Originally Posted by
WizardOfBoz
Good heavens! Starting with 43, a prime number? It won't work then...
Seriously, its an old machinist's trick, and you use "10" so that you don't mess up and forget to subtract the "1", if you start at 1. Starting at the 10 means that if you forget to use 46 and instead use 36, its more obvious. That's the theory, and folks have been using it for at least 100 years or so if I recall reading it in an old machinist's account. May not be too important here, agreed .
That's 2 prime numbers. It must be my Asperger's.
As a Marine Boilermaker (completed apprenticeship in 1971 at Puget Sound NS) we always used 1" or 1'. Or the hook if it wasn't that fussy.
They actually calibrated/repaired (some got beheaded under the shears etc.) our tape measures (tool room) so they were actually quite good.