http://www.getwoodworking.com August 2019 The Woodworker & Good Woodworking 39
The original article, which was published in
the March 1953 issue of The Woodworker4 The three template pieces should fit together seamlessly 5 Secure the template to the edge of the maple
Making the key piece
I initially made a dummy run using some scrap
wood to get an idea of what was involved. For
the final project, I chose two hardwoods that
contrasted well in colour. The key was made using
Canadian maple, a very hard creamy white colour
that contrasted well with the American walnut
used for the base. The key is 76mm long and
the curve on the underside starts and finishes
at the ends of the key. As can be seen in photo
5 , the positioning of the template is important to
achieve this. For the sake of safety, use double-
sided tape to secure the maple to a piece of scrap
cut to the same width and length as the maple.
This will provide the extra support needed when
the router is used to profile the maple (photo 6).
Alternatively, this part could be made using a file
and abrasive paper wrapped round a suitable
former. Cut the maple to a length of 76mm
ensuring the cuts start and end at the curves.
The method I found to work well was to cut the
key a little over-length and then to sand the ends
smooth. A disc sander really helps here if the
fence is set to 90°. The length of the key should
be the same as the width of the walnut housing
with the ends of the curves sitting on the edge
of the wood. At this point it is worth clamping the
two matching templates in place on the walnut
to cut the recess for the first stage of the recess.
Both should be butted tightly together and the
recess cut to a depth of 6mm (photo 7). If all
goes well, the template for the key should be a
sliding fit into the recess (photo 8) and should
fit whichever way round it is fitted in. With the
template positioned in the walnut, use a sharp
pencil to score two lines on the underside of
the MDF where it overhangs. Now remove the
template and position it on top of the maple key.
It has to be positioned bang on the centreline and
the maple must lie on the two pencil lines just
drawn (photo 9). Draw a line around the MDF
onto the top of the maple key and draw a straight
line from the ends of the curves just drawn to
the bottom outside corners of the key (photo 10).
Although I have shown the lines drawn in pencil,
I actually used a marking knife to score them,
but pencil lines show better in the photos.
Opening the slot
As mentioned earlier, the secret to this puzzle is to
have a curve cut into the walnut that matches the
curve on the underside of the key. To begin, set a
marking gauge to 12.5mm – the thickness of the
maple key (photo 11) – and score a line on each