A flakey wire gauge is a problem if I am making one Merlin engine. If for some reason, I am making perhaps 55,000 engines, I can amortize some tooling. I also know what space the spring fits in. I can work out the performance of the Rolls Royce spring, and I can design a new spring that uses American gauges, and fits in the Rolls Royce space.
Your spring will now only be interchangeable if the mating parts are changed as an assembly and then there is the problem in the overhaul shop how do they work out (without fine tolerance measuring each spring) if it is an brand A or brand X spring, keeper and base ring that they need to replace. From your background you know the problems that will quickly arise if a fractionally oversize valve spring is fitted to standard size mating parts (or standard spring to undersize mating parts). And remember that they must be interchangeable with every other part number x spring used on that series engine. EG the Rolls Mk 24 and Packard 224 (and a couple of other models) have maximum interchangeability).
If I design trucks, tractors and combine harvesters, I am going to have problems re-engineering guns.
The American contractors did not re-engineer the Hispanos. They just built them straight off the first angle Brit drawings using third angle interpretation which is why then ended up mirror image.
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I agree that British Standard is an Oxymoron as is the concept that the US were any better at that time. AC, AN, NAS, Parker hydraulic fitting were in use in aircraft prewar and early war and those have a wide range of thread types and mating angles etc etc etc and interchangeability is almost non existent without changing the pipe/hose simultaneously. And the component end of those fittings can have short or long tapered or parallel threads with makes life even more "interesting" for the poor suffering repair man. And the US had many different gauges for sheet and wire.
Likewise Metric was a mess pre ISO.
I refer to the BS and US standards as using inFerial measurements from joining
inferior with imp
erial.
On the nuts and bolts side of things, with one exception in the common sizes, the US National Course and Brit Whitworth thread have identical threads per inch but different thread angles and thread forms. This made it possible to fit US nuts to UK bolts and vice versa but that naturally caused hardware failures. The US and UK worked hard on solving that problem and created Unified thread using the best features of each thread. Whitworth was declared inactive for new design in
November 1946 and disappeared from British mass production in the very early 50s. I do not know the US dates but for them the change was easier as Unified used the American head sizes and tools.
Australia, which has officially been metric for decades, not only still uses large amounts of Whitworth but recently goods have begun appearing which have what is called a 13mm bolt. Naturally, when you measure it up, it is nothing more than a rebadged 1/2 Whitless.
No respected tool manufacturer has made Whitworth spanners for many years so that means you must use a loose fitting real metric or inch spanner or the good old Aussie UNF spanner - NO, not a Unified National Fine spanner but a Universal Nut F...er as shown below.