On Fri, 13 Jul 2018 12:18:26 +0200, Emanuel Berg
wrote:

John B. Slocomb wrote:

Is it more thick at the bottom of the bottom
bracket shell and at the bottom-mid section
of the down tube where I have seen this
numerous times, and also the chainguard
stays to the chainguard intersection?

A bottom bracket is usually specified as 7 -
8 mm thick.

And the mid-bottom part of the down tube?
The screws are interchangeable in size
and length.

Well that depends. Probably on the cost and class of the bike. The
down tube is pretty thin on most better class road bikes. Say Perhaps
..6 - .7 mm in wall thickness. Depending on whether it is butted, non
butted, etc,

Yesterday BTW I saw a second bike with the
exact same configuration. The bracket is bent
so it is round along the tube surface, but what
holds it in its place seems to be a single M5
screw with a flat PZ2 head.

Given that all the pedaling torque passes through the bottom bracket
I'd doubt if a new bike would use a single screw to hold the BB onto
the frame tubes.

--

Cheers,

John B.