TECHNICAL Small-scale CNC
72 The Woodworker & Good Woodworking October 2019 http://www.getwoodworking.com
end-grain on plywood is left quite ragged (photo
8 ) and requires some cleanup, particularly if
applying a finish that might raise the grain further,
such as water-based dye. I haven’t yet cut gears
in Perspex but am considering building a clock
entirely from different colours and thicknesses.
The problem with solid wood is stability and
even small gears have a habit of turning from
round to oval. I have made up blanks for large
gears from 30° segments, which I then ran
through a thickness sander to ensure flatness
but after cutting the gear some twist still
developed. Fine-grained woods such as beech
work well but oak and ash are fine for ‘chunkier’
components – trying to cut a delicate gear in oak
can lead to fractures along the grain (photo 9).
Photo 10 shows some of the components
for a weight/pendulum driven clock and photo 11
shows the clock during assembly. The numbered
‘face’ is in recycled oak (from the benches in
the local magistrates court when it was being
converted into offices and flats) and the gears
are made from some recycled mahogany (from
old park benches). The frame was from a recycled
shelf of unknown wood variety.Cutting letters & shapes
This is another area that CNC excels in and it
opens up a new world of possibilities from making
signs to putting personalised messages onto your
work: clocks, boxes, and other items, which have
personal messages, make great gifts and many of
my relatives have at least one item I have made.
Photos 12 & 13 show an example clock using
a battery powered insert. The lettering has been
filled with a mix of acrylic resin and powdered
brass and, once hardened, sanded flush. As the
fingers are exposed and easily damaged, this type
of construction lends itself to wall mounting and
I provide a wooden case to transport them safely.
The clock in photos 14 & 15 had the lettering
filled with polyester resin, which can be coloured
with dyes. Resin kits, including a set of coloured
dyes, can be bought online. One thing to note
about polyester resin is that until it sets it stinks
like nothing else on earth, so working outside
is therefore highly recommended. This particular
clock was for a friend’s retirement – as teenagers
we used to terrorise the neighbourhood on our
Lambretta scooters. He bought one again andis a member of a scooter club, hence the relevance
of the clock.
My version of Gilly the Giraffe appeared in
April’s edition of The Woodworker and photo 16
shows one of the details I added to personalise it.
The clock and plaque in photo 17 I made for
my granddaughter’s bedroom when she was born.
In this case the mechanism is an enclosed radio
controlled clock. A closer look (photo 18) reveals
a couple of small holes in the brass resin infill;
this is caused by bubbles of air, which rise to the
surface before the resin sets. Applying gentle
heat from a gas torch or hot air gun can help
eliminate these – more heat required next time!
Another project for my granddaughter was an
art easel (photo 19) – on one side is a blackboard
surrounded by the alphabet. Rather than use
blackboard paint I used self-adhesive vinyl
blackboard material, which comes on a roll, similar
to Fablon. Instead of inlaying the letters with
resin, I painted inside them with coloured enamel
paints. Unfortunately the paint soaked into the
wood grain, which led to the colours bleeding
beyond the letters; this was in spite of painting
the recesses with sanding sealer first. I was going
to use clear varnish on the frame but instead
carefully roller painted it grey. The other side of
the easel (not shown) is a magnetic whiteboard
with numbers 0-9 and shapes around the frame.
Also for my granddaughter was a toy box on
wheels (photo 20). Inside and out is personalised
with the alphabet, her name, a big gold star, and13 Rear cut-outs for clock 14 Coloured polyester resin inlay9 Oak is not suitable for very slim gears
12 Epoxy and brass powder inlay
11 Clock assembly
10 Mahogany components for a clock