Thread: Hercus mill bearing lubrication.

Here's a few questions regarding the idea I have for lubricating the bearings in a Hercus Mill via a gear pump.

Which of these pumps would do the job?

http://www.omega.com/ppt/pptsc.asp?r...200&Nav=grel01

Things to consider -

I would prefer a relief valve.

Smallest pump and outlets that will do the job.

Pump only as I would prefer to source my own motor.

What motor would I need to run the chosen pump?

Would SAE 75W-90, GL 4 or GL 5 oil do the job?

What is the SSU of the above oil? This will have a bearing on what pump I need.

I think that will do for now. I will probably have more questions.

Nev

Firstly, what is the current factory fitted method of oiling the spindle bearings??? Are they roller/ball bearings or plain bearings

Are they lubricated by being grease packed or fed by an automatic oiler???

Why not an oil pump off a car engine??

Oil would be around an ISO68 grade. 75-90 would be way too heavy

The Hercus has Tapered Rollers with small oil cups at the side which feed to the bottom of bearings.

I don't want an oil pump from a car. Too much stuffing around to find one which will fit and work.

Nev

I guess I have to ask, what is wrong with the oil cups???

It seems that an ISO68 oil is the same viscosity as an 80W oil and has a Saybolt Viscosity of around 350 at 100 deg F. Am I correct?

Nev

Nev,

Sounds right to me. SAE 80 W gear oil has the same viscosity as SAE 25 W engine oil according to this comparison chart - http://www.bobistheoilguy.com/visc.html.

I use Mobil DTE Heavy Medium ISO 68 circulating oil to lubricate the roller bearings in both my mill and in my Model AR lathe. The decision to use this oil was based on advice provided by Hercus and Mobil Technical Assistance.

The Hercus mill operator's instruction book recommends the use of Mobil Vactra Heavy which is no longer vavailable. The DTE was the recommended replacement.
I use Mobil Vactra 2 way oil on all the sliding components on my lathes and the mill.

Why do you want to pump oil into the mill spindle bearings? With the original oil cup setup the oil leaks out at the bottom of the bearing caps. Pumped in it will out under pressure. My mill has worked well enough for, I guess, close to forty years with oil cups.

One final comment, make sure there is no grease in the oil nipples, in particular the cone pulley.

Best regards
Bob.

Originally Posted by Anorak Bob

Why do you want to pump oil into the mill spindle bearings? With the original oil cup setup the oil leaks out at the bottom of the bearing caps. Pumped in it will out under pressure

I've got that all covered, I hope. It will all be sealed. I've already sourced all the seals I need and with a few modifications to the mill housing and spindle and associated parts I can pump oil through to the bearings through a new hole above where the oil cup holes are now and use the originals as the drain back to a sump, then through a filter and back to the pump to do it all again.

I have not had time to do much besides dismantle the mill and do a lot of measuring and thinking at this stage, but when I start to reassemble (after cleaning, painting etc.) I will take pics and try to post the rebuild process and modifications. I know it's a lot of work and some may think I'm crazy, but I like a challenge. I still havn't finished the Advance Lathe rebuild I started years ago.

The gear pump is proving a challenge as the link above talks about Saybolt Viscosity when refering to the pump specs and this confused me at first, but after some research I think I'm starting to understand some of it.

Nev

Originally Posted by Anorak Bob

One final comment, make sure there is no grease in the oil nipples, in particular the cone pulley.

I know what you mean. Fortunately, I never ran mine so it's ok. If I had of, I would have been in trouble because the lubricant betwen the pulley and spindle had turned to a very stiff, glue like substance that would have been useless and I suspect would have damaged the spindle very quickly. If the mill has been used regularly it may not be a problem, but if like mine, which I suspect has sat idle for many years, then disassembly is the only cure.

Nev