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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. |
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