that has been placed over their locations. This is not the
most accurate way to locate the holes, but this device
does not need a lot of accuracy so it’s just fine. Be sure to
take the interior features and location of the jacks into
account when doing this. Each hole location was punched
to make a dimple which helps to start the drill on center.
The holes were drilled on a drill press, starting with a
3/64” drill to make small pilot holes and then with the
final size drill (as shown in Photo 3) which follows those
pilot holes. When using this two drill procedure, the
location of the final hole will be accurate to a small
fraction of the size of the small pilot drill.
The plastic housing was held in a drill press vise to
prevent it from being grabbed by the drill and dangerously
spun around. The drill was fed downward slowly. A hand
drill could also be used with the cover held in a bench
vise. The 15/64” hole is just a few thousandths too small
for the stem of the switch, so a round file was used to
enlarge it just a bit. About a half dozen strokes were
enough to do this. A countersink was used to remove the
sharp edges of the holes both inside and outside, and to
bevel the edges of the cable holes (Photo 4).
A trick was used in mounting the switch. Most toggle
switches have a keyed washer that prevents the switch
from rotating in its hole. These keyed washers have an
internal key that fits in a key slot on the barrel of the
switch and a bent tab on the outside diameter that is
intended to fit in a small hole drilled near the main hole
for the switch. In spite of careful measurement and drilling,
this bent tab often does not fit properly, so a different
method was used in place of drilling.
The switch was placed in the hole in the case and the
keyed washer was placed on it on the outside, with the
tab resting against the plastic. Then, the nut was put on
just finger tight so it would not move around. A hot (600º
F) soldering iron with a small tip was placed on the
washer just above the bent tab, and light pressure was
applied until the tab melted in and the washer was flat on
the surface of the cover.
Be careful not to go too far; a gentle touch is best.
This worked perfectly and the appearance is very nice. It
looks a lot better than a drilled hole. I wish I had thought
of this trick about 30 years ago.
The wiring is done on the switch first, one row at a
time. The two sides of the switch are labeled “Fax” and
“B.P.” (bypass) to help. Keep in mind that most toggle
switches make contact from the common terminals in the
center row to the terminals on the side row that is
OPPOSITE to the direction that the switch is thrown. This
can be confirmed with an ohmmeter. The first row that is
wired is side #2 on the schematic, or the bypass side. Two
yellow jumpers on this row can be seen in Photo 5.
Next, four wires are soldered to the terminals of row
C on the switch, or the center/common row. It would
have been best to preserve the red/green color scheme,
30 December 2015
■ Photo 3. Layout of holes.
■ Photo 4. Drilled and cleaned holes.
■ Photo 5. The wiring.