The vast majority of airframes and powerplants use U.S. standard/SAE hardware. Which manufacturers of engines and airframes use metric hardware?
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I believe there was a hardware spec used in Europe called ASN that was metric and was used in some European GA airplanes. – John K Oct 09 '18 at 20:54
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Related: Are an aircraft's nuts and bolts generally either all Imperial or all Metric, or can they be mixed? – fooot Oct 12 '18 at 21:25
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@fooot thanks fooot. I’m aware of this post and have read the whole thing. While some good points are made, it doesn’t really answer my question... only a few examples are given. – Pugz Oct 12 '18 at 21:26
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You mean imperial measurements vs metric? RR use both, depends on the engine. – Notts90 Oct 13 '18 at 09:51
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@Notts90 some use US standard, some use imperial, but I am specifically interested in who uses metric. – Pugz Oct 13 '18 at 12:54
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@Pugz none of the big western manufacturers are exclusively metric but RR does use metric for all new engines. The most likely to be exclusive are Russian manufacturers. – Notts90 Oct 13 '18 at 12:59
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@Notts90 thank you. Even if it’s not exclusively metric, but some metric, I still want to know about it. – Pugz Oct 13 '18 at 13:00
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All use metric dimensions, only the numbers look sometimes rather odd.
This statement is more serious than it might look, in some places you order parts in metric dimensions and they come as 3.175 mm or 12.7 mm.
All Russian (and, by extension, all former East Bloc country) engines use metric dimensions. You only see fewer of them.
I am less sure about French engines like the CFM-56 which uses a GE-designed hot section, but the fully French-designed engines use metric, too.
In the GA world the modern Diesel engines are all metric.
Peter Kämpf
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Can you please elaborate on what you mean by “all use metric dimensions”? I’ve been working on several power plants and airframes - Cessna, Piper, Grumman, Beechcraft (King Airs), P&W PT-6 turbines, Lycoming, Continental, and all seem to use SAE only dimensions and fasteners/hardware. – Pugz Feb 01 '19 at 17:44
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1@Pugz: OK, you didn't get it. Use a metric caliper. Measure some dimensions. You will get metric dimensions, right? Even from a US engine. – Peter Kämpf Feb 01 '19 at 23:23
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Lol that’s funny. I kind of thought you were saying that but didn’t take it seriously. Nice joke. – Pugz Feb 02 '19 at 00:26
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1@xxavier: Yes, you are right: The imperial units are defined by the corresponding SI units. Therefore, the inch is now defined as 25.4 mm. Want more precision? OK: 1 inch = 25.400000000000000000 mm. Therefore, all dimensions are metric but with odd numbers. This joke has more depth than appears on first reading. – Peter Kämpf Feb 02 '19 at 08:31
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2@PeterKämpf Well, yeah :)) - Then again it's rather shallow, not really working so simple, as metric bolts are made to ISO pitch/lead while 'imperial' bolts are defined by the ANSI maintained "Unified Inch Screw Threads Standard".So while a 3/8 bolt does measure about 9.5 mm, a 9.5 mm nut won't run along. Diameter is just one of 6 major (and mord than a dotzend secondary) values to describe such a simple piece :)) And yes, it's relevant, as the OP asked for SAE specifications. Standards include way more than just the way length is counted. – Raffzahn Feb 02 '19 at 16:15
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@Raffzahn: You need to stay consistent, of course. Taking diameter from ISO and thread pitch from SAE won't work. And there is no such thing as a 9.5 mm nut, at least not in the standard ISO sizes. – Peter Kämpf Feb 04 '19 at 18:26
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@PeterKämpf Well, almost, as there are not standard sizes given, just recomended much like in the prior DIN standards That's as well a difference between ISO and SAE, as the later only defined discrete sizes. Also, not really woth to argue about an example size when it's about the underlaying mechanics, isn't it? – Raffzahn Feb 04 '19 at 18:41
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This is all great trivia, but I was already aware of this and it’s not particularly helpful pursuant to my original question. The fact that the inch is in actuality defined by a metric value is not helpful in answering my question. Any actual answers? Tools are not specified in such a way, and I’m pretty sure you know what I’m actually asking :-) – Pugz Feb 12 '19 at 01:20
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@Pugz: So you think that Russian or Chinese or French engines also use imperial units? If you can't handle a honest answer, why do you ask in the first place? – Peter Kämpf Feb 12 '19 at 05:21
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@PeterKämpf Airbus uses mostly SAE hardware on their airframes. Of course the commies use metric. I would prefer everyone use metric. But they don't. In the non-communist world (most of the world) most companies use SAE or Whitworth on aircraft, because of the historic aircraft tooling being in inches after the fall of Hitler's Europe and the growth of the aviation industry in the west that outpaced the growth in the east. This answer falls short of helping me know who uses metric hardware (bolts,screws, nuts, etc.). I would appreciate some guidance of which manufacturers use this. Thanks! – Pugz Feb 12 '19 at 11:16
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@Pugz: In my flying club we use both - the Rotax and Limbach engines of the motor gliders have metric parts while the Lycoming on the tow plane has tools in imperial units. I tried to give you a rule to determine who uses what; an explicit list would be rather long. – Peter Kämpf Feb 12 '19 at 17:13