Is lubrication necessary for polymer bushings?

Like all things it depends on the type of plastic used. The thing is that many lubricants can damage the plastic causing premature failure. Also they can cause dirt to get in and act as an abrasive. I would say if the manufacturer does not indicate that a lubricant should be used don't bother.

All those I know of are selected for the self lubricting properties. Oiling or greasing them would attract dirt and embed in the breaing and wear the shaft.

In some cases the old wooden bearings were better left dry when running in sandy soils as the bearing were cheaper to replace than the steel safts that the sand and grease cut in two.

The bearing mateiral, load and working condions all need to be taken in to account when selecting a lubricant.

Gordon

Hi There all

I am under the impression that any where that there is friction there should be lubricant. In this case I would use water to cool and keep the bearing clean.

Not a practical suggestion. Water + steel = rust.

John

Water, lignum vitae & monel on hydroelectric turbines.

gc

what?????????????????????????????????

the man is trying to solve a problem. your no help!!!!!

Hi Gamza,

Thanks for the support. You saved me the trouble of telling Gordon there's no comparison between the type of equipment I'm asking about and hydroelectric turbines. Don't understand why he even brought it up. I suppose he was trying to make some point about the wooden block bearings but even that is a far cry from the modern polymer bushings that I was asking about.

Did you catch Richard's post (#10)? He mentioned wooden bearings used in old paper folding machines, so I guess maybe Gordon was relating to this. Still has nothing to do with the question. Richard gave some good info.

In regard to the posts that suggest RTFM, most user manuals do not even mention this topic (polymer bushing lubrication). Guess I could pick a random manufacturer and ask the question but then that's why we have this forum...

Thanks,

John

Using plastic bearings are better polymer bushings for you mentioned.

i would recommend treating the shaft with a slick 50 grease. you would have to remove the Bering from the shaft then heat the shaft to 85-100 degrees (not very hot and could be achieved by putting it in the sun till hot) then apply the grease to a soft rag and rub it in for about 15-20 min.. This will allow the p.t.f.e. to impregnate the metal shaft, thus coating the shaft with the polymer. this is how slick 50 treats car engines.

all it takes is heat and friction to allow the shaft to accept the the coating. polymer against polymer is like rubbing ice against ice, it's very slippery.

i worked very close with the developer of this product. jonco industries.

petrolon is just the marketing company that private labeled this product called slick 50.

Hello Gamza,

"Slick 50" never occurred to me for this application. Good suggestion. I'll give it a try.

Thanks,

John

What does the packaging say? If it does not mention any type of lubricant to be used, or if the bushing has a greasy feel to it (e.g. like with a nylon bushing), then lubrication is unnecessary. On the other hand, if a particular lubricant is specified, then use only it.

Graphite powder might be an option, being inert and non-sticky. I have freed up small, sticky mechanisms with plastic bushings (rotating or sliding) by rubbing the metal shafts with a pencil. As mentioned, some plastics are lubricitous by nature, and others enhance this with additives, such as moly (molybdenum) impregnated nylon. With the right plastic, no lubrication is necessary.

RTFM

RTFM?

Read The _______ Manual

GC

the manual has nothing to do with this, why all the dumb comments. it's one thing to be dumb, but when you open your mouth you let us know.

The general question about lubricating a polymer bearing is too broad to provide a satisfactory answer except to say that if the right material is used the answer would be no.

The right polymer (and associated fillers) do not require any lubrication. Proper polymer bearings are Class III plane bearings and are designed to run without external lubrication. Class I and II (babbit, bronze, and Oilite are three types) must have a separate lubrication independent of the source.

Carl

We manufacture a number of products using oilite, bronze, nylon and acetal bearings. Here's some information from our experience.

1. A bushing type bearing, by it's nature generally should have a lower coefficient of friction than the shaft material.

2. Using a shaft and a bearing of the same material typically results in galling and rapid failure. The bearing should be less noble than the shaft.

3. Oilite bushings are fine as long as the impregnated oil lasts. Appropriate for both linear and rotational applications that generate little heat, which tends to exhaust the oil more quickly. Load and RPM's are the factors to consider.

4. White lithium grease is an excellent lubricant for polymer bearings.

5. Nylon is not a great bearing material. Newer technology materials like acetals have a lower coefficient of friction and last longer. Nylon against aluminum and steel to a lesser degree will actually lock up with moderate pressure.

6. Bronze (932) bushings will carry a heavier load at higher temperatures than oilite which are sintered and have less surface area.

7. Having replaced thousands of wood bushings on old paper folding machines, they absolutely must be oiled. Without oil, they'd last about 5 minutes. Other than normal wear, the most common cause of failure is a blocked oil hole.

8. Temperature can be a significant problem with any polymer bushing. Different plastics have different rates of expansion with increase temperature. But a good rule of thumb is .0001" change per inch per degree F. That means a 1" thick piece going from 30 to 90 degrees F will increase in size by .006". That can cause crimping on a shaft if sufficient clearance isn't allowed. This increase pressure will force out the lithium grease, and increase the bearing temperature which will cause softening and deformation.

Hi Richard,

That's a lot of good information. I really appreciate it.

I have actually tried white lithium grease but was not able to benchmark it against a bushing with no external lubrication to see which performed best (less wear).

Take the case, say, of a generic lawnmower with plastic wheels. One poster suggested using water as a lubricant! Typically, a mower will sit unused for extended periods of time between uses so that suggestion would only cause the shaft to rust.

One post suggested that any external lubricant will only attract dirt and debris. That's a good point.

I like the one about using Slick 50 (PTFE). What's your feeling about this?

Most manufacturers don't provide info regarding the use of lubricants on plastic bushings used in homeowner products. I suppose this could imply that no lubrication is necessary.

Thanks,

John

Water....very bad idea.

