Unimat 3 Vertical Head Quill

[Kiwi BlokeParticipant @kiwibloke62605]

Hi Folks,

I've recently acquired a very-little-used Unimat 3, with vertical milling head. Not sure why, exactly, but there you go…

Bizzarely, there is a few thou axial free movement of the spindle within the vertical head's quill, rendering it more-or-less useless for milling. The manual and spare parts diagrams show the quill as an assembled unit, with no internal spares available. I can't see how the quill unit is assembled. There's a collar on the spindle shaft, at the pulley end, but no evidence of an expected thread, nor pin-spanner holes, nor any obvious means of removing the collar to get at the innards – assuming that removing the collar is what is needed.

Anyone got any ideas?

[Kiwi BlokeParticipant @kiwibloke62605]

[John OlsenParticipant @johnolsen79199]

If I remember correctly, inside there are two ordinary deep groove bearings, possibly with a spacer in between, and a retaining collar pressed on the top. So you should be able to press the spindle out and replace the bearings and then press it all back together. I did wonder if it might be possible to replace the bearings with something a bit better, but never did find anything good that would fit.

I still use the little lathe a bit for tiny work, but find that since I have a big mill, any milling work is just as easily done on that. Even small stuff!

Another Kiwi bloke…

[Kiwi BlokeParticipant @kiwibloke62605]

Thanks. Strange way to assemble, don't you think? I wonder how bearing pre-load was supposed to be controlled. So, supporting the quill's nose end and pressing out the spindle might be the way to go (munting the bearings on the way)? Sounds a bit too close to the well-known Rip, Sh*t or Bust technique for comfort…

[John OlsenParticipant @johnolsen79199]

Yes, it struck me as a little on the crude side. It also bothered me that on assembly you have to push the bearings in, which can't be the best for them. Of course with the gear I have now I could probably improve things, maybe screwcut on the inside so that the preload could be controlled by screwing in a retaining ring. Still, within their limits the little machines will do great work. When I got mine 34 years back my brother in law, a fitter and turner, was a bit scathing about the tiny machine. Six months later when I showed him my Stuart 10V, made from the set of castings that came with the lathe, he was much more impressed.

Of course the 10V is about the biggest that you can do with one. I have done most of a double 10 on one too, including milling out the crankshaft from a solid blank. The shaft that came with the double ten castings had a hard spot at the weld in the middle that defied even carbide tools, so I started again. I milled away most of the material with the shaft supported between the lathe centres.

Just back from a run of our Newcomen engine here in Auckland.

John

[Kiwi BlokeParticipant @kiwibloke62605]

Well, I can now answer my own question. Perhaps others are wondering, or experiencing the same problem.

The answer was in several threads on the the appropriate Yahoo group. I'd not liked Yahoo's privacy policy, so hadn't signed up, and had assumed that I couldn't read submitted posts, so never looked. Doh! Also, Colin Usher's ME index revealed that a rebuild of the quill assembly, to incorporate ball bearings, had been described in ME in the past, complete with sketch of quill.

Apparently, the bearings are Oilite or bronze bushes, pressed into the quill housing. The collar at the pulley end of the shaft is pressed on. Not the most awe-inspiring design… The shaft can be removed by pressing out from the pulley end. However, rather than resort to DRASTIC ACTION, I tried moving the collar down the shaft a bit. Supporting the collar on a suitable length of tube, I scientifically walloped the spindle nose (with an interposed brass drift!) wiv a 'eavy 'ammer. Success! This gave me courage to apply the same treatment to another rattly quill. On this one, I couldn't have been scientific enough though, because the bearing went too tight. So, reversing the set-up and applying science to the spindle's other end, I was rewarded with a sweetly-running, end-float-free spindle. So, folks, it works, with 100% success on my sample of 2…

OK, it isn't a definitive fix, and sounds more brutal than it really is, but it'll probably be good for a few years of gentle use – and can then be repeated, until the 'definitive' re-build is done.

