.225 dia x 40 tpi die

.225 dia x 40 tpi die

This topic has 25 replies, 14 voices, and was last updated 8 January 2017 at 09:32 by Michael Gilligan.

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8 January 2017 at 09:32 #276435
Michael Gilligan
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@michaelgilligan61133
If I might be forgiven for last night's stupidity … Here's an another hypothesis:

Perhaps Parker Hale chose to use [almost] the full 'fundamental triangle' of a Whitworth thread-form; so as to give longer flanks to a thread which needs a precision fit.

As illustrated here [borrowed from Wikipedia];

the Whitworth truncation of the fundamental triangle is H/6 which, for 40tpi I calculate to be roughly 4 thou.

[someone please check this figure]

That would make a 'fully extended' version of the 7/32 40tpi thread

0.21875 + 0.008 = 0.22675 inches, outside diameter.

… a tiny rounding of the crest then takes us down to 0.225"

_______

As I have never examined the thread-form on a Parker Hale component; this is mere speculation … but I think it would merit investigation.

MichaelG.

.

https://en.m.wikipedia.org/wiki/British_Standard_Whitworth

Edited By Michael Gilligan on 08/01/2017 09:33:41
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