Lubricate (Webster’s Dictionary definition): To make smooth or slippery, to diminish friction by applying a lubricant.

(To ensure that tow surfaces in relative motion do not come into contact)

Lubricant (Webster’s Dictionary definition): A substance, e.g., grease, oil, soap, etc., that when introduced between solid surfaces which move over one another, reduces resistance to movement, heat production and wear by forming a fluid film between the surfaces.

In order to lubricate successfully, a basic understanding of a lubricant’s function is necessary. A lubricant, whether it is oil or grease, can at any time perform up to six basic functions simultaneously. These functions are to:

1. Reduce friction
2. Reduce wear
3. Absorb shock
4. Reduce temperature
5. Minimize corrosion

Reducing friction is the primary friction of a lubricant. It does this by separating the two contact surfaces and allowing them to move over one another via the lubricant’s viscous shear planes.

With the introduction of a lubricant, we no longer have the asperities of the moving surface in collision: by virtue of this fact, the wear element particulates are significantly reduced and component life is extended.

Shock absorption is particularly significant within gear meshes. When meshing gears are not lubricated, the mating teeth set up shock wave. This is heard as a “chattering” sound. This type of shock often results in gear teeth fracture. Introduction of a lubricant reduces the chattering, acting as a “shock absorber”. When a gearbox is properly lubricated, it turn more smoothly and relatively noise free.

A major benefit of reduced friction is reduction in operating temperature. Caution must be observed in the overall assessment here. Because excessive lubricant may cause fluid friction which may in turn raise the temperature.

Assuming that the correct quantities of lubricant are used, lubricants can be an excellent dissipater of heat, especially in recirculative oil (or splash oil) systems where the oil is passed over the moving part – where it not only lubricates, but absorbs the heat and returns to the reservoir where it cools before recommencing the cycle. (Sometimes it is necessary to pump the lubricant through an oil cooler, which will allow for a smaller reservoir.)

MINIMIZE CORROSION

If a lubrication barrier were not in place. Moisture in the air would eventually cause oxidation. Leading to corrosion. Lubricants cling to the element surface, providing a barrier against moisture. Again, the choice of lubricant type is critical because some lubricants act as a catalyst, trapping moisture droplets and holding them at the element surface, increasing the oxidation and corrosion process.

SEAL OUT CONTAMINANTS

Basically stated, lubrication keeps the dirt contaminants out. Dirt is evident in all aspects of surface contact. It may show up as metallic wear particles or silicon particulates. The lubricants job is to “flush” these contaminants out of the bearing surfaces so that they may be wiped away, as in the case of the grease, or caught in a filtration medium (oil). Generally, the lubricant will also act as a seal against outside dirt ingestion.