-engineer.co.uk/albums/member_photo.asp?a=14817&p=275512
3 – With a felt pen draw two crossed lines on the bottom face of the head block, one passing along the frontal sawcut. They are to be used in point 5.
4 – Mount the head block in the lathe carefully centered on the hole and bore the hole to the horizontal sawcut and to the diameter of the previously made sleeve.
5 – Fit the sleeve to the block head with some good Araldit and after the cure, using Your tools and skills make three holes (M5 by instance) in the place crossing the lines You draw in point 3. The place coinciding with the sawcut don't receive the screw.
6 – Tap the holes to M5 and apply adequate screws.
7 – Bore the bronze sleeve to the diameter of the quill
8 – Cut the bronze with a saw to form the clamping system.
9 – Clean the burrs in the sleeve inside.
10 – Try and mount the quill.

Or something along this lines.

Please forgive my poor use of Your language.

 
Hope this help
Dias Costa
 
 
Dias
 
Your language is fine, no need to apologise.
 
Your reply did make me realise that I only really need to sleeve the lower part of the casting. As long as I get the alignment of the bore coincident with the original hole then only the lower worn part needs the sleeve. Being shorter, probably only 60mm as against 100mm will make producing the sleeve much easier.
 
My machine is earlier then the FB2 and has the 4 speed geared head
 
Ian
ady07/07/2011 01:19:09
612 forum posts
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http://www.lathes.co.uk/emcomiller/index.html
"Even so, these units do not enjoy a reputation for long-term reliability and replacements are both difficult and expensive to obtain."
 
 
caveat emptor?
joegib07/07/2011 06:57:05
154 forum posts
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Posted by ady on 07/07/2011 01:19:09:
http://www.lathes.co.uk/emcomiller/index.html
"Even so, these units do not enjoy a reputation for long-term reliability and replacements are both difficult and expensive to obtain."
 
 
caveat emptor?
 
That comment you've quoted refers to the motor driving the machine, not to the machine as a whole.
 
Joe

Edited By joegib on 07/07/2011 06:57:45

Dusty07/07/2011 09:40:35
489 forum posts
9 photos
Ian
A couple of observations and then some questions. Looking at the FB2 and the machine I think you are talking about I notice that the FB2 has a transverse split above the 'clamp'. It appears that this was a scource of trouble in the past, I am not suprised that you think the force to clamp is high, you are trying to distort an almost solid casting. It might be worth considering running a slitting saw through as per the FB2.
I would not try throwing the column to get the head aligned, deal with the head if that is where the problem lays.
How much deviation do you get when clamping? If this is no more than a couple of thou I would live with it, remember these machines are only lightly built, the bigger and heavier the machine the greater the inherent accuracy.
Try re-tramming the head with everything nipped up and see what result you get.
Ian P07/07/2011 10:02:49
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Posted by Dusty on 07/07/2011 09:40:35:
Ian
A couple of observations and then some questions. Looking at the FB2 and the machine I think you are talking about I notice that the FB2 has a transverse split above the 'clamp'. It appears that this was a scource of trouble in the past, I am not suprised that you think the force to clamp is high, you are trying to distort an almost solid casting. It might be worth considering running a slitting saw through as per the FB2.
I would not try throwing the column to get the head aligned, deal with the head if that is where the problem lays.
How much deviation do you get when clamping? If this is no more than a couple of thou I would live with it, remember these machines are only lightly built, the bigger and heavier the machine the greater the inherent accuracy.
Try re-tramming the head with everything nipped up and see what result you get.
 
The machine I have, which is earlier than the FB2, does have the transverse slit at the top of the longtitudinal slit so its not the whole casting that has to be deformed.
I agree that I need to correct the errors at source rather than shimming the whole column. Whilst I could tram the mill with the quill clamped it then means that the quill is of little practical use.
Ian P07/07/2011 10:13:26
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Posted by blowlamp on 06/07/2011 19:00:08:
Is the bore of the casting worn, or was it machined oversize - maybe even bored with the clamp bolt nipped down, thus making a tapered bore?
 
Anyway, if the bore is oversize but parallel, I'd be inclined to look at making a new quill rather than sleeving the casting. Fitting a sleeve could be hard to do and have it stay in position, if it's got to be split for the purpose of clamping.
 
 
Martin.
 
Martin
 
You may have hit the nail on the head. It does appear that the bore was done with the clamp bolt already tightened but in reality it is highly unlikely. The machines are built to a high standard and I am sure it would have been checked and rejected at the time, so its just a bit of a mystery.
 
As I said the quill OD looks to have very little wear, whereas the bore is definately oversize so that is what I need to concentrate on.
 
Ian
 
jomac07/07/2011 10:48:11
113 forum posts

Blowlamp/Martin, Hi, before I got my small mill I started to make a tilting mill, why tilting, well, I did not have much of an idea on how to cut the rack for the Quill, so is it possible to elaborate on how to cut a rack in a solid or hollow bar, my lathe does not have a slotted top slide (next project !!!!) only a home made milling attatchment, I am also a bit vague on the measurement for a rack, I have cut spur gears, but more info on cutting racks would help a lot. If you cannot do a description on these posts, an article in MEW, might make Dave a bit happier.

PS, its cold down here in the Southern Highlands, with snow on the mountains only 5Ks away, its also raining, ergo, not much incentive to go into the work shop.

John H.

blowlamp07/07/2011 10:51:52
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Is the machine usable (to your satisfaction) with the quill clamp nipped down enough to remove play, but still allow free movement, i.e. does the bore return to a true circle?
 
If it does, then I'm thinking you could leave it in this semi-permanent state and make some other arrangement to lock the quill when you need to.
 
It would save a lot of work and could be used as a means of taking up any wear in the future.
 
 
Martin.
KMP07/07/2011 10:58:59
73 forum posts
2 photos
Ian Hi,
 
Two possible methods I feel. Firstly, bore out the lower part of the casting to parallel and concentric with the unworn top section. Then look into "electroless nickel plating", it is regularly done on tube inside walls and is deposited in reasonably well controlled thickness. Typical coatings would be 0.0025" or more if required. While fairly hard it can be machined back and is used to recover worn parts. Home kits used to be available but who knows these days with H&S as it is.
 
Second possibility is to add a "bearing plate" to the lower face of the housing. A simple cast iron plate maybe 0.75" thick might be bolted and dowelled to the lower casting surface and bored to match the top unworn section. While I guess it could be split to clamp I think converting the original to a wedge clamping action would be better if possible. Obviously you will loose quill movement equal to the thickness of plate you choose.
 
Haven't done either myself although we used hard chrome or nickel plating to recover many worn parts in the aviation industry. So just a couple of idle thoughts really.
 
Keith

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