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Only sightly off subject
Posted: Mon Jul 08, 2002 2:12 pm
by p.cole@ntlworld.com
Hi gang
More than a few years ago, when I was at school, I remember being force to recite Mr Whitworth s formula that he devised for relating the diameter of one of his bolts to the A/F dimension of its corresponding nut. I can t for the life of me remember the formula now, nor can I find it in Machinery s Handbook or anywhere on the web.
As best as I can remember it went something like:
A/F = (O.D. x 1.25 + 1/8) inches.
Thus the A/F dimension of a 5/16 bolt should be 0.3125 x 1.25 + 0.125, or 0.516 inches.
This formula seems to get into the right ballpark each time, but modern practice seems to vary. Does anyone know why? Surely just because poor old Mr Whitworth turned his back somebody didn t get in there and fool around with it did they?
Re: Only sightly off subject
Posted: Mon Jul 08, 2002 4:27 pm
by Dave & Diana Dwyer
When BSF threads were introduced, the finer thread meant that a given torque
on the spanner would produce a greater tension in the fastener.
To offset this, the spanner sizes were all stepped down by one: hence a
spanner-end would be marked 1/4W 5/16BSF. If you can find an #OLD# 1/4W
bolt or nut you will find that the AF is clearly bigger than on a 1/4BSF.
I think from about post-war the hex on Whitworth was reduced to the same
size as on BSF, and many years later the practice of dual marking was also
dropped.
Regards
Dave Dwyer
J2, TA, TC
Re: Only sightly off subject
Posted: Mon Jul 08, 2002 5:02 pm
by Badger
To whom:
A Whitwhorth bolt is not whorth a whit whithout a whitwhorth whrench whith
which to whrestle it.
Thank you
Badger
Re: Only sightly off subject
Posted: Tue Jul 09, 2002 6:24 am
by Clifford Lockrow
Badger... Your really need a wench to wrench a whitworth wrench!!!!
BADGER wrote:
> To whom:
> A Whitwhorth bolt is not whorth a whit whithout a whitwhorth whrench whith
> which to whrestle it.
> Thank you
> Badger
>
>
>
> Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
Re: Only sightly off subject
Posted: Tue Jul 09, 2002 11:47 am
by Roger Furneaux
Peter - there might well be a formula, but yours is not it! All BSW head A/F
sizes are 1/16" less than the old original BSW heads (at least, up to 3/4
BSF) so your formula would have to give 0.600" for 5/16 Whit. (O/D x 1.52) +
0.125 gives the right result, and is nearly correct for other sizes, but
not all.
I think the old larger Whit sizes were discontinued during the WW II to save
steel, but spanners (and wrenches!) used the dual size markings for many
years after.
Hexagonally
TCRoger
Peter Cole wrote:
>More than a few years ago, when I was at school, I remember being force to
>recite Mr Whitworth s formula that he devised for relating the diameter of
>one of his bolts to the A/F dimension of its corresponding nut. I can t
>for the life of me remember the formula now, nor can I find it in
>Machinery s Handbook or anywhere on the web.
>
>As best as I can remember it went something like:
>A/F = (O.D. x 1.25 + 1/8) inches.
>
>Thus the A/F dimension of a 5/16 bolt should be 0.3125 x 1.25 + 0.125, or
>0.516 inches.
>
>This formula seems to get into the right ballpark each time, but modern
>practice seems to vary. Does anyone know why? Surely just because poor
>old Mr Whitworth turned his back somebody didn t get in there and fool
>around with it did they?
>
>
>
>
>
>
>Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
>
>
[Non-text portions of this message have been removed]
Re: Only sightly off subject
Posted: Wed Jul 10, 2002 10:39 pm
by Sam Suklis
Ahhh....Badger: Whitworths interchange with SAE wrenches in 32nds and
64ths.
Best regards from the rainforest,
Sam.
----- Original Message -----
From: "BADGER" mrbadger@cox.net>
To: "MG-TABC" mg-tabc@yahoogroups.com>
Sent: Monday, July 08, 2002 4:11 PM
Subject: Re: [mg-tabc] Only sightly off subject
> To whom:
> A Whitwhorth bolt is not whorth a whit whithout a whitwhorth whrench whith
> which to whrestle it.
> Thank you
> Badger
>
>
>
>
> Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
>
>
>