¼” x 28 threads include ¼” x 28 SAE-LT, Special Taper (Thread Forming) and ¼” x 28 UNF.
SAE-LT stands for Society of Automotive Engineers – Lubrication Thread.

Grease fittings or zerks with ¼” x 28 SAE-LT threads have a UNF thread form but with a 1:16 taper to ensure an optimal seal in a ¼” x 28 UNF tapped hole. Reference SAE J534.

The tapered thread is preferred as it negates the need for additional sealant and is less likely to become loose under vibration.

The self-forming version has a 90° thread form and a 10° diametral taper. Both these threads are unique to grease fittings.
UNF has a 60° thread form and is parallel.

These grease fittings are designed and manufactured from high quality materials at our site in Leeds.