George Walker made the lovely set of walnut try squares shown above, following the step-by-step instructions in Chapter 4 of “Euclid’s Door.” (I don’t know if he had to refer back to his own writing or not…I know I sometimes do!) If you’re interested in adding them to your tool kit, leave a comment on this post by noon on Thursday, Sept. 21, 2023. I’ll pick a random winner from among all commenters that afternoon, and send them out as soon as I get the winner’s address. Below are the introductory paragraphs to the try squares chapter.
I spent my early years as a machinist in a bearing factory in Ohio. A string of red brick buildings that employed thousands of workers. Making bearings is all about precision and the heart of that was a department called the “Cold Room,” an island kept at 67°F and constant humidity behind a set of heavy double doors. The workers inside wore white shop coats and stood at benches with chrome-plated vises. They were the high priests who guarded that precision. Most of us regular shop rats avoided the cold room if we could. The factory was Africa hot in the summer and stepping in and out of the cold felt hellish. Reluctantly, I paid a visit one hot August afternoon. I’d just bought a precision engineer’s square and needed to get it certified. An engineer’s square has a steel fixed blade made to a high level of accuracy. A bored looking lab technician with tobacco-stained fingers took my square and placed it in a machine called an optical comparator – sort of an industrial microscope that projected the silhouette of my square onto a screen. He slid my square up against the side of a master square, a perfect steel cylinder with a mirror-like finish, and the comparator shined a light beam from behind to measure its accuracy. Any variation showed up as a sliver of light that the machine could magnify and measure.
That was years ago, but when I think about it now, a couple of things stand out. In a modern precision setting, we used essentially the same method to check for square that builders have used for thousands of years. Hold it up to a light and variation shows up glaringly. Secondly, the comparator exaggerated the error through some fancy optics to precisely measure variation from true. In this chapter we will go through the building of a set of wooden try squares and learn some geometric methods to create then test it. We can produce a tool that has an astounding level of precision.