T and C Workhead - Bearing Seal Stiction

The Timken bearings Hercus originally fitted in their No.1 grinder workhead have at some more recent time, had their seal configuration revised. They seal even better now if stiction is anything to go by, great on a boat trailer, not so great in a workhead. I have searched Australian, English and American eBay for the older bearings but to no avail.

I showed the workhead to Alan"C-47" and Alan agreed that the seals would prevent the free turning of the spindle required for flute sharpening. Alan's Astra T and C workhead spindle spun without resistance. Alan suggested the possibility of using a bearing seal such as is found on a conventional sealed ball bearing, of a size that would fit the protruding cone. The cone is 46.4mm in diameter and protrudes 2.75mm. A search for something existing that would suit has proven fruitless.

I spoke with the bloke I work for, a serious petrol head, who suggested a DIY alternative along the lines of a disc that would close off open side of the bearing and utilise an O ring seal between the inner opening of the disc and the protruding cone. The O ring would be located in a groove in the disc edge and could be adhesive fixed in position. The fit of the O ring could be adjusted to provide minimal turning resistance by adjusting the ID of the disc. The OD could be a friction fit in the workhead casting.

I bought a metre of 1.6mm diameter O ring cord and a bottle of Loctite 406 as a start. ( I have found an eBay seller in the Czech Republic offering 1mm diameter cord. )

Hercus intended the bearings to run in oil. Rather than weeping oil attracting grinding dust, I'm thinking grease might stand a better chance of staying in place.

Any better ideas?

Here are the original Timken LM67048L cones on the spindle -

Attachment 318833



The new Timken LM67048L-A cone -

Attachment 318837



And the non sealed version from Poland -

Attachment 318835Attachment 318836

BT

An o-ring as described might work, but...
O-rings are really meant as static seals. While some are pressed into service with relative motion between the parts it's not going to give the best seal possible as there is no light pressure to cope with minor deviations of the mating surface.
I fixed the vertical head in the mill with a thing that SKF call a V seal or a V ring
All-rubber V-rings
They are not horribly expensive and consist of a rubber collar that fits on a shaft with a thin lip lightly pressing against the other part of the housing.
Attachment 318845

Might be worth considering if you are chasing low friction. (This is a mod that I've done so you may need to alter the T&C cutter housing to suit)

Michael

I'm a fan of v-rings also, if they can be adapted in. I rework some spindles to include them, by removing the labyrinth, and putting in a ceramic land for them to run on.

Really smart seal, they are best when static. But open up when spinning.

Regards Phil.

Failing the above, how about an air spindle? well an air spindle with a difference lol
I came up with this idea for my lathe and all the worries that are around re turning cast and the headstock bearings.
Lose the seals, add an air line and pressurize the casting at 0.1psi. Of course its something else to get in the way and to remember.


Stuart

A V ring? Why do I automatically think of G string?

Anyway that sounds the go.

Stuart. I like the sound of providing a slightly +ve pressure in the headstock. How do you regulate it to 0.1 psi? Do you run it all the time or only with ci?

Simon


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Quote:

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Originally Posted by simonl

Stuart. I like the sound of providing a slightly +ve pressure in the headstock. How do you regulate it to 0.1 psi? Do you run it all the time or only with ci?

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Like many of my ideas it came to late for the job I was doing....So its waiting for "next time"...as to regulating 0.1 psi, I'm thinking regulate and low as you can get + a small hole should do it? then I'd get a chance to use my 0.001psi gauge lol

Stuart