Hope this helps someone.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Kiwi Bloke 1 on 08/05/2015 08:03:21:

… Apparently, the bearings are Oilite or bronze bushes, pressed into the quill housing. The collar at the pulley end of the shaft is pressed on. Not the most awe-inspiring design…

Hope this helps someone.

.

Always useful to know how things are designed

… Albeit disappointingly crude in this instance.

Thanks

MichaelG.

[Dan HookParticipant @danhook54007]

I had some free axial movement as well, and I fine-tuned it with a hammer at first, but then I decided to take it apart. The bushing closest to the spindle thread was slightly more worned than the top bushing, and since they have the same dimensions I decided to shift them. The mill runs a lot better now, but I sure would like to replace the bushings. In what issue was the rebuild of the quill described? What kind of bearings was used? Did they thread the top to get the preload? The only bearings I've found that would fit is F6802 (15x24x5 with 26mm flange) or 61802 (same dimensions but without flange). The bushings has ID 15, OD 20, depth 12 with a 25,5mm flange. The outer diameter of the quill is 32mm so boring it to 24mm would be possible.

[Kiwi BlokeParticipant @kiwibloke62605]

Hi Dan,

Sorry for delay – I haven't been paying attention…

The modification was written up in ME Vol. 176, No. 4008, p. 48-9 (5 Jan 1996) by Graham Nickson. Because the author couldn't find suitable-sized angular-contact bearings, he made a new spindle, of 9mm diameter, to fit commercial ball bearings (RHP 619/9, 20mm OD). An imperial thrust bearing was used at the top (RHP LT 3/8) and a home-made thrust bearing was used at the spindle nose end. These sat in the quill counter-bores. The bearing he made comprised silver steel races 25X9X1.0mm either side of a phos-bronze cage 2.5mm long, housing 12 X 3mm balls. Spindle nose and pulley ends were added. The pulley adaptor was threaded to the spindle, for pre-load setting, and locked by a radial grub screw. The axial bearings were separated by a tube spacer. The quill was not modified, as far as I can tell.

A letter a little while later, from someone who performed the modification to his machine, suggested that his machine was transformed.

Hope this helps.

It's a pity Emco dropped the ball this time.

Edited By Kiwi Bloke 1 on 01/11/2015 10:19:52

[Dan HookParticipant @danhook54007]

Thank You for a very informative and helpful post I don't have access to that issue of ME, but I think I understood quite clearly anyway. I does not feel right to modify the quill so making a new spindle is probably the way to go, but I think I'll try to use a commercial bearing instead if making my own. Provided I can find something that fits. Hopefully someone developed a bearing with suitable dimensions in the almost 20 years that passed. Again, thanks for taking your time to describe the modification!

[Michael GilliganParticipant @michaelgilligan61133]

You may get some inspiration from this amazing article by J.Malcolm Wild.

He sourced some very interesting bearings … but I have no idea if anything similar is avilable in a suitable size.

MichaelG.

[duncan webster 1Participant @duncanwebster1]

I've probably got a copy of the article in the attic if you're interested.

[Kiwi BlokeParticipant @kiwibloke62605]

Hah! Duncan's beaten me to it. I have a scanned .pdf of the article – just PM me if you'd like it.

My interest re-piqued (is that possible?), I ferreted around the 'net for possible bearings. I came across needle bearings with angular contact ball bearings assembled into the same, small-wall-thickness housing. Can't remember if a suitable size was available. I quickly lost interest, and had to lie down for a bit, after I saw the price…

I'd guess that a couple of the tiny needle thrust bearings, now easily available, might be suitable. I should have mentioned that the tube separating the ball bearings was fitted to the spindle, bearing on the inner tracks. If this were a really close fit on the spindle, it would restore some of the rigidity lost by having to make the spindle such a small diameter.

