Mick56
Well-known member
I have this Hinsdale SRA-1- socket in 1/2" square drive, but what is it for? An ebay seller says its for a Alemite Grease Fitting, but I couldn't find a fitting that would need a socket like this.
Pin-type Alemite fittings are a cylinder with a cross-pin. The fitting on the grease gun is slotted to engage the cross-pin and lock the two together. They were used on early motorcars and industrial equipment. They were replaced by ball-type Zerk fittings in most applications.
It looks like your socket is used to screw in/out the pipe threaded fittings by engaging the cross pin with two of the slots. Most of these fittings also had a hex below the cross-pin, and folks used an open-end wrench to remove/replace them.