Using Delrin Tenons

A Delrin tenon is a joint formed by preparing the projection that seats the mouthpiece into the shank from a separate acetal rod and gluing it into the mouthpiece, rather than turning it from the mouthpiece material itself. Delrin is DuPont's trade name for its polyoxymethylene (POM)-based acetal resin; the resin is on record as having entered mass production in 1960.

The material's arrival at the pipe bench is much more recent, and its rationale is not aesthetic but entirely practical.

The Logic of a Separate Tenon

With a tenon turned from the mouthpiece itself, the diameter is left to the maker's hand and the lathe's setting each time; with a ready-made rod, the diameter is known from the start. Because acetal is manufactured to tight tolerances, every rod of a given size is, in practice, the same diameter, so the fit becomes repeatable from pipe to pipe. The second gain is on the repair side: a broken acetal tenon can be removed and replaced with a new one without sacrificing the mouthpiece itself.

There's no binding standard for diameter selection; workshop habit is what decides. A 5/16-inch (roughly 8 mm) rod is most often preferred; 1/4- and 3/8-inch sizes are also used. The decision is made according to the final thickness of the mouthpiece and shank.