How does grease do its job ?

[Mrwurm]

Well, its pretty obvious that grease slows down wear and makes things work smoothly. This is easy to understand on my trailer as the hubs use a pressurized system to keep grease in contact with the bearing surfaces. What I don't understand is how grease can do its job in other applications when it is displaced by the motion of the bearings. I'm assuming that grease is too thick to flow and, once a bearing revolves once or twice, it pushes all but a thin film of grease out of the area. So, if I'm correct, why do we put so much grease on things when its just wiped away by the bearing and is too thick to flow back where it needs to be ?

Help me understand this ?

 

[3RRL]

When moving components heat up from friction and work loads, grease becomes more viscuois and works just like oils. When it cools, it "hangs" around the component. Some is lost after a days work when this happens and that's why you have to re-grease your tractor's pins and bushings. During the heating up, a sort of capilary action takes place that draws from the main body of the grease deposit to lubricate the moving components and provides a thin, protective film.

Generally, grease is used in slow moving, sliding or rotating applications where it would be hard to put a reservoir or submerge it in another lubricant such as oil. Oils, in their different viscosities are generally used to lubricate higher speed applications and where it's possible/practical to have a lubricant reservoir available. An example is light spindle oils used to lubricate machinery or air tools at very high rpms. A heavy viscosity oil for your tractor's transmission or rear ends. Bearings fall into both catagories, some being hi-speed and others low speed. Some bearings have shields that not only keep dirt out, but also grease in.

 

[Soundguy]

Also.. keep in mind that not all greases are the same. For instance.. you can get flowable grease.. look at JD cornhead grease.. 0#.. etc. It will settle in a sump after use.. that JD grease is a favorite for people rebuilding old steering gear boxes with worn seals.. etc.

There are also pourable greases.. that fall somewhere between thick oils, and thin greases.

I've seen adds for 300w oil for marine gearboxes, and other heavy oils for model a gearboxes.. etc..

Soundguy

 

[jimg]

That intersting...so the less viscous grease is applied w/ a std grease gun?

 

[Soundguy]

</font><font color="blue" class="small">( That intersting...so the less viscous grease is applied w/ a std grease gun? )</font>

Yep.. JD cornhead comes in sealed tubes.

I've seen pourable grease and marine lower end lube come in flip top 'squeeze tubes', as well as in wide mouth plastic bottles.

Soundguy