On Fri, 09 Mar 2018 07:54:47 +0100, Emanuel Berg
wrote:

AMuzi wrote:

Aluminum is no good for a bike frame because
it's too harsh and stiff. Aluminum won't work
either because it's too soft and noodly.
That went on just forever with, as always,
much digression.

One on-topic question on aluminium/aluminum
I thought about asking is how do they cut the
pipes so to get those roundish forms so that
for example the top and down tube aligns so
well with the head tube?

1. You can cut and file the tube end to fit with hand tools, or

2. You can set the tube up at the correct angle, using a vertical
milling machine, and cut the tube end to fit using the proper size
end mill, or hole saw,.
See
http://www.instructables.com/id/Build-a-Bicycle-Frame/
Tube Mitering
--
Cheers,

John B.