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Old July 14th 18, 02:14 AM posted to rec.bicycles.tech
Ralph Barone[_4_]
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Posts: 853
Default drill/tap in frames

John B. Slocomb wrote:
On Fri, 13 Jul 2018 12:49:33 +0000 (UTC), Ralph Barone
wrote:

John B. Slocomb wrote:
On Fri, 13 Jul 2018 00:10:02 +0200, Emanuel Berg
wrote:

James wrote:

Then you should definitely not just drill
and tap the frame tube itself.

Why not?

The material is too thin.

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.
--

Cheers,

John B.


Maybe 3-4 mm. Are you quoting the difference between the OD and ID, or the
wall thickness?


I just looked at their catalog which red, for example:
"LB100R - For 22.2mm Chainstays. 60.30x62.30x7\ufffd.
No guides or cut-outs".
or
"LB109R - With Oval 30x17mm. Chainstays.
Angles 60x64x7.30\ufffd. No guides or cut-outs."

Given that the first two numbers were obviously length and breadth
assumed the last was thickness. Not so?

--

Cheers,

John B.


I don't know. I just thought that 7mm wall thickness for a bottom bracket
shell appeared to be overkill to me. I did some web searching and nobody
publishes data on the OD of bottom bracket shells (probably because it
doesn't matter to a first approximation). However, looking through a bunch
of diagrams, I did see that many of them had a 7mm deep pocket to hold the
bearings. Perhaps that's where your 7 came from.

Aha! This BB shell has a 38 mm OD and a 1.370" ID, which gives about 2mm
wall thickness.
https://framebuildersupply.com/produ...od-made-in-usa
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