On 2007-06-02 00:14:10 +0100, Frank Erskine
said:

On Fri, 1 Jun 2007 21:28:38 +0100, Andy Hall
wrote:
Most of mine are 12,7mm with a few 6,35mm.

Is there any real significance in this '12·7mm' and '6·35mm' stuff?

Why not ½ or ¼ inch, which it really is?


Because I work in metric.

All of my fixed machinery has metric scales only.

I have some measuring instruments such as an Aigner Distometer, which
is used to help set up machines, which also has metric reading only.

http://www.vos.nu/default.asp?catego... ht&type=nieuw


If

I'm using this to set up a router cutter in the spindle moulder, I am
certainly going to be thinking about 12.7mm bits (or whatever size the
bit is). Mix the systems of units together and there is sooner or
later going to be an expensive mistake.

There are one or two that I have like a Vogel electronic caliper which
has buttons to select between metric and deprecated imperial units. The
button has to be pressed for a while to switch. The display is
reasonably smart in that if it is set to imperial, it will show 0.75
inches as 3/4 in. Thus it's possible to see that it is set to the
wrong system of measurement. I used to have a cheap caliper,
since thrown away, which had decimal inches on the display when set to
inches. Under those circumstances with small amounts of distance,
it's possible to make mistakes. For example, 0.3 inches and 3mm if the
display isn't very good.

Gradually I've been throwing out tape measures, and rules etc.with dual
inch/mm markings. These things are useless because the wanted
measurement system is always on the opposite side to the side wanted.