Metric threads

Hi,

It was a black day when Britain decided to change to metric threads - Ok, it
now means that we can go to almost any hardware store and buy 'stock' shiny
plated bolts in 'standard lengths' and 'standard heads' of either
countersunk or panhead but what is now getting very difficult is buying
bolts to replace those in existing old machinery or ones suitable for a
particular job.

Whoever decided on this 'standardisation' obviously had no idea at all of
what a thread is for! Each of the original thread forms - Whitworth, Brass
thread, Thury thread, B.A., M.E. UNF etc., was designed for a particular
purpose with carefully calculated thread angles and pitches to maximise the
strength of the joint. Now we are faced with only a very poor compromise and
a very limited choice. Of course, the old threads are still available from
'specialist' suppliers, but the price has risen to reflect their rarity ( I
wonder if I should start collecting 'old screw threads' to hand down to my
kids?).

Whatever it takes, I would say hang on to your existing screw system and do
whatever is necessary to educate your politicians and decision makers.

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk

----- Original Message -----
From: "Smoke" <Smoke@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: 03 December 2000 20:37
Subject: Re: [CAD_CAM_EDM_DRO] Re: Stepper cnc retrofit ? For Tape-O-Matic


> Metric threads have a greater clearance at the root diameter than US