Making stems!
My schematic for the stem I'll be making.
The stem. Attached to the crown of the watch, it's the connection from you to the movement within your watch. Composed of cylinders, flats, notches, and a threaded section; most stems have multiple points of interaction. This means the shapes and sizes must be right, this is a high torque part that receives frequent use. A misshapen stem will grind pieces or get ground away, introducing dust into your movement-and that's a bad thing.
My stem secured in a lathe.
There are lots of little details and an order of operation to follow when making a stem. If you look closely at the squared section you'll see that the ends and the corners are round and not coming to a sharp edge. This is so your stem can easily find its way through the sliding and winding pinions, as well as the other holes it needs to maneuver. Additionally, sharp corners in this situation would wear over time and eventually give way to metal shavings and dust (please no).
Cutting the slots and steps necessitate right angles. If, for example, the slot is not cut nice and perpendicularly then the set lever will slowly grind the angled edges until they are...
MONSTER STEM!
Before making the stem for the 6497 we made some stems out of brass that we scaled up multiple times. While large pieces have challenges independent of small pieces (and vice versa) this was to help us establish a good order of operation and visualize the different features of the stem-which to a novice, some of the smaller edges and steps may go overlooked.
Stem with some polishing compound on the threads
For the 6497 stem you want to cut as much of it as possible before hardening and tempering it. Working hardened steel is much more challenging and necessitates different tooling than raw steel. Since the stem is such a small and detailed component it's very easy to break, especially when cutting the slot out. The quenching after heating for hardening is one of the more challenging aspects, if your quench technique is off or something happens and you don't quench your stem straight up and down, it'll warp - and your stem will be rendered useless.
Bringing the stem to a polished finish is also essential, polished surfaces that are interacting with other parts will wear less, have less friction and as a result, last longer. Above you can see my stem with polishing compound on the end of the threads, I'm about to thread it into a piece of wood with a tight hole to try and polish all surfaces of the threads. At this step I will make any final cuts necessary, make sure my surfaces are flat, edges are 90º and everything is polished.
A fun exercise with skill training that transcend the fabrication of stems, though, for a days work I'd probably end up paying $6 for a replacement stem ;) .
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