I have always liked technical pictures where at first everything looked static, but then you notice something that is not only perfectly in focus but also perfectly blurred from spinning. Here the central push-rod of a self-tuning headstock is being polished so that its spring mechanism will work cleanly. When the headstock lever is open, the spring keeps the rod extended, else it would rattle back and forth in its channel. The push rod is stainless steel, and you can see a small cross-pin about a half inch from the drill chuck also spinning nicely. And that fine glint off the polished dowel creates an island of purity and precision in a rather busy bench environment.

In this transparent rendering of the headstock you can see the rod and spring running down the middle. The two carbon fiber dowels insert into the neck with a slip fit, and ALL the string tension converges onto the tip of the central push rod where it makes contact with the brass end cap of the neck. It is about 140 pounds of force on just a few square millimeters of contact surface, so do the math and the contact pressure is amplified about 100-fold. The force also converges inside the headstock on the even smaller contact surface between the pushrod and the cam surface of the string tensioning lever. We tried aluminum for the lever, but the contact surface just crumbled.  Steel was too heavy, so we went exotic and used titanium for the lever. Titanium is in a sweet spot with mass and strength just about halfway between steel and aluminum. The stainless steel dowel works well with the titanium lever as long as the contact surfaces were very well polished and you put a Q-tip dab of lithium grease in there every now and then when the lever is open and the contact surfaces are exposed.

The 3M 401Q wet-or-dry sandpaper starts at 1000 grit and goes up to 2500 grit. Here I think 1200 grit is being used, and the water drops on the granite bench slab show it is definitely being used in wet mode. To the lower left looks like a piece of used 400 grit sandpaper used in dry mode at the beginning of the polishing process. Going clockwise from there around the zoo, there is the snout of a vacuum cleaner, an overloaded electrical outlet, a small bag of unknown screws from the hardware store, our friend Bondo, a measuring tape, a 20-year old roll of duct tape that just won’t leave, miscellaneous drill and Dremel bits and brushes, something being protected under a white plastic trash bag that I have no idea what it was, a half-pint jam jar with something green in it, Stew-Mac spray lacquer, black spray paint, super-glue accelerator, and the plastic lid of a small mold resting on a significantly newer roll of masking tape.

The granite slab in the shop provides an easy-to-clean and perfectly flat work surface useful for any number of activities. Granite slabs typically cost hundreds of dollars and weigh hundreds of pounds if you get them through legal channels. The one on the bench here was an orphan I found during one of my regular visits to the scrap pile out behind a stone countertop shop a couple of towns over. When these shops cut off the end of a slab to make a countertop the right length for a customer’s kitchen, the cut-off piece is usually broken and then tossed on a pile out back. But every now and then you get lucky (there are other vultures keeping an eye on the same scrap pile), and you can get a nice big piece like this one. It is about thirty inches square and an inch and a half thick, with one side polished like a mirror.  It turns out that the polishing process used by the manufacturers of stone countertop slabs leaves the surface perfectly flat down to a few microns, which for all intents and purposes is just as good as the legal kind, and you don’t need a forklift to move it.