My Take On
Using
the Metric System
Most of the tools we use every
day were designed for a world
market. Most everywhere but
in the US the metric system is
employed for weights and
measures. So, it is no surprise
that many tool manufacturers
design their tools around the
metric system and then
convert them to show inch
scales for the US market.
While few of us in the USA
grew up with the metric
system, and certainly do not
think in metric length terms,
learning to measure using the
metric system is far easier than
using the base 8 “inch” system
for building furniture. There,
everything is a fraction of an
even multiple of 8; one eighth,
one sixteenth, one thirty
second, etc. While we have
learned to add and subtract
odd fractions over the years,
the process is still very time
consuming and error prone.
On the other hand, measuring
using the base 10 metric
system is very straight
forward. You never deal with
fractions, only whole numbers.
The process is much faster and
far less error prone. As an
example, lets say you want to
build a rail, stile and panel
door for a project. You want
the door to be 19 3/8” wide.
The rail and stile pieces are 2
5/8” wide by ¾” thick and all
the groves are 3/8” deep. You
want to know how long to cut
the top rail piece. Lets see, it
will be 19 3/8” less 5 1/4” (the
width of the two stiles on
either side) plus ¾” for the
tenons on each end. Think
you can do that one in your
head every time without error?
Now try the same thing using
the metric system. The door is
500mm wide. Rails and stile
pieces are 50mm wide by
20mm thick with 10mm
groves. Now the calculation is
500 less 100 plus 20. Easy to
do that one in your head
without making a mistake,
isn’t it?
From my experience the best
thing you can do to improve
the accuracy, quality and
speed of building your
woodworking projects is to
spend the couple of weeks it
takes to convert to using the
metric system for your
measurements. You don’t
need to learn to think or
visualize in the metric system,
just use it for your
measurements.
The easiest way is to buy an
inexpensive tape from a big
box store that shows both, like
the one in the picture.
Do your thinking in the inch
system and measure using the
metric system. A couple of
weeks later you will find
yourself thinking in the metric
system more and more, and
liking it far better.
I splurged and also bought a
couple of rigid steel metric
rules with a matt finish that I
really like. They are easy to
read in any light and “dead
on” accurate. One is 150mm
long (about 6”) that lives in my
apron pocket. It’s great for all
those shorter measurements
like setting the fence to blade
distance on my large band saw
where you can put the end up
against the fence and read in
mm the exact dimension to the
inside tooth on the carbide
blade. The other rule is
500mm long (around 18”) that
is always nearby on the layout
bench.
A cheap metric/inch digital
caliper rounds out the
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