Most kinds of machinery with moving parts need grease for lubrication. Machinery needing grease require a special tool to get the grease exactly where it’s supposed to go. Thus, the grease gun.
What is grease?
Grease consists of oil combined with a substance which makes it thicker, such as lithium. Grease is used in places where it is impractical to lubricate often, or where plain oil—being runny—would quickly leak away.
How does a grease gun work?
A grease gun consists of four main parts: 1) a grease tube or cartridge which holds the grease, 2) a plunger and spring which keeps pressure on the grease within the grease tube (similar to how a syringe works), 3) a lever, trigger, or pump which provides pressure to force the grease out of the tube, and 4) a flexible hose or stiff tube through which the lubricant is forced from the grease gun and into a grease fitting on the machine being lubricated.
What is a grease fitting?
Machine components which require lubrication will have a small connection, or grease fitting, to which a grease gun can be attached. When the component (such as a wheel bearing) needs lubricant, a coupler on the end of the grease gun hose is attached to the grease fitting. Pressure from the grease gun forces grease through a small valve in the fitting. The grease flows exactly where it is needed, and when the grease gun is disconnected, the valve closes so that lubricant doesn’t escape and dirt cannot enter the fitting.