What Are Grease Fittings?

Grease fittings by Monroe

Have you heard of grease fittings? They are commonly used on aircraft bearings. Bearings can wear down over time. As they restrict or constrain the motion of the parts with which they are used, bearings will be exposed to friction. Too much friction can cause them to fail. Grease fittings, however, can protect bearings from premature failure.

Overview of Grease Fittings

Grease fittings are threaded endcaps for bearings and similar mechanical parts. Also known as zerk fittings, they are designed to lubricate bearings.

Bearings are parts that restrict or constrain the motion of parts. They are typically exposed to the pressure or load of a part. Bearings will bear this pressure or load while allowing the part to move in a certain way. Grease fittings are simple devices that are used to lubricate bearings.

Bearings often require lubrication. With little or no lubrication, they may succumb to friction-related damage. Grease fittings facilitate the application of lubrication by providing a convenient feed point.

How Grease Fittings Work

You might be wondering how grease fittings are able to lubricate bearings exactly. At the top of a grease fitting is a feed point. The feed point is used to “feed” lubricate into the grease fitting.

You can see an example of a pair of grease fittings in the photo above. They feature a feed point at the top and a threaded connection at the bottom. To use a grease fitting, you’ll need to install it on a bearing. The threaded end of the grease fitting should twist onto the bearing. You can then feed lubricant into the grease fitting via the feed point at the top.

As lubricate enters the feed point, it will coat the bearing to which the grease fitting is connected. Lubricant, of course, will protect the bearing from friction-related damage. It will allow the bearing and the part to move more freely — all while generating less friction.

You can use a grease gun to feed lubricant into a grease fitting. Grease guns force lubricant, as well as other types of grease, through a pressurized hose. After hooking up a grease gun to a grease fitting, you can activate it. The pressurized lubricant will enter the grease fitting before being distributed throughout the bearing.

In Conclusion

If you’re worried about friction damaging or destroying a bearing, you may want to use a grease fitting. Grease fittings are small, simple devices that can protect bearings from friction-related damage.

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