TECHNICAL Measuring tools
32 The Woodworker & Good Woodworking August 2019 http://www.getwoodworking.com
marking lines made with the stock on the left
and then the right of the blade: if the two lines
run parallel, all is well.
Even more treasured is the 45° mitre square,
whose rakish charm challenges its owner to a
devilishly demanding test of precision. While it’s
good to mark around a board with the try square
and saw true to the continuous line, just for the
practice, it’s a more telling exercise to inject 45°
angles into the proceedings with the mitre square
(photo 1) and assemble a mitre joint. Whereas
some square-cut joints manage to conceal tiny
errors when assembled, the misalignment of a
mitre joint gapes like the beak of a yawning bird,
the daylight glaring through it, and the awfulness
unmercifully amplified if the wood happens to
be wide. My only chance of success (photo 2)
is to proceed very slowly from the first pencil
mark to the final push of the saw.
I suspect the mitre square is rarely used to
mark mitred corner joints now, since a machine
does the job without risk of human error, but for
me it’s unforgiving way provides an invaluable
reminder of the need to improve. When it comes
to testing the veracity of the mitre square itself,
repeating the exercise of the try square should
yield two lines perpendicular to each other;
a blade more than one degree out is not worth
the frustration, and best treated as an objet
d’art for the mantelpiece.
For all other angles a protractor is a useful
tool, and the most versatile is the one that’s part
of an engineer’s combination set, able to be locked
at any angle and point along its steel rule. Besides
marking out (photo 4) it’ll reveal the true bedding
angle of a plane, and is good for setting up a
sliding bevel as a visual guide to honing chisels
(photo 5). Meanwhile, the machined faces of the
square head that comes with the combination set
make it free-standing, unlike many try squares,
so I use it as a guide to the vertical when using a
hand drill (photo 6). Add to that the built-in spirit
level and scribe and this tool should be irresistible,
yet its cold, hard-edged skeleton of steel bristling
with tiny scales seems alien in the warm-handled
company of woodworking tools.Tools without numbers
Back to those satisfying tools unencumbered
by numbers, and two stalwart examples infallible
in their workings – the level (photo 7) and the
plumb bob (photo 8). The level demonstrateswhat’s horizontal and what isn’t by virtue of its
buoyant bubble in a curved vial, while the plumb
bob, typically a shapely inverted onion dome of
steel-tipped brass, hangs indisputably vertical
under the influence of gravity. And how irritating
these two can be when the shelf’s up and the post
fixed, having the cheek to offer a critical last word
on a job which had seemed to be going so well.
The marking gauge not only scribes parallel
to the edge or face of a board (photo 9) but can
accurately bisect it by adjusting the stock to
marks made through trial and error from opposite
sides. Simpler than that, a line pencilled under
the guidance of the fingers, acting as a fence,
is often good enough (photo 10).
Just as the marking gauge measures and
marks in one, so also does the chisel, and it’s an
under-exploited feature of the graduated set that
they’re effectively a set of gauges too, typically
stepping off in units of 6, 12, 18 or 25mm. With
the one chisel you can step out the dimensions
of a small dado, for example, scribe and hammer
down on the marks, then begin to excavate the
waste (photo 11).
Having the chisel define the width of the
opening is the normal way when cutting a9 Scribing with the marking gauge
12 Setting the mortise gauge to the chisel
10 Marking a parallel guided by the ‘fingers fence’
13 The chisel defines the mortise width11 Dado cut to the width of the chisel14 A lock mortise chisel levels the floor