Thread: Lip Seals and Heat Generation

I probably should have posted this before the thermometer thread.....

Yesterday I wanted to establish once and for all whether the seals in my mill's vertical head were responsible for the heat that plagues the head when it is run for a short time. The non back geared speeds range from 500 - 1140 rpm. When I used the mill and it was often before I acquired my second mill, I would only use the lowest speed and it became hot after a few minutes of continuous running. So the second mill, the 13, which has 2 horsepower and power feed and doesn't run hot became the mill of choice for vertical work. The little Hercus however can turn a 6 inch saw on its labyrinth sealed horizontal arbor and could turn it ad infinitum. The 13 can only manage 5 1/2".

Michael suggested that bearing preload might be a contributor to the heat problem so I thought I would remove the upper end cap housing the seal and the spacer the seal seals against and mount them on the lathe. I removed the garter spring before commencing a few tests. With the spring in place I'm sure the head would have been generated faster.

Running the lathe at 900 rpm for 30 seconds produced heat in the spacer that was bearable to touch, an additional 60 seconds rendered it nearly untouchable. I could hold the spacer for about 6 seconds .

The original seals were Flaseal 13297s. The replacement seals I have are made by NAK. Seal size is 2.5" x 1.875" x 3/8". The sealing lip is, as close as I can measure, 1.848", the outer diameter of the spacer on which it seals is 1.873". When the spacer is installed in the seal there is considerable turning friction. I downloaded a Timken seal catalogue last night, all 709 pages worth, but it does not identify the internal lip dimension on their similarly sized 472041 and 482041 seals. I'm wondering if there is variation among manufacturers??

The Timken seals are cheap enough in the States but shipping isn't.

When I mentioned this problem earlier Phil "Machtool" very kindly posted to me a V Seal made by NAK for appraisal. It looked promising so I purchased a pair of similar seals from SKF. These seals would mount on the spacer and in the case of the bottom seal, the spindle. The thin lip would need to seal against a sleeve because the seal's OD is less than 2 1/2". What I would do is bore a dummy sleeve to gauge the fit of the seal and test run it in the lathe to see if I have a cure.

An easier cure though would be to try another lip seal. Ben and a few others say their vertical heads are cool running. (Bruce isn't one of the few because he has no seals in his!) It would be great to hear what seals are fitted in those that have them.

Bob.