Informative post. THANKS!
TtT
--- On Thu, 10/15/09, Carmods@aol.com <Carmods@aol.com> wrote:
> From: Carmods@aol.com <Carmods@aol.com>
> Subject: [Tigers] Whitworth Threads
> To: tigers@autox.team.net
> Date: Thursday, October 15, 2009, 10:05 AM
> Here is some brief information
> you all have wanted to know about
> Whitworth threads. You will be amazed at how
> interesting a topic this will be at
> your next party. If you need more detail let me know.
>
> It is considered by some that the screw thread was
> invented in about 400
> BC by Archytas of Tarentum (428 BC - 350 BC).
> Archytas is sometimes called
> the founder of mechanics and was a contemporary of
> Plato.
> Early screw threads for fasteners were cut by hand,
> hindering mass
> production Through the years, increasing demands
> deemed it necessary for them to
> be factory made. In 1770, Jesse Ramsden made
> the first satisfactory
> screw-cutting lathe. J and W Wyatt patented a
> factory made thread system in 1760
> but the lack of thread standardization made fastener
> interchangeability
> impossible.
> To overcome these problems Joseph Whitworth collected
> sample screws from a
> large number of British workshops and in 1841
> proposed standardization of
> the number of threads per inch for various diameters
> and the angle the
> thread flanks at 55 degrees . His proposals became
> standard practice in
> Britain in the 1860's.
> Course Whitworth threads called BSW (British Standard
> Whitworth) from 1/4"
> to 1" are the same threads per inch as UNC (Unified
> Course) except for the
> 1/2" which is 12 threads per inch for BSW and 13
> threads per inch for UNC.
> The major difference is that the UNC has 60 degrees
> between the thread
> flanks and a deeper minor diameter. The
> BSF (British Standard Fine) thread
> has the same profile as the BSW thread form but was
> used when a finer pitch
> was required for a given diameter.
> Except for the 1/2" thread BSW, threads can be
> modified with a tap or
> chased with a die to fit a UNC nuts and bolts.
> Due to varying sizes of taps
> and dies, try it first to make sure you are satisfied
> with the fit. The
> threads per inch of BSF (British Std. Fine)
> have no correlation to UNF
> (Unified Fine) so they cannot be re-tapped or chased with
> a die.
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