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Old July 12th 18, 08:41 AM posted to rec.bicycles.tech
John B. Slocomb
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Posts: 547
Default drill/tap in frames

On Wed, 11 Jul 2018 20:20:25 -0700, Jeff Liebermann
wrote:

On Wed, 11 Jul 2018 15:46:28 -0700, John B. Slocomb
wrote:

(Big Smile) I know a bike builder who accidentally did just that, with
out the rivnut being installed - bending the curve into the front fork
blades with a 5 foot bar :-)


I think that's called a "torque amplifier".

But as an aside, anything will break given sufficient force applied
which doesn't prove much of anything.


Ah, but if there's a significant difference in tension (force) between
the tube with and without a Rivnut, then methinks it demonstrates that
Rivnuts weaken the frame. I think the real trick will be to find two
tubing pieces that are really identical. I'll check with the local
"Bike Church" to see if they have any old frames laying around. I
have a few frames, but I didn't want to trash them quite yet.


Then, of course, the question arises as to what is a significant
difference? Someone mentioned a bit ago about deciding that a TIG
welded frame joint was strong enough to work, ignoring that a properly
made sweated joint is always much stronger.

Bicycle tubes and thus frames, are not all of the same strength.
Columbus XCR material has an ultimate tinsel strength of 1350 MPa
(195,800 PSI), Nobium is 1050 (152,289 PSI) and 25CRMO4 is 80 MPa
(116,030 PSI).

One can only speculate on the effects of drilling, oh say, a quarter
inch rivnut hole in a (approximately) 200,000 psi strength tube and
doing the same thing in a tube roughly half the strength?
--

Cheers,

John B.
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