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On Thursday, April 2, 2020 at 4:26:16 AM UTC-4, John Doe wrote:
Michael Terrell wrote:

I've cut them with a fly cutter.
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ah. A 40mm bearing housing...............

I would use a magic marker on the aluminum and then scribe a 40mm circle
where you want the hearing. Then use about a 1/4 inch drill to chain drill
most of the hole and then finish with a round file . No suitable file,
then buy a 3/4 inch dowel and use it with sand paper. With good lighting
you should be able to make it close enough to have a press fit.

Dan

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http://www.wright-brothers.org/Infor...903_Engine.htm
"The crankshaft was made out of a block of machine steel 6 by 31 inches and
1-5/8 inch thick. I traced the outline on the slab, then drilled through
with the drill press until I could knock out the surplus pieces with a
hammer and chisel. Then I put it in the lathe and turned it down to size and
smoothness."

Before milling machines became common machinery builders had to be VERY
skilled with saws, chisels and files. Look at antique clocks, weapons and
armor to see how good they were.

Lathes are much older, as in ancient Greece. Foot pedals or an apprentice or
slave turned them while the artisan carved the wood, ivory or metal with
hand-held chisels, like we still do on a wood lathe.
http://www.wallswithstories.com/anci...furniture.html
"By the 6th century BC, the Greeks had most of the possible hand tools for
designing wood €“ the adze, ax, saw, plane, hammer, rule, and lathe."

This is what they could make with their hand tools:
https://en.wikipedia.org/wiki/Antikythera_mechanism


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