Unimat 3 Vertical Head Quill

[Graham MeekParticipant @grahammeek88282]

Hello Julius,

Be sure you get Flanged bearings, 20 x 26 x 15 is the code you want.

The length is not a problem, any additional length will not be used due the reduced portion in the middle of the shaft. The extra length might act as a small oil reservoir which is no bad thing.

Regards

Gray,

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

> Be sure you get Flanged bearings, 20 x 26 x 15 …

> The length is not a problem …

Good to know, one less thing to take care of.

A new search on the SKF on-line bushing catalogue and filtered by metric, flanged design, flange diameter 25 to 26mm, sintered bronze, 20mm OD and a 14-15 mm ID produced only four available options.

All are 14mm ID and 20mm OD, flanges 25/26mm and four different lengths: 10/12/14 and 20 mm.

PSFM numbers 142010 A51, 142012 A51, 142014 A51 and 142020 A51.

But no 15mm option to be found.

But I did find 15mm ID, 20mm OD in 15mm and 25mm lengths but both with a flange diameter of 27mm.

PSMF 152015 A51 and 152025 A51.

I guess that it will be much easier to just trim the 27mm flange to 25.5 than to muck around with the ID.

And, like you mention, a 25mm length will surely help with the oiling.

Think this one will do?

Now to see if I can get such an animal.

Thanks for your input.

Best,

JHM

Edited By Julius Henry Marx on 21/12/2022 18:19:44

[Graham MeekParticipant @grahammeek88282]

Hello Julius,

Using the above link I found this bush that will do the job, PSMF 152015 A51. You will have to turn the flange down, but that is far easier than boring Sintered Bronze I can assure you. You will need to turn this off a mandrel, don't be tempted to hold it in the chuck. The mandrel does not have to be that good a fit, and the bush can be held with a suitably sized capscrew and washer in the end.

Regards

Gray,

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello Gray:

Thanks for staying with me for this, much appreciated.

> … will do the job, PSMF 152015 A51. You will have to turn the flange down …

Yes, that or maybe the longer one for the added oil retention.

> … turn this off a mandrel, don't be tempted to hold it in the chuck.

Indeed …

> … mandrel does not have to be that good a fit …

I can make one from aluminium and put a dab of ciano to keep it in place/still. I expect that a good number of thin cuts will do the trick to get to 25.5mm.

The bad news is that SKF does not have those bushing locally (never have actually) and the other purveyor I contacted does not have 15X20.

They only have the 14×20 or 15X20.5 … <— 20.5????

In the meanwhile, I have been wondering about this:

The OEM bushings I unmounted do not look to be made from sintered bronze but from solid brass, such as SAE64 or similar (?) and most probably the original ones.

I say solid brass/SAE64 because of the shiny reddish colour ie: not the sintered brass look, which is darker and not at all shiny.

The question that popped up in my mind was this one:

If the mill were properly maintained and the spindle always oiled, a SAE64 brass bushing could (?) be a good/better option than sintered brass and maybe last longer, ie: given the type of forces at play on the business end of the mill.

Any thoughts on this?

Thanks in advance,

Best,

JHM

Edited By Julius Henry Marx on 21/12/2022 20:27:32

[Andy_GParticipant @andy_g]

Posted by Julius Henry Marx on 21/12/2022 20:25:42:

I can make one from aluminium and put a dab of ciano to keep it in place/still. I expect that a good number of thin cuts will do the trick to get to 25.5mm.

The bushes will be oil impregnated, so I doubt that glue would stick to them.

The bushes in that picture look like sintered ones to me.

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

> … bushes will be oil impregnated, so I doubt that glue would stick …

Quite so.

Just what was I thinking? 8^° Thanks for that.

And if it did stick it would muck up the pores jst as poor machining would.

 

> … bushes in that picture look like sintered ones to me.

I only have web photos to compare to what I am actually seeing in front of me.

eg:

The ideal thing would be to get my hands on a manual/parts list for this mill head/spindle.

It has proven absolutely imposible to find, not even a part number for the milling head.

But it seems that you are on the dot with your identification.

I took the highest magnification photo I could with my oldish digital camera, then cut and enlarged a portion of the image.

Rather blurry as at that magnification you need absolute immobility, but the detail seems enough for a veredict:

So thanks for that also.

But the question still stands: would a properly maintained and maybe easier to source/make SAEnn brass bushing be an improvement?

Thanks a lot for your input.

Best,

JHM

Edited By Julius Henry Marx on 22/12/2022 10:55:54

[Graham MeekParticipant @grahammeek88282]

Hello Julius,

I regret to say I have to agree with Andy_G. Those bushes are Sintered BRONZE, Brass is softer than Bronze so making the bushes out of brass would be a retrograde step. Plus they would need to be constantly oiled to give anything of a service life.

