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Old July 11th 18, 03:42 PM posted to rec.bicycles.tech
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Default drill/tap in frames

On 7/9/2018 11:16 AM, David Scheidt wrote:

he was also wrong about many things. Every bike I've ever had has had
holes drilled in it. Clearly, there is a range of holes that do not
cause failure, and some that do. The question is where does a rivnut
fall? I wouldn't drill a 5 mm hole a on 26mm diameter tube, but they
work fine on large diamter ones.


Did you drill those holes and install the Rivnuts or did they come from
the factory that way. Were these steel or aluminum tubes?

Rivnuts in very thin tubing need to be installed very carefully. Drill
them with the wrong drill and you'll crack the tubing. Install them too
loose and they'll spin. Install them too tight and they cause cracking.

You can get away with doing this but it doesn't mean that it's a good
idea. There's a reason why all the experts advise against doing this,
and why it voids the frame warranty (if you're the original owner with a
lifetime warranty, you might worry about this).

For those determined to do this, look into the Plusnut (made by Rivnut)
which is more suitable for end-user applications.

For the OP, is the chainstay even a large enough diameter for a Rivnut?

What might work is using M3 x 0.25 screws. You'd have enough threads for
a 1 mm thick tube. Both the screws and the taps are not cheap as these
are used on high-precision machinery. Tthey also have M6 x 0.25, but I
did not see any M5.




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