Grease instead of oil

[ozzie46]

   Since I have my lathe torn down to fix the headstock bearings would it be better to install grease nipples to replace the ball type oilers on the top of the headstock?
 
  The bearings are taper bearings like the front wheel bearings in a car.  The manual says to oil the bearings daily but I think it would get better lubrication with grease than oil. There is no reservoir for the oil and it can run out freely so the bearings only have what ever thin film of oil clings to it.

 
  Any thoughts?


  Ron

[bogstandard]

Ron,

It is a misconception that bearings should always be greased.

Too much grease in a bearing can actually cause it to fail. If grease fills the bearing say more than 50% full, there is a great risk of moving parts hydraulicing the grease, and causing the bearing to shatter under the excess pressure.

Excess oil has the opportunity to drain away, but still leave a film of lubrication in the bearing. So IMHO, do as the manufacturers recommend, but do follow the daily (or before running the machine on the first start of the day) routine religiously.


Bogs

[ozzie46]

  Thanks John, Will do.

  Ron

[Bernd]

Too much grease in a bearing can actually cause it to fail. If grease fills the bearing say more than 50% full, there is a great risk of moving parts hydraulicing the grease, and causing the bearing to shatter under the excess pressure.


Bogs

John,

I gave that statement a bit of thought. It does make sense until you think that the bearings of a car wheel are packed in grease. Also boat trailers have grease fittings to grease the wheels so water can not get in. This then would make you statement untrue.

I can see if the grease had no place to go and you forced it in and it was under pressure. But in a bearing such as a car bearing the grease can get out eventually.

Bernd

[Bluechip]

Bernd

Over-lubing things can cause them to seize up. When I was at IBM, it was possible to lock these things up solid & smoking hot by over-oiling them.

http://www-03.ibm.com/ibm/history/exhibits/attic3/attic3_024.html

( Even found a pic.     )

Dave BC

[bogstandard]

Bernd,

Go down the page a little bit on here and it will tell you how much grease should be used in a bearing for different applications. You would class a lathe bearing as medium speed.

I couldn't find any at the moment referring to the reason you only partly fill a bearing with grease, I will have to go thru my favourites as I am sure I have all the information there. But what I stated about hydraulicing in an overfilled bearing is correct.

http://www.ntnamerica.com/faq.htm

These others tend to stipulate oil feed for a taper bearing, exactly as I was saying.

http://machinedesign.com/article/tapered-bearings-1115

http://www.freepatentsonline.com/4400040.html

http://www.renewablelubricants.com/RenewableLubricantsManual_BioBearingOils.html

I can only go by information supplied to me over many years by service manuals and manufacturers service lists relating to bearing maintenance, which I would prefer to follow, rather than hearsay and wives tales bandied about on the net.


Bogs

[boatmadman]

I have to agree on the too much grease is bad statement.

I have seen bearings overheat and fail due to excessive grease churning inside the bearings on big pumps where the young mechy thought he was doing right by pumping the stuff in till it oozed out of the ends!

As for car wheel and boat trailer comments, those bearings are usually packed with your fingers on installation or cleaning, so no real pressure will build up.

Ian

[Bernd]

As for car wheel and boat trailer comments, those bearings are usually packed with your fingers on installation or cleaning, so no real pressure will build up.

Ian

One one of my boat trailers there is a grease fitting in the center. The trailer manual tells you to pump in grease until you see the old grease come out the back. The trailer carries a 3000lb pontoon boat at 65mph. I've had it for five years now and have had no heating of the bearings yet. There also boat trailers that have what are called "bearing buddys". They have a spring in them to keep a constant pressure on the grease so no water can get into the bearing while you launch or pull the boat out of the water.

I'm not saying that the information is wrong here. It's just that certain applications use different methods. I can understand using oil in high speed spindles. And I'm sure nodbody can pack a wheel bearing 100% with grease.

Bernd

[ozzie46]

 This is all nice to know.  Thanks guys

  Ron

[tinkerer]

Sealed bearings are pre-packed to spec. Axle bearings are not loaded (torqued) in most cases and are considered low speed bearings. Aircraft wheel bearings are torqued, but require regular maintenance. Spindle bearings can be more like bushings and are replaceable. High speed bearings are usually not packed with grease (unless designed to fail) and ride in an oil rich environment. If you service it with a grease gun, I doubt it can be over serviced.

[Baldrocker]

Hi guys
I realise MadModder is all about modding but surely in this
context "follow manufacturers instructions" is the creed to follow.
BR

[ozzie46]

  I didn't realize that lubrication could get so involved. And to think I was a mechanic 30 years ago. Oh well.

  Having taken in the info presented I think I'll stay with the oil.

  Thanks for everyones input.


   Ron

[bogstandard]

Ron,

Getting back to your original question, I suppose you could fit drip feed oilers like these.

http://rdgtools.co.uk/acatalog/Drip_Feed_Oilers.html

Just set the drip rate, say one drop per 1/4 hour, then on starting to machine, flip them on, flip 'em off when you have finished.


Bogs

[chuck foster]

wow .............i never thought over lubing could cause a bearing to fail.

you learn something new every day, thanks guys.

chuck