What are Zerks ?
A Zerk or Zerk fitting is a grease fitting or grease nipple.
Why are grease fittings referred to as Zerks or Zerk Fittings?
Oscar Zerk invented the grease fitting, getting the patent in January 1929. So, a common slang term for grease fittings became: ZERKS or ZERK FITTINGS
What are ZERKS used for?
A grease fitting, grease nipple or zerk fitting is a lubrication fitting used to add grease with a grease gun. The fitting is permanently installed by a threaded connection leaving a nipple connection the grease gun attaches to. By using the pressure in the grease gun, grease is added to the system through the grease fitting. Generally a spring-loaded steel ball is fitted to the internal side of the nipple inlet passageway to keep dirt out and the grease in. The ball is almost flush with the surface of the nipple so it can be wiped clean to reduce the amount of debris carried with the grease into the bearing. Grease nipples are commonly made from steel (zinc-plated), stainless steel or brass. Zerks are commonly used on industrial equipment with drive shaft diameters in excess of 20 millimeters, as well as electric motors larger than 5 kilowatts.
Zerks are typically categorized: thread type; thread size and their angle.