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

I am resurrecting this seven year old post because I have come across a video posted ten months ago on YouTube by a chap who shows how to disassemble the Unimat 3 milling head which btw is, according to Tony Griffiths of lathes.co.uk, the same one used in the Emco Compact 5 and Compact 8.

The video is brief, clear, to the point but more than anything else, the method works. 8^)

In my case, the spindle (from a ca. 1980 milling head) has axial play and needs new bushings but it was really stuck and would simply not budge.

So I dowsed the pulley end with WD-40 and left it a few hours, then tried coaxing the spindle with a bearing extractor and after applying a force till I could apply no more, it finally buged ~ 2mm but then refused to go on.

Some heat gun magic and more bearing extractor force followed by a seemingly endless number rapid (machine gun style) repetitive taps with a light hammer ended up loosening it up.

Now I have to figure out how to remove the bushings and put in new ones.

For some reason I can't get the chap's video embedded but here is the link:

PD: many thanks to Kiwi Bloke for his help with this problem.

Best,

JHM

[Michael GilliganParticipant @michaelgilligan61133]

.

MichaelG.

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

@ Michael Gilligan: Thank you for fixing that for me.

I was able to remove the bushings, slid out very easily.

But I hould have used a wooden dowel, I tapped them very softly, did not expect to leave any marks. 8^*

The nominal dimensions according to the post by Dan Hook above are:

ID 15.0mm, OD 20.0mm, depth 12.0mm with a 25.5mm flange.

The samples I removed have these dimensions, taken with a caliper:

Bushing #: 1 2
Height: 11.9 11.9
ID: 14.8 14.9 <— has 0.1mm wear / must be the lower one
OD: 20.0 20.0
Flange: 25.0 25.0

I am now on the search for a new, modern version of these bushings ie: harder, less friction or maybe the possibility of a set of bearings which could be just 'dropped in' without much ado.

The F6802 bearings mentioned here are still available but to use them I'd have to get someone to put the quill on a lathe, not the Unimat 3.

Best,

JHM

[Kiwi BlokeParticipant @kiwibloke62605]

Posted by Julius Henry Marx on 19/12/2022 20:47:42:

…

I am resurrecting this seven year old post because I have come across a video posted ten months ago on YouTube by a chap who shows how to disassemble the Unimat 3 milling head which btw is, according to Tony Griffiths of lathes.co.uk, the same one used in the Emco Compact 5 and Compact 8.

…

Oh, I didn't know Tony Griffiths thought that. It's wrong. The Compact 5 head is completely different, being larger, with ball bearings, and the quill return spring buried inside the quill – a rather odd arrangement.

Following a PM exchange with julius, I've put *.jpg images of the Unimat 3 quill modification into my album, for all to see. I trust the moderators will remove the images if copyright is breached.

[Julius Henry MarxParticipant @juliushenrymarx92355]

Posted by Julius Henry Marx on 19/12/2022 23:28:54:

… search for a new, modern version of these bushings …

I have found what seems to be an almost drop-in replacement for the bushings in a SKF catalogue.

SKF part PSFM 142012 A51

—

Description
14MM Nominal Bore; 20MM Nominal Outside Diameter; 12MM Length Thru Bore; Bushing With Flange Profile; Oil Impregnated Sintered Bronze; SINT A51 Material; 26MM Flange Outside Diameter; 3MM Flange Thickness

—

It would seem (?) that I'd only have to remove 0.5mm from the flange and touch up/adjust the new bushing's ID to the actual dimension* of the races the bushings run on, obviously on a lathe and using a properly sized reamer.

*: my micrometer/eyesight say both races are apparently without wear at 14.98mm.

Q: is oil impregnated sintered bronze the best option available?

I am still considring the possibility of using bearings, so any ideas towards that will be appreciated.

