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Unimat 3 Vertical Head Quill

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Kiwi Bloke04/02/2015 10:21:35
223 forum posts
1 photos

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?

John Olsen06/02/2015 05:02:12
984 forum posts
86 photos
1 articles

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 Bloke07/02/2015 00:30:37
223 forum posts
1 photos

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 Olsen07/02/2015 04:57:51
984 forum posts
86 photos
1 articles

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 Bloke08/05/2015 08:03:21
223 forum posts
1 photos

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 Gilligan08/05/2015 08:33:56
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13780 forum posts
599 photos
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 Hook22/10/2015 01:10:06
3 forum posts

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 Bloke01/11/2015 10:13:03
223 forum posts
1 photos

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 Hook01/11/2015 23:27:08
3 forum posts

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 Gilligan02/11/2015 15:06:54
avatar
13780 forum posts
599 photos

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 webster02/11/2015 16:43:03
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2197 forum posts
32 photos

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

Kiwi Bloke03/11/2015 09:50:08
223 forum posts
1 photos

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.

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