Machining a Grease Nipple

Zerk fittings are wonderful, all you do is pop a grease gun onto them and pump the lubricant right into where it's needed most! But what if you have a component that has no provision for a grease nipple? What if you wanted to make your own?! 

Our windlass was in need of grease, but to add grease, I was supposed to remove it from the deck, turn it upside down, and pour grease into the casing. This is straight forward enough until you realize that the bolts that hold it down are 20 years old and hidden behind gorgeous joinery! I would spend a lot longer putting things back together once the job was completed. 

Instead, I decided to simply pump some grease into it using a Zerk fitting. The only issue is, it has none! While it lacks the provisions for this attachment, it does have various bolts that thread into the housing and offer access to the inside when the bolt is removed. This gave me the idea to create my own "bolt-on Zerk fitting" by simply boring a bolt and threading in a Zerk fitting.


Using a drill press, I bored a hole down the center of the bolt (or mostly centered). The drill I used was a #7, as specified by the tap that I was using.  


Once bored, I then began tapping the threads into the reamed out bolt. Taps are wonderful cutting tools that are very sharp and need care when working with them. While you might feel inclined to simply screw the tap in, it is important to avoid doing this. You are not "screwing in the tap" but instead you are cutting the threads. The proper motion is to rock back and forth in your turns. Cut an 1/8 of a turn, reverse an 1/8 of a turn, then cut a 1/4 turn, reverse an 1/8 of a turn, cut an 1/8 of a turn, reverse an 1/8 of a turn, cut a 1/4 of a turn, etc.  

This slow back and forth motion will cut the threads while also reducing stress on the tap. Little by little, you will cut your way down the hole and create wonderful threads that you can then use. 


Once the threads are cut, you can then thread in the Zerk fitting. With the fitting connected and secured, all I need to do to grease the windlass will be to thread this into the casing and attach a grease gun! 

This was a redo of a previous attempt where I made a similar product while at a stop in a marina. All I had for tools was a hand drill, a clamp on vice, and a tiny tapper. The end product was functional, but didn't hold up too long. I decided to redo this project with proper tools to create a much better grease administering device.