Thanks in advance,

JHM

Edited By Julius Henry Marx on 20/12/2022 12:14:54

[Graham MeekParticipant @grahammeek88282]

I have two Unimat 3 Milling Spindles. One has been heat treated from new and the other is soft. The former is an early version and despite its age shows no sign of run-out or wear. I would only recommend using a good quality ISO 32 machine oil to lubricate the Oilite bearings. Especially for those working in an outdoor workshop.

Regards

Gray,

[david bennett 8Participant @davidbennett8]

I became so disappointed with the bearing system that I changed the whole thing to a sl/db head. No comparison.

Sorry for sideways view (again) dave8

Edited By david bennett 8 on 20/12/2022 14:54:00

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

Posted by Graham Meek on 20/12/2022 14:10:24:

> … two Unimat 3 Milling Spindles.

Could you tell me the difference between the two versions?

I guess is that the one in my milling head is the same age as the U3 it came with ie: manufactured 1980.

I have read a couple of comments on the web referring to a full length height bushing instead of two but have seen no photos or other references.

> … despite its age shows no sign of run-out or wear.

What my head has is axial play, something I found out about it while attempting to measure the spindle's runout.

Once extracted, I measured the ID on both bushings, finding a 0.1mm difference between one of them and the nominal dimension which seems to be 15mm, my spindle races measuring 14.98mm.

Do you think there is a better option to the SKF bushings made from SINT A51 I mentioned in an earlier post?

ie: one which would result in their having higher mechanical strength, less friction and longer life.

Thanks in advance.

Best,

JHM

[Graham MeekParticipant @grahammeek88282]

Hello Julius,

I cannot say what age the heat treated spindle I have is. It is something that was given to me so the origins are unknown.

It is easily distinguishable by the dark, nearly black band where the Tommy Bar hole is. The other spindle which is in my 2/3 rds full size Quorn, is from the 1980's and is distinguished by a bright band where the Tommy bar hole is. The earlier black one is probably hard or toughened and this is why there is negligible wear. I say earlier as it would make sense to machine the part straight to size and reduce the cost of the part. By not having to heat treat and grind afterwards.

The softer one will off course wear quicker. This may have been off-set somewhat by using an already heat treated raw material.

The size of your spindle is about right, and I would say based on the Shaft Based system of measurement used on the Continent that you have about 0.009 mm of wear. (Based on the 14.98 mm figure)

The Oilite bush when inserted will probably give up to 0.05 mm total clearance on your shaft. It could well be better than this if Emco made the Quill Housing bearing register deliberately undersize to crush the Oilite bushes more than usual. I have known them to play about with bush bores in the past.

Without the parts at my disposal I cannot say any further than this. I would certainly replace the bushes with SKF sourced originals. The far eastern Oilite bushes I have purchased leave a lot to be desired.

Just remember to reduce wear you need have a film of oil for the shaft to rotate on. Get the clearance too small and there is no room for the film of oil and the parts will wear prematurely.

Some of the spindles are wasted in the central bearing portion so will not benefit from a full length bearing. A full length bearing also increases the amount of power required to drive the spindle before any work takes place.

Regards

Gray,

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

Thank you for the prompt reply.

> … easily distinguishable by the dark, nearly black band …

Here's a photo of the spindle I have, seems to fit your description.

> … your spindle is about right … … about 0.009 mm of wear. (Based on the 14.98 mm figure)

I see.

I don't have much/any experience in the tolerances field.

Is this amount of wear reasonable, should it be less or should there be no wear at all? ie: is it the result of the lack of proper maintenance?

As I unmounted the spindle, I was rather surprised to see practically no oil, just some some traces of a black and rather dense (very hard to wash off my hands) grease.

> … Oilite bush when inserted will probably give up to 0.05 mm total clearance on your shaft.

The bushings I have found to replace the OEM ones are the SKF mentioned earlier and a locally made set (a company with 40+ years in the market), with what seems to be the same spec as the SKFs. I'll be getting the exact data via email later on.

