Diagonal squaring aids
Cabinetmakers can measure diagonal dimensions
without the aforementioned constraints of a tape, using
a direct reference method. In most cases, I turn to the
oldest, basic tool to make sure the work is not out of
square: pinch rods, or bar gauges. They use the same
diagonal principle as the tape measure: set the tool to
one diagonal, then use it to check the other. If there is
no difference, bingo – the work is square!
Some woodworkers cut a pair of sticks and assemble
them with commercial bar gauges – but why not make
your own pinch rods using components that are widely
available? Let me share four of those that I have built
for occasions when neither a square nor a tape would
do the job.
Binder-clip pinch rods
As the name suggests, pinch rods are two rods pinched
together. The simplest way to keep two strips together
is to use a binder clip. A clip gives enough pressure for
the holding while, unlike spring clamps, still allowing
you to extend either strip with your thumb (photo
3 ). Avoid using this method with very long strips as a
pair of clips would be needed, which would make fine
adjustments too cumbersome.
Ball-valve pinch rods
At an antique store, I once saw some homemade pinch
rods clamped together by a copper valve. I found another
type of ball valve at my local home centre, and the only
small challenge I faced was finding a wooden rod and
cutting it into halves to fit into the valve (photo 4).
You will find the bandsaw a safe way to rip the rod,
followed by some hand planing work (photos 5, 6).
In the last step, bevel the ends to about 40° (photo 7).
To use, slide the strips apart until the ends contact the
opposite diagonal corners, then lock them down with
the thumbscrew.
Shaft-clamp pinch rods
I came across a neat idea of using a dual marking
gauge’s shaft clamp (designed to lock the relative
position of the cutters) to pinch two dowel rods
together (photo 8). The clamp holds the rods in
position as the thumbscrew is turned.
First, find a pair of wooden rods of the right diameter
(3/8" for the extruded aluminum shaft clamp, for
instance), and cut them to desired lengths. To complete
the tool, sharpen the ends with a pencil sharpener, and
slide them into the clamp holes (photo 9).
Diagonal beams
Both Charles Hayward and Ernest Joyce have covered
in their books the diagonal strip with a pointy end as a
http://www.woodreview.com.au 81PROJECT10
11
12
- The chisel-edge block is set back from
the end of the strip so it can rest on
the assembly. - Ripping a batch of beams before
crosscutting them to various lengths,
including a shorter piece for making
the chisel-edge blocks. - Cut one end of the strip to
a point like a chisel edge,
at an angle between
45° and 60°.