You also run the risk of permanent damage to the spindle bearing surface. I don't consider this to be an option. You should always replace like with like.

I have just done a Google search for the above bearing and had several results. As you are having difficulty getting SKF you will need to settle for some other make. You have already considered a compromise with substituting the bushes with brass. I have seen these bushes listed at £1.86 on a well known auction site.

Also the glue would not be something I would be willing to try.

Regards

Gray,

[Graham MeekParticipant @grahammeek88282]

PS Your reply above came in while I was typing,

The Quill was always supplied as an assembly, if my memory serves me correctly.

Regards

Gray,

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

> … have to agree with Andy_G.

> … Brass is softer than Bronze …

> … run the risk of permanent damage …

My lack of experience with all this evidently put me in a spot.

> … difficulty getting SKF you will need to settle …

Or try to get them from abroad.

> … considered a compromise …

Not anymore, you are the one who knows, so sintered brass it will be.

> … Quill was always supplied as an assembly …

I expect that a manual for the milling machine or milling head would have had (?) an exploded diagramme such as the manual for the U3 which has a complete diagramme and parts list for practically everything.

I will continue to try to come up with something locally and if not, put this on a back burner till I can get the bushings from abroad.

Thank you very much for your input, you have all been very helpful. 8^D

Best regards,

JHM

Edited By Julius Henry Marx on 22/12/2022 11:11:31

[bernard towersParticipant @bernardtowers37738]

When you say sintered brass I presume you mean bronze, and using sintered material extends the maintainence period. You could also buy a sintered blank and machine your own.

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

> When you say sintered brass I presume you mean bronze …

Yes, I did. I realised my mistake after my last post but the editing period had lapsed.

> … using sintered material extends the maintainence period.

Yes.

But for whatever reason I have the idea (probably wrong) that sintered brass has, due to its manufacturing process ie: pulvimetallurgy, a lower mechanical resistance in relation to properly specced solid bronze.

> … could also buy a sintered blank …

Yes, I guess I could.

But my lathe skills are not up to par for such a task and then I don't count with all the needed tools to achieve a decently made piece. eg: a way to make a perfect bore (need a reamer) and then accurately measure the result (bore gauge).

Perfect concentricity would be paramount importance here and I have read that below par machining will produce blocked pores through which oil will not flow, making the sintered option a plain bronze bushing.

So at the moment I am rather limited in my choices.

Thank you very much for your input.

Best,

JHM

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

Happy New Year to all!

> I will continue to try to come up with something locally …

I finally managed to get a hold of a pair of sintered brass bushings, but not 15×20 as required, dimensions that (for whatever reason) is not available anywhere locally.

Purchasing them from the manufacturer made the 2 hour trip worth it: they cost me less than half the amount the shop downtown wanted for the exact same thing.

The bushings are (ie: were) 15.00mm x 22.00mm x 23mm with a 25.00mm x 3.20mm flange.

I mounted them on the spindle which in turn was mounted between centers on the U3 and slowly took down the 22.00 OD to just 0.02/0.03 over the nominal 20.00 needed, at least that is what my micrometer/eyesight combo says.

I did not want to risk going for the exact 20.00mm (can't fix that) and reasoned that if after they were in place things ended up being too tight, I could always spend a few $ to have someone with a properly sized reamer hone them a bit.

Popped them in the freezer compartment while I very slowly heated the quill just enough so that I'd need a cotton glove to handle it and everything went as expected.

Exactly as the chap who runs the bushing manufacturing operation said, turning the bushings resulted in most if not all the oil they were impregnated with being expelled, so a 24hr. soaking in SAE10 or 20 is next.

As the quill now has a short (~20mm) void between the bottom ends of the new bushings, he also suggested I go 'old style' and put in a piece of felt (or similar) soaked in oil to fill that space.

I have some fiberglass insulation weave of the right width/thickness which may do well enough.

That, he said, would make the new bushings 'eternal'. 8^°

So far so good …

I'll post the result of all this when the milling head is assembled and I can check the runout.

Best regards,

JHM

Edited By Julius Henry Marx on 02/01/2023 12:22:02

[Julius Henry MarxParticipant @juliushenrymarx92355]

Hello:

Posted by Julius Henry Marx on 02/01/2023 12:19:02:

I'll post the result of all this when the milling head is assembled and I can check the runout.

I've finally had time to assemble everything and check the runout on the spindle after replacing the OEM bushings.

I think things turned out quite well.

The runout turned out to be very close to nought, with the clock's needle barely moving to one side of the marking.

Maybe about 1/3 of 0.01mm?

I'll leave it to you all to have a look and opine on the matter.

Best,

JHM

 

 

 

Edited By Julius Henry Marx on 08/03/2023 15:22:20

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