[modeleng] Re: coarse threads

That is an odd one, I think they both use the same basic geometric
progression for choosing TPI it's just that the half-inch is on the
boundary (ie the progression says it should be 12.5) and Whit chose
12TPI while UNC opted for 13, I know I'm glad that 1/4 and 3/8 are the
same cos I have to  make camera fittings for work sometimes and
according to my gauges camera to tripod-head mounts are a mixture of 1/4
Whit and 1/4 UNC while tripod to tripod-head fittings are normally 3/8
UNC as far as I can tell.... That said I see UK, Italian and US sourced
camera mount plates but only normally Italian tripods.....
chrisc

-----Original Message-----
From: modeleng-bounce@xxxxxxxxxxxxx
[mailto:modeleng-bounce@xxxxxxxxxxxxx] On Behalf Of
john.burridge@xxxxxxxxxx
Sent: 28 January 2007 10:59
To: modeleng@xxxxxxxxxxxxx
Subject: [modeleng] Re: coarse threads

Hi All,
As well as the BSP and NPT threads why is it that all the UNC and
Whitworth threads are all the same pitch except the half inch,whit is 12
TPI and UNC is 13 TPI the form changes from 55 Dregees to 60 Degrees but
if you need to clean up an old thread either whit or UNC taps and die
would do to get things started.

yours John Burridge

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