On Mar 20, 4:58*pm, Doug Hoffman wrote:
Bob Kuykendall wrote:
On Mar 19, 6:08 pm, Doug Hoffman wrote:

I just wish the US would perform its conversion to metric units for
*everything*. *The sooner the better. *But that job is being handled by
our highly efficient government. *Don't hold your breath. *:-)

Kind of a hijack, but what I wish is that aircraft hardware
manufacturers would get their crap together and produce a coherent
metric equivalent of the AN system of common aircraft hardware.

The magic of the AN hardware system is not that they offer any
particularly high strength (they don't; for the most part AN bolts are
equivalent to Grade 5 hardware store bolts) or any particularly high
precision (again, they're about the same as the bolts at Ace or True
Value). The magic is that AN bolts have just enough thread for a nut
and somewhere between 0" and about 0.125" of washers, and that they
come in length increments of 0.125". Those two elements let you create
a nice, tidy bolted joint of virtually any practical grip length, and
not have the threaded portion of the bolt loaded in shear, and not
have a bunch of threads hanging out of the nut. Furthermore, common AN
hardware is very attractively priced, for the most part you can buy
them from any of several aircraft parts outlets at the same or even
lower prices as Grade 5 bolts at a mom&pop hardware store.

By contrast, metric aircraft hardware has no coherent system of
markings, thread lengths, and grip lengths. It averages twice or
thrice the cost of AN hardware when you can find it, and is available
from only a few outlets. When you need a replacement bolt for your
European aircraft, you have virtually no choice but to order it
directly from the manufacturer at huge markups and with huge shipping
charges.

I like the metric system, and I like metric hardware. I appreciate
that even American cars are, by and large, assembled with metric nuts
and bolts these days. But given the choice between about $500 worth of
AN hardware per aircraft and twice or thrice that in metric nuts and
bolts that offer no greater utility, hmmm, I think I'll go with the
less expensive option.

End rant.

Hi Bob,

Yes. *There may be some niche areas like aircraft hardware that would at
least require legacy support for a period of years. *Makes me wonder
what Boeing/Cessna and others are doing now and plan to do in the future
in that respect.

Regards,

-Doug

Btw, American designed cars and trucks do more than just assemble with
metric fasteners. *Nominal dimensions are typically, e.g., 100 mm for a
bracket width instead of 4.0". *We call that "hard metric" design. *Some
user interface items like wheel lug nuts may still be SAE.- Hide quoted text -

- Show quoted text -

While we're 'Ranting'.... Bob, that would be nice, wouldn't it? It
took me 2 tries to get the right bolt from Grob when I went throught
my control system a few years ago.
DON'T get me started on US auto makers. I have two Dodge Trucks. I
HATE the fact that evey time I get under one to work on it, I need to
take BOTH metric and SAE tools. Pick a STANDARD! My favorite example
was an exhaust stud on a 1998 Olds Intrigue. Engine side - SAE
exhaust flange side - metric.
Rant off.
I feel better now.