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Your metal disks are punch outs from electrical junction boxes. They are a mild steel and non magnetic.

It's been a while, but I finally caught back up with this thread.

To answer a few of your questions...

About contacting saw blade manufacturers:
Try contacting Diablo Tools. They have a full...

Not exactly sure of the "burst velocity" of circular saw blade, but I do have access to a 5 HP 12" table saw that runs fine through just about anything, including nails, at 3500 RPM - that's around...

Foot powered lathes before the treadle used a spring pole (usually made of ash in the US) with a piece of twine that ran from the top of the pole, wrapped around the wood to be turned, and then down...

The Shakers of the US invented, patented, and sold a human powered tablesaw a long time ago. It was called a Barnes Treadle Saw.
You can probably download the designs.

Oh and a quick search came...