There are several different types of grease fittings. They are the hydraulic (Zerk fitting), the buttonhead pin, and flush type of fittings. See figure 3-14. The two most commonly used fittings in naval aviation are the hydraulic- and flush-type fittings. These fittings are found on many parts of the aircraft. 

HYDRAULIC FITTINGS. This type protrudes from the surface into which it is screwed, and it has a rounded end that the mating nozzle of the grease gun grips. A spring-loaded ball acts as a check valve. Figure 3-14 shows across-sectional view of a straight hydraulic

Figure 3-14.Types of lubrication fittings.













Figure 3-15.Lubrication chart.

fitting and an angled hydraulic fitting made for lubricating parts that are hard to reach.

FLUSH FITTINGS. This type of fitting sets flush with the surface into which it is placed. It will not inter-fere with moving parts. Figure 3-14 shows a cutaway view of a flush-type fitting and the adapter nozzle used on the grease gun.