The Home Machinist!

Still available. For example, using "push drill" or "archimedes drill" as search string on Amazon... https://www.amazon.com/SE-849PDS-Spiral-Drill-Spring/dp/B001HBY8KE/ref=sr_1_2?dchild=1&keywords=archimedes+drill&qid=1622568814&sr=8-2 https://www.amazon.com/KATUR-Sem...

Yes, my apologies; I forgot that the pictures were not of the OP's engine. The point of checking the valve mating is still relevant.

... Finally, you definitely don't want to heat the cylinder intentionally. The engine works because the hot gas from the flame contracts when it gets cooled by the (relatively) cool cylinder. On my two homebuilt flame eaters I must preheat the (aluminum) cylinders and (steel) valves to get them sta...

Were it not for Caribbean pirates, we (Usonians) would be using the metric system today. Thomas Jefferson, arguably our most intelligent president, when secretary of state under Washington, realized the need for a single, sensible measurement system for the USA. He attempted to introduce the metric ...

... Another interesting thought. We often discuss imperial versus metric. The US has held steadfast with the Imperial system, but then, has it, really? The US gallon is not the same as the British gallon. Are they both considered Imperial?... The system used in the USA is termed "US Customary ...

Center square for finding center on end of cylindrical stock

Center finder for finding center on edge of rectangular stock

Plans for both can be found here...

https://www.homemadetools.net/forum/27- ... ders-82451

...I keep the constant in my head----a mm equates to .03937". None of these are exact but close enough for what most folks need... It's particularly easy to mentally multiply by a number of the form x.x This makes two common metric to inferial conversions easy. There are 2.2 pounds in a kilogr...

I'm not sure if you need to join the forum to see these hammer plans; even if that's the case, it's a great forum and a copious source of plans for all manner of DIY stuff...

https://www.homemadetools.net/forum/51- ... lets-84318

... If you must add water, be certain to add the acid to the water, all the while stirring constantly. ... The mnemonic rhyme I learned was: Add acid to water Like a fella oughter It's been decades since I worked with acid but the rhyme sticks in my memory. That's probably why, in the days before w...

You're comparing to the current, conventional uses for gears. Better to think about applications where the unique aspects of the design are useful. For example... Gears that can work through a thin plastic/glass sealing/isolating membrane - think food processing, medical applications, space-based de...

Electronic racks are one place they are used...

https://www.racksolutions.com/news/data ... explained/

I believe some old woodworking equipment, e.g. planes, used that size for adjustment screws but I'm not a woodworker so take that with a grain of salt.

How about old-fashioned hand layout? Draw a circle of diameter 'D' on your stock, then set your dividers to a chordal length 'C' given by:

C = D * sin (180 / N) ; where N = number of divisions

and use them to strike off N points on the circle.