the story of Standard Temperature

[Robert Seastrom]

My maternal grandfather was a tool and die man.  I never knew what he was up to during WWII beyond "working on radar", but periodically he would gripe about Whitworth in the context of the war, so clearly he was interopeating with the Brits in some way.  They had their own radar program (er, programme)...

As it happens, I have a fair amount of Whitworth-ish stuff around here and should probably get an appropriate set of wrenches (spanners?) rather than just making do with whatever's close.  The espresso machines are all full of BSP / ISO 228 plumbing.

Hey, I know...  we can sell crescent wrenches that work on metric, SAE, and Whitworth - all in the same wrench!  We'll make millions!

-r


> On Nov 8, 2015, at 7:37 PM, Alex Fraser <beatnic at comcast.net> wrote:
> 
> Well Robert you got me all excited talking about standards.  Temperature and metal size was so important in machining to close tolerances.  I started searching on a parrallel standardization topic, that of screw threads and fineally answered a question I've been wondering about for years.  The P51 mustang was a good airplane, but became a great airplane when mated with the British Rolls Royce Merlin engine.  I wondered if Rolls Royce used Whitworth threads and if they did were the Mustangs equiped with a engine with Whitworth threads?  Well they were!
> 
> Scarfed from http://www.enginehistory.org/british_fasteners.shtml
> 
> Packard Built Merlins
> 
> An often asked question is; “did Packard replicate the British thread system when they built Rolls-Royce Merlins under license during World War II?” The answer is yes; all threads that were used on the Merlin were accurately replicated by Packard. This would include BSW (British Standard Whitworth), BSF (British Standard Fine), BSP (British Standard Pipe) and BA (British Association). Having said that, however, Packard Merlins used U.S. built Bendix injection carburetors; PD-16 for single stage engines and PD-18 for two stage engines, both of which used U.S. Unified threads. British built Merlins employed S.U. carburetors using Whitworth threads. The job facing Packard when they undertook manufacture of the Merlin was daunting to say the least. It’s bad enough having to build a complex product like the Merlin but exacerbating the situation was the fact no tool maker in the U.S. made Whitworth taps or dies. Therefore, Packard were forced into making their own. Although this created a significant hurdle to overcome, the effort was well worth it, Packard and Rolls-Royce components were interchangeable.
> 
> Robert Seastrom wrote on 11/8/2015 11:37 AM:
>> I suppose that we all largely take for granted the notion that 20c is "standard temperature" for most measurements.  But how did that come to be anyway?
>> 
>> A friend recently sent me this:  
>> http://nvlpubs.nist.gov/nistpubs/jres/112/1/V112.N01.A01.pdf
>>  which may be of interest to the folks here.
>> 
>> -r
>> 
>> 
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