On 8/22/2019 7:19 PM, Frank Krygowski wrote:
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.


I think Tom (correctly) noted that a V-brake anchor is more
shaped like an 'internal wrenching bolt' (a term he likely
knew from USAF service long ago) than a standard DIN 912 cap
screw.

They are not the same thing, but the general appearance is
similar.

Arguments after that seem contrived to me. Clamping on a
3mm hardened anchor plate means the head shape is
irrelevant. As you note a regular DIN 933 bolt works as well
as a DIN 912 cap screw.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971