On 8/22/2019 7:05 PM, John B. Slocomb wrote:
On Thu, 22 Aug 2019 17:22:20 -0500, AMuzi wrote:

On 8/22/2019 4:46 PM, Tom Kunich wrote:
On Thursday, August 22, 2019 at 10:21:26 AM UTC-7, Chalo wrote:
AMuzi wrote:

Tom has a point in that most linear ("V") brake anchors do
not
have cylindrical heads and actually do look more like an
'internal
wrenching bolt':

Tom misses the substantially more important point that you won't find an "internal wrenching bolt" with metric threading, and that functionally the thing that fixes a V-brake's cable is a metric socket head cap screw. Just as a brake pivot bolt is usually a button head socket cap screw whether its head is domed or conical.

Not to be too critical - but it is the HEAD shape that is critical. As all of the illustrations that Jeff published shows - they are available in any threads. Can you explain to me exactly why you believe that the THREAD is what makes an internal wrenching head?

You're sounding more and more like Frank every day. He doesn't even understand that the difference between a taper head screw and a cap screw is. You're joining his club I see.


I have to admit I had never heard the term 'internal
wrenching bolt' until you wrote that.

Given the high profile disasters from counterfeit fasteners
sold to the Air Force and the required specification for
same (material, fit/finish tolerances, plating, hardness
etc) I could well imagine that USAF simply made up a
distinctive head shape to keep stray hardware out of their
system, keep engine mounting bolts separate from brake
system bolts and so on. I don't know that, but it's not
unreasonable.

I hadn't known about the faulty fasteners. But when I was in the A.F.
there was a whole section of the Navy, A.F., and likely the Army, that
spent it's time determining and certifying that the proper bolt was
used in the proper place.

But, of course, they did this from the
"standards" marking on the bolt itself :-(

By the way, Caterpillar Tractor was very perturbed about falsely
marked "CAT" bolts that were being sold in Singapore - that were
actually manufactured in Italy.

We became involved as we had done a rebuild on a Caterpillar 6
cylinder engine and it was impossible to torque the head bolts. You
kept turning the wrench and the bolts kept stretching :-)

I suspect the unusual head shape of genuine military Internal Wrenching
Bolts is primarily to help insure the bolt strength and its
head-to-shaft radius are within specs - that is, to help prevent the use
of a sub-standard fastener in a critical application.

Of course, that doesn't mean every fastener with that head shape will
have those same properties. Companies can produce whatever part they
want for use on their own devices. And derailleur clamp screws are
certainly not ultra-strong or highly stressed. I've replaced stripped
ones with garden variety metric screws and had no issues.

Tom refuses to say what he's imagining about pressure on the washer, but
I think any such imaginings are fantasy. Unfortunately, I don't think
he's got the background to competently discuss that aspect.

--
- Frank Krygowski