How a grease gun works

Updated July 19, 2017

Grease guns are used to lubricate joints and connections that require re-greasing periodically. The grease gun is a portable device that stores a determined amount of grease. The grease is then pressurised, even slightly sometimes, to pump a concentrated amount of grease from an aperture located on the end of a small hose. The hose is flexible to allow maneuverability in situations where the grease fitting; also knows as a zerk fitting, is placed in a compromising position. Grease guns are found in every reputable repair shop. Most cars used to have multiple zerk fittings on the chassis components and driveshafts. Many newer import and domestic vehicles are now being manufactured with sealed chassis components that do not require greasing. However, once the components fail, the aftermarket replacement of the component most always is supplied with a zerk fitting.

Grease guns are hand-held. Most of the economic ones use a cartridge of grease inserted into the chamber of the gun. Installing the cartridge correctly will make less of a mess and ensure the grease purges out of the aperture correctly. The spring-loaded plunger on the bottom of this type of gun is pulled back and locked in an open position on a slot located at the bottom of the chamber. The top of the grease gun where the trigger and hose attachments are located is then unscrewed from the chamber of the gun. Removing the plastic cap of the cartridge will reveal the grease inside it. This is placed into the chamber grease side down. At the other end of the cartridge, now visible at the top of the chamber, is a flip top can lid. This is removed and discarded. The top of the gun is then screwed back onto the chamber tightly. A few hand pumps of the trigger or lever will prime any air pockets in the cartridge and a small amount of grease will purge from the aperture at the tip of the flexible hose. Each pump of the trigger will produce a small amount of grease.

What Grease Guns are Used For

Grease fittings or zerk fittings are located on many light to heavy duty trucks and SUVs. Some cars are still manufactured with grease fittings on the chassis components. Large commercial trucks have several zerk fittings located throughout the chassis, U-joints, driveshafts and other places that require lubrication. Lawn and garden tractors that use a pinion steering system may have tie rod ends and ball joints with zerk fittings requiring occasional grease. Mower decks for riding lawnmowers often have zerk fittings on the individual arbors of the deck. Industrial equipment for factories often have zerk fittings for machinery used requiring scheduled grease applications.

Different Types of Grease Guns

The most common grease gun is the hand-lever style for its economical price. This type can be more difficult to operate however, because the aperture on the tip of the hose on the grease gun sometimes requires pressure applied (by hand) to the zerk fitting in order to properly pump grease into the fitting. The hand-lever style requires one hand to hold the chamber of the gun steady while pumping the lever with the other hand, leaving no hands to apply pressure to the aperture. A finger-trigger or hand-trigger type grease gun is a better alternative because you can hold the gun and then squeeze the trigger with the same hand while using your opposite hand to apply the necessary pressure to the aperture on the zerk fitting

Another less popular style grease gun uses a manually pressurised chamber without a trigger or lever apparatus. The placement of the aperture onto the zerk fitting releases the pressure and purges grease into the fitting.

Some grease guns use pneumatic pressure instead of the manual spring-loaded plunger. This type is found in shops that use air compressors for their equipment where a lot of grease is used. Often times, the grease provided to the guns is stored in large barrels and the air compressors apply the pressure from a pump placed at the top of the barrel, through a pneumatic hose and into the gun. Pulling the trigger of this style gun will continuously pump grease from the aperture until the trigger is released.

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About the Author

Jody L. Campbell spent over 15 years as both a manager and an under-car specialist in the automotive repair industry. Prior to that, he managed two different restaurants for over 15 years. Campbell began his professional writing career in 2004 with the publication of his first book.