| In
This Article:
Two metal j-boxes are
attached to the underside of a wooden workbench, connected
with NM-B cable, and power is fed by a short 14 gauge
extension cord. |
Related
Articles:
- Building A Cheap (And
Sturdy) Work
Bench
- Index
Of Electrical Articles
- Links
To Other Electrical How-To Web Sites
|
| Skill Level:
2 (Basic) |
Time Taken:
1 Hour |
By
Bruce W. Maki,
Editor
 |
This work bench held a small table saw and a
belt sander. The bench sits near the middle of the garage. (A
table saw needs room in front and behind, so this bench needed
to be between the two garage stalls.) Power was provided by a
short extension cord, and it was becoming inconvenient to
continually unplug one machine to use the other. So, I decided
to hot wire the work bench. |
 |
I bought an 80 foot heavy-duty 14 gauge extension
cord, which is capable of handling 15 amps of electrical
current.
I cut the cord about 20 feet from the male end. (It goes
without saying that the cord MUST BE UNPLUGGED when making the
cut, right?) I've made dumber mistakes, I'll admit. |
 |
 |
The basic hardware required. Two smooth metal boxes,
some cable clamps, metal cover plates.
The first step was to install two cable clamps in one box.
(See How Cable Clamps Are
Installed.) |
 |
These metal junction boxes are "surface mount" boxes.
They are meant to be used with conduit and bolted to a wall. They
are commonly used in commercial and industrial wiring where the
conduit and boxes are just mounted to a cement block wall.
 |
I use hex-head sheet metal screws to mount things
whenever possible.
Two short screws installed with a cordless drill hold the
box securely and takes only a few seconds. Nails or screws can
be used. |
 |
 |
A 1/2 inch drill bit is used to drill a hole in
the lower shelf of the work bench.
The cut end of the extension cord is threaded through the
hole and into the electrical box.
|
 |
 |
The screws on the cable clamp are tightened. (Not too
much.)
These wire staples hold electrical cable in place, and they
cost less than a penny apiece. |
 |
 |
I start by running 14-2G cable into the
other receptacle box (the one that does not have the extension
cord feeding power into it) and fastening the cable to the
underside of the workbench. The cable is kept in the middle of
the 2x4 frame, so any nails driven into the bench will not
likely pierce the cable. I use plenty of wire staples. |
 |
 |
The wire staple is driven in just like a nail.
The cable is attached to the bench and then cut off so the
cable can enter the box and extend out four to six inches
beyond the box face. Better to make the cable a couple inches
too long than be too short. |
 |
 |
The cable is anchored firmly by the cable clamp.
The outer cable insulation jacket is carefully slit
with a sharp knife. Caution is needed because the three wires
inside are twisted and you cannot tell where they are, so it
is possible to knick the insulation. |
 |
 |
The insulation jacket is trimmed back.
Similarly, the outer jacket on the 14-2G NM-B cable is
slit. Two conductor NM-B cable (common household wiring) is
easier to slit because the cable is a ribbon and the bare
ground wire is in the middle. So, simply keeping the knife in
the middle of the cable is adequate. |
 |
 |
The cable jackets are removed. The green insulated wire is
a ground wire.
At the other box, the cable jacket is stripped and the
wires are stripped. |
 |
 |
The receptacle is connected to the wires. The bare ground
wire is looped under one of the mounting screws that holds the
box to the frame.
The receptacle is mounted on the box. |
 |
 |
Back at the other receptacle box... Three pigtails are cut.
The wires are stripped back about 1/2". |
 |
 |
The ground pigtail is looped under one of the mounting
screws, and then connected to the other two ground wires with
a green wire nut.
I always tug on each wire to ensure they are all snugly
bound in the wire nut. The flexible stranded wire in extension
cords sometimes does not hold well in wire nuts. |
 |
 |
The two white wires and the pigtail are held
together.
I wrap the stranded wire around the other two, solid
wires... |
 |
 |
...And then a yellow (small) wire nut is twisted on.
The wires often get twisted as a result.
The same thing is done for the black wires. Note the hooks
on the pigtails, for connecting to the screw terminals on the
outlet. |
 |
 |
The ground, white and black wires are connected to their
respective screw terminals.
And the cover plates are installed. |
 |
 |
One last thing. A staple is installed to secure the
extension cord to the frame of the work bench. Just in case
the cord gets kicked it won't put much stress on the cable
clamp.
The extension cord is plugged in and the outlets tested.
(Of course they worked perfectly.) At this time I realized
that the old extension cord had no ground prong... a safety
hazard when used to supply power to woodworking machines made
mostly of metal. At least that hazard is gone. |
Approximate Cost: See material list below.
|
Tools
Used:
- Cordless drill
- Nut-driver bit, 1/2 "
spade drill bit
- Hammer
- Sharp Knife
- Wire Cutters
- Wire Strippers
- Phillips and Flat-blade
Screwdrivers
|
Materials Used:
- Receptacle boxes - 2 @
$0.69
- Outlet Covers - 2 @ $0.39
- Cable Clamps - 3 @ $0.19
- 14-2G Cable - 6 feet,
approximately $0.35
- 80 foot heavy duty
extension cord, $14 (I used only the male end and 20 feet
of wire.)
- Total - $17.08
|
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