Speaking as a yank who’s been trained in England, (London: The Cass)
the way I normally do things is to pick a system and run with it
until I need to change. Very rarely do I convert between them.
Because in addition to all the fun with various gages, (of which
there are several), number drills have been sadly neglected in this
tale of woe. At least over here in the States, most of our smaller
drills come in ‘number’ sizes. Zero through about 80, getting finer
as they go up. (about.120" to bloody fine. ?.005"?) I think the
numbers relate to Stubbs wire gage, but I could be wrong. They most
definitely don’t have anything to do with B&S, which is what we use
for precious metals. Just in case you think it’s that simple, there’s
also another gage system (ASW) that’s used for ferris metals. No,
of course B&S and ASW don’t match up. They’re offset by about 2
numbers, IIRC. But that’s not as much fun as the day I walked into
Blundels my first week in London to buy some sterling sheet. Planning
on doing some raising, I asked for a 6" square of 16 gage. It
arrived, slightly thicker than I thought it should have been, but not
too far off. Turns out the Brits use Birmingham gage for precious
metals, and that runs backwards of the American gages. (0 is very
thin, and 30 is very thick.) Luckily, the crossing point is right
around 16 gage.
Are we having fun yet??
In practice, what I do, and what I suspect most other folks do is to
work with gage for thickness of sheet, unless I need to do something
quantitative with it, at which point I pull out the digital
calipers, and figure out how thick it really is, in decimal inches.
(.0015" resolution.) Alternately, if it’s a rock or something, I’ll
work in decimal millimeters. All it takes is a push of the button on
the calipers to flip between the two systems. What I don’t do is
worry about doing anything with the other systems except calling for
something by name. If I need to match a wire, I mike it, and then go
fishing for a drillbit to match, as measured by the calipers,
regardless of what the ‘number’ says it should be.
I’ve given up on ounces for weighing things at school. Everything’s
in grams, and we don’t worry about troy, imperial or avoirdupois
ounces, or the variations thereof. Besides, you never have to ask “Is
that a liquid gram or a solid gram??”…
Sigh… Just give me decimal somethings. Fractions are tools of the