Attraction of dust etc... yes but, not as bad as no lubrication.

Slick 50...don't know anything about it except that it's reported to work well in engines, which don't have plastic bushings in them to my knowledge. Still might work, I'm ignorant on its technical features.

Home product manufacturers...the typical life of a home yard appliance is expected to be short. Most yard tools are used for short periods of time and only sporatically. At that, they don't last long. If a consumer grade tool were used professionally for multiple hours every day, a few weeks would probably be its life cycle. Commercial grade tools do the same thing, but use more durable parts, generally have a maintenance schedule that includes lubrication and cost more...for a reason.

The short answer is yes and no. Just any old polymer will not get satisfactory performance like the range of polymers that have mechanical, physical, and thermal properties that are optimized and suitable for greaseless bearings. Like in most things engineering and design is just a big game of trade-offs as it is very difficult to have it all.

A plane bearing that performs without lubrication is a Class III bearing and a plane bearing that requires lubrication from outside the bearing is a Class I, and a bearing that requires lubrication but has it available from within the wall (example is a sintered bronze like Oilite) is a Class II plane bearing.

The applications that you gave are all very low in performance requirements so you could get away with a great many products that are not lubricated. On another note, silicone is not a lasting lubricant for any application because of its physical characteristics.

Thanks for the info CK.

-John

Lubrication?

Yes ,Anytime-any journal/bush combination-prefer cetralized oil flow-closed circuit.

If not possible-have at least grease! Lithium-Sodium-Potassium.Silicone is not GREAT.

Your Insurance -can do you no harm.

Lubrication has to take in all factors.

I had a John Deer Rotary Hoe that used wooden boxings for bearing. For you young guys that's two blocks of hard wood with place cut for the shaft often used in horse drawn machinery. We kept a lot of it around as it still did the job just fine.

The bearing ran 5 inches from tines that kicked up dirt. In clay soils greasing the bearing every 4 hours worked fine. But in sandy soils the sand combined with the grease and circulated in the bearing so fast you couldn't grease it often enough to keep it from cutting the shaft in too. To replace all the wooden bearing cost $15 and had to be done ever year or two with no grease and were a 1 hour job. With no grease the shafts cost $100 and had to be replaced ever 3 or 4 years along with the bushing and took all day to replace. What would you do if you had sandy land.

GC

it's nice to remember the old days but what does that have to do with this.

no wood wheels and berrings here!

There are still wood bearings being used. There are still Babbet bearings being used.

You can't blindly pick a lubricant unless you know the:

Shaft & bearing

material
size
loading
area of contact

The speed, duration, if the load is rotary of fretting and more.

The environment the bearing runs in. [the pont with wood boxings in sandy soil & hydroelectric power]

All materials have documentation on how to use them RTFM works every time



They almost all apply to a lawn more with plastic bearings.

Do you have a lawn service, 2 acres or a 10 x 20 foot lot? Are the wheel bolted on with stainless steel, black iron or Cad plated bolts. Do you live on clay soil on on a sandy beach.

Try thinking just a little.

Gordon

Hi Gordon,

Lighten up dude! Picture a man trapped in a time-warp...

He's sitting on his four year old generic riding lawn mower. He notices that the 1/2" steering shaft that goes from the steering wheel down to the tie rods has a lot of slop in it. He removes the shaft and discovers that it ran in two polymer bushings, one at the top and one at the bottom. Both bushings are worn out (paper thin). The steel steering shaft, however doesn't appear to have suffered a lot of wear.

So he goes to the local time-warp lawnmower store and purchases the two bushings that he needs. When he asks the technician about lubricants, the tech says "I've heard some people say that silicone grease is good but then I've heard others say that no lubricant should be used. Personally, I don't use any lubricant when I replace plastic bushings".

So he returns to his well-watered fescue field still unsure what to do about lubrication. He installs the two bushings in their respective brackets (one at top and one at bottom).

Before he inserts the steering shaft, should he A. use no lubricant, B. use water (as has been suggested), C. use a white lithium grease, or D. it's a problem that can't be solved, he'll have to use a hydroelectric turbine to finish cutting his grass!

Cheers,

John

John,

You are a poet

Great!

Let people think

mm

hi john,

I suggested the p.t.f.e. treatment above, using a slick 50 grease as a vehicle to impregnate the metal shafts. (see my thread above) we were told that it was a polymer Bering, thus impregnating the shaft with a polymer film should take care of this problem.

I'd like to speak to your question, what is the speed of dark? lol

nice mind bender.

one way to measure this that came to mind off the bat was,

apply a beam of light, and that will cause the dark to part at the speed of light.

Hi Gamza,

apply a beam of light, and that will cause the dark to part at the speed of light.

True, but another poster, (different forum) suggested that dark had to be faster than light because it always stayed just ahead of the approaching light.

John

hi john,

i see your point, and it is intriguing. Another way of looking at it is that the light is ripping the darkness out of it's way. which would make the darkness slower then light. also not to get biblical on you but God said that light pierces darkness.

i love the thought that this question produces. would love to here more.

gamza

what is the absence of chaos?

Hi Gamza,

In my humble opinion, dark must be at some sort of a rest state. It absolutely is the luminiferous aether upon which light propagates. Think about it, Without dark, light would have no meaning because there would be no darkness to overcome! On the other hand though, without light, we still would have darkness. We just wouldn't be able to see it since the rods & cones in our eyes would have nothing to work with.

I tend to ramble a lot don't I?

what is the absence of chaos?

Order comes from disorder comes from order comes from disorder comes from order...

Cheers,

John

e=mc2

i tend to keep it short unless I'm trying to teach someone something. good points. but i tend to be drawn by the light, for without it we would be like blind squirrels, looking to pick up a nut now and then.

gamza