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His notes have just been found after 610 years. I have a similar
filing system. This was 545 years before the National Health
Service, so Bradmore was paid two pounds a year for life for this
stunning op. (Interestingly, US Republicans berate the cost of
the UK NHS as it devours 9.0% of GDP. How much does the US
spend on public heath care? 16.6% of GDP. But with their costs,
you don’t get much for your money.)
I had looked for answers on making early screw threads in a
slim, modestly titled book ‘One Good Turn’ which unfortunately
goes straight from ancient history to the invention of screw cutting
lathes in the 1750s. The author has the very New York name of
Witold Rybcznski and will be familiar to many of us. I am sure
he is on my opticians Snellen chart too.
The principle of the screw was known to the ancients.
Archimedes was not able to take out a patent on the Archimedes
screw as it was in use well before he was born in 287 BC. It was
reckoned to have provided the sprinkler system for the hanging
gardens of Babylon as well as early bilge pumps. You would
need boat builder’s skills to make one of these as it relied on a
waterproof spiral in a tube. They
are very efficient and still used in
Dutch drainage systems.
Timber screws were hand-
carved for wine and linen presses
since Roman times. They cut the
female block in half to chisel the
threads then fastened the halves
together, probably using trunnels
(tree nails) with wedged ends. Try
that in a TAFE woodwork class.
Gunsmiths and clock makers
made their own fine threaded
screws and coarser general
purpose ones were available,
mainly for fixing locks and the
newly invented butt hinge to
doors. Blacksmiths produced forged steel screw blanks which
were distributed to a domestic cottage industry where families
cut a slot in the head with a hacksaw. Then the thread was filed
by hand, often using a crude foot-powered spindle.
In 1760, two Midland brothers patented a screw making
machine where an automatic cutter could churn one out every
seven seconds. In 1740 Britain produced less than a hundred gross
screws. In Nelson’s day, this was seven million gross.
Yet very few screws found their way into the shipyards.
There were more screws in the officer’s watches and navigation
instruments than in the structure of HMS Victory. Boatbuilders
preferred the security, cheapness and strength of clenched
fastenings and trunnels, but these were more labour intensive.
Only after the automotive industry used powered screw
drivers and square slotted screws did US boatbuilders use screw
fastenings for mass produced light craft hulls.
The industrial revolution was fired by visionaries, often from
humble backgrounds who dreamed up new machines then had
to devise and make new tools to manufacture them.
Take the Yorkshire apprentice cloth maker Jesse Ramsden,
who turned to making precision instruments. He spent 11 years
building the first all metal lathe to cut screw threads ... and using
the first diamond tipped tools. His threads were accurate to one
four–thousandth of an inch. In 1770, Ramsden made a sextant
for another Yorkshireman, Captain James Cook.
How about the hefty blacksmith Henry Maudslay, son of a
Kent wheelwright whose massive hands made a precision lathe
to cut fifty threads an inch in a 5ft 2ins rod. He built his own
micrometer with a screw that could measure one ten thousandth
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