> … well be better than this if Emco made the Quill Housing bearing register deliberately undersize …

The quill housing diameter, measured with the same caliper/eyesight setup used earlier, read 19.90mm and the extracted bushings read 20.0mm. Is that what you are referring to?

> … replace the bushes with SKF sourced originals.

Yes, I would not go for any other except the locally manufactured ones but I still have to confirm availability and price for the pair of SKFs. The locally manufactured ones will set me back ~ US$10.00 for the pair with the only caveat that they are 18mm long instead of 12mm, which I don't see as a problem as I can fix that on the U3 or even leave it at that if it does not cause any issues.

> … remember to reduce wear you need have a film of oil for the shaft to rotate on. Get the clearance too small
> and there is no room for the film of oil and the parts will wear prematurely.

Will do.

The quill does not have a way of being oiled, would packing grease on reassembly (like the chap in the video does) help?

In both the bushing options I have available the nominal ID is 14.0mm.

I suppose that I will have to touch that a wee bit to be able to slide in the spindle and have enough clearance for film of oil needed.

With the spindle races clocking in at 14.98mm, what ID should the bushings have before insertion?

What would be the best/more reliable method to achieve that ID sizing?

> … full length bearing also increases the amount of power required to drive the spindle …

Makes sense.

Thank you very much for your input.

Best,

JHM

Edited By Julius Henry Marx on 21/12/2022 13:10:18

[Graham MeekParticipant @grahammeek88282]

Hello Julius,

The Quill housing bore is as I suspected down on the Nominal 20.00 mm bore size. This will tend to close in the bore of the Oilite bush and give you a closer running fit. I don't think you will get a very precise reading with a vernier on this bore size. I would anticipate the actual size to be in the region of 19.95 to 19.97 mm.

The Oilite Bush I would expect to be around 20.03 mm diameter before insertion. It is best to press these bushes in or use a large washer and some studding to draw them into position.

As supplied an Oilite bush is impregnated with oil, and just for good measure they should be soaked overnight in oil before insertion. They should go for many, many hours before the need to replenish this oil.

Grease will tend to clog the bearing and stop the release of the impregnated oil in the bearing. Plus grease in a cold workshop will provide a huge source of drag on the spindle with such a small motor. As I said earlier I would oil using an ISO 32. If you oil in the recess at the top of the quill and leave it to stand, the oil will find its way into the quill. Failing that if you really want to be sure, immerse the whole quill for 24 hours in a container filled up to the flange with oil. Then allow the excess to drain out afterwards before use.

I cannot see why you are going for 14 mm bore bushes. When 20 x 26 x 15 bushes are widely available, or was this a Typo error?

Regards

Gray,

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

> … bore is as I suspected down on the Nominal 20.00 mm …   … tend to close in the bore of the Oilite > bush and give you a closer running fit.

Good thing then.

> … don't think you will get a very precise reading …

I didn't think so either but I don't have the right instrument for that yet, it is quite dear.

> … would anticipate the actual size to be in the region of 19.95 to 19.97 mm.

Right.

> … would expect to be around 20.03 mm diameter before insertion … … best to press these bushes in > or use a large washer and some studding to draw them into position.

No press immediately available. Will have to use some other reliable method.

> … bush is impregnated with oil, and just for good measure they should be soaked overnight …

Yes, I've read about that.

> Grease will tend to clog the bearing and stop the release of the impregnated oil …

Right, no grease then.

> … oil using an ISO 32. If you oil in the recess at the top …

Yes, I'll do just that.

Thanks for the heads up on the grease.

> … why you are going for 14 mm bore bushes.

No, no error.

I only found 14×20 in the SKF catalogue and the local chap offered me the same type.

I have sent them an email asking about 15×20.

Does it matter if they are longer than 12mm?

Thank you very much for your input.

Best,

JHM

Edited By Julius Henry Marx on 21/12/2022 17:19:36

[Author]

Posts