Stem Work

Stem work is the job of turning a solid vulcanite or acrylic rod into a finished piece that can be fitted to a pipe. In a handmade pipe, the mouthpiece is not an accessory independent of the bowl but the second half of the airway: its cross-section, the thickness of the end that enters the mouth (the bit), and the course of the channel inside it determine draw as much as how the bowl itself is carved. For this reason mouthpiece making is considered not a cosmetic but a functional stage, and is often cited in workshops as the section that takes the most time.

Material and Raw Form

Mouthpieces are either obtained from solid rod stock or worked from a molded blank. Vulcanite — rubber hardened with sulfur (ebonite) — remains common in handmade pipes because it sits soft against the teeth; however its surface oxidizes over time and requires regular care. Acrylic does not oxidize and keeps its color, but is harder and more brittle. A detailed comparison of materials can be found in the mouthpiece materials entry.

Obtaining the Tenon

The part that seats the mouthpiece into the bowl is the tenon, which enters the mortise. The tenon is obtained by one of two routes. In the classic route the mouthpiece is mounted on a metal lathe and the tenon is turned directly from the mouthpiece's own material. In the second route, the end of the mouthpiece is drilled and flattened, and a separate Delrin piece is fixed into the opening. Delrin, an acetal homopolymer introduced by DuPont in 1960, is tougher, more resistant, and lower-friction than vulcanite and acrylic; these two properties make it the preferred choice at a joint that is frequently taken apart and reassembled. For details of the practice, see the use of a Delrin tenon entry.

Some makers prefer to let a freshly drilled bowl rest for a while before taking the tenon measurement. The reasoning is that the socket shifts dimension slightly with ambient humidity and temperature, so a measurement taken after this settling has finished holds up better over time. The resting period is a personal preference that varies from workshop to workshop.

Shaping and Finishing

The rod is first brought roughly close to its final shape; sanding drums and open-center grinding discs are used at this stage. Machinery can bring it quite close to the final form, but the real work begins by hand: the roughly shaped mouthpiece is reduced to its design with files, then run through progressively finer sandpaper until ready for polishing. Throughout, wall thickness must be constantly watched so as not to break through into the air channel.

The end that enters the mouth is where differences of less than a millimeter are felt; this is why the final workmanship is considered the longest and most exacting stage of the whole process. Bent mouthpieces are heated and brought to the desired angle. For the ring and transition pieces fitted at the end facing the bowl, see the stem inserts entry; for the operations on the bowl side that complete the process, see the drilling on the lathe entry.