Out with the old lube, in with the new
A typical grease fitting consists of a bearing surrounded by a rubber sealing system and is fed grease through a zerk fitting. Periodic greasing forces used grease out of the fitting and replaces it with fresh grease free of moisture, dirt and wear metals. It preserves wearing parts by removing contamination and ensuring an adequate supply of lube that has not been subjected to heat and mechanical stress.
Grease guns are capable of producing high pressure because sometimes the old grease has congealed and blocks the flow of new grease into the fitting. The nozzle of the gun has jaws that grab the fitting. Once the gun begins to build pressure, the grease pressure actually gets behind the jaws and helps to hold them tightly onto the fitting.
Doing the job
CLEAN THE ZERK. Road dirt sticks to grease fittings because of trace amounts of grease left over. Unless it is removed, the dirt gets pumped right into the bearing, causing unnecessary wear of both the bearing and seals. So wipe each fitting carefully with a clean rag before you start.
CONNECT THE GUN. Force the nozzle securely onto the fitting. You’ll feel resistance at first. Then the jaws will grab when they pass over the rounded end of the zerk. You’ll actually feel the nozzle click.
PUMP THE GREASE. Begin steadily and slowly pumping the handle on the gun until old grease starts to emerge from the fitting and is then followed by fresh grease. The goal is to purge the contaminated grease and fill the seals with fresh lubricant. n
The Zerk lubrication system used on trucks and other vehicles was invented by Oscar Zerk (1878-1968), a native of Vienna, Austria, who spent much of his life in Kenosha, Wis. He also invented spatter-proof nail brushes, quick-freezing ice cube trays and special brakes for trolley cars.