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Lathe builders in 1805 didn’t know Roger Davis. They’d just have a blacksmith make them a simple crank and be done with it. I didn’t know Roger either when I built my lathe. He saw the blog entry showing the (pathetic) wooden crank I made, in the absence of a blacksmith, and suggested it wouldn’t last long. It didn’t. He then made me one that will never fail. It is solid!
Roger Davis is a fellow Hoosier with the good sense not to move to New York, a frequent visitor to the Sawmill Creek forums, owner of “a very complete machine shop” and self-proclaimed “lack of good sense,” an aerospace engineer by education (Yay Purdue!), former high school teacher (physics, cemistry, algebra), a builder of scientific instrumentation (start to finish) as his paying job, a builder and user of muzzleloaders as one of his hobbies, and variously proficient in gunsmithing, blacksmithing, woodworking hand tools, A&C furniture, cooperage and who knows what else. Bottom line: a generously good guy.
Photos and a drawing tell most of what you need to know to make one. If you have the metal working equipment to cut a block of steel, cut a slot in it, drill accurately, and tap some screw holes, you can make one similar. For what it’s worth, the distance between pivots was simply an estimate (a little more than a tenth the diameter of the flywheel) and has worked very well. Roger didn’t specify the size of the cap screws, but they look to be 1/4 by 20 by 1 inch long. The only other thing not shown on the drawing, that’s very visible in the photos, is a dowel pin that retains the crank pin. The retaining pin is probably not needed on this particular crank since Roger built it to such close tolerances that the crank pin probably took several tons of pressure to seat as a “press fit.”
When installing on the flywheel axle, be sure to go back and forth between the two screws, as they each affect the other’s tightness until they are really tight.
This crank has been very solid. I’ve got hours and hours of use on the lathe and ZERO, Nada, NO slippage from the crank. It simply works! Thanks again, Roger.