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How-to Add a Switch and Grounded Wire to Old Motor (Update Your Shop Tools)!

Friday, January 27, 2017
Perhaps the biggest difference (and most important) part about re-storing my old drill press was updating all the wiring.

I've read horror stories about these old, all-metal machines carrying voltage through them and going straight to the person using it (because the machine wasn't grounded).  I certainly don't want to die so it was a huge priority to make this drill press safe before I could use it!

Also, I don't like the idea of plugging a tool in to turn it on so I wanted to add a switch.  I wasn't able to find any information on how to add a switch/grounded wire to a shop tool so I read a lot of electrical sites, forums and most importantly - I talked to my dad.  I wanted this thing to be "code" and for it to be done RIGHT so I can show people how to do it themselves.  (See disclaimer below)

This is the state I bought it in.  It looks like someone tried to add their own switch by roughing in an old lamp cord and wrapping the ends with a wad of electrical tape.  People, people.

The idea is simple, really.  To add a switch you need to have the hot wire 'interrupted' and that is done by having the hot wire connected to the switch on both ends - when it's flipped on/off the hot wire is "connected"/"disconnected".  


There's a small piece of wire section running from the motor to the switch box, and then the main (plug) wire running from the switch box to the wall.  The green wire is the ground wire and give an outlet for electricity to go rather than your body.  The ground wire is connected to the motor, to the switch itself and the metal box.

The switch box is attached onto a metal bracket I fabricated that is pressed between the motor and the bracket from the machine.


Before buying anything I looked up to make sure what gauge wire I needed according to how many amps my motor pulls.  It pulls 6 amps and 14 gauge wire was sufficient.  Do research for your motor.

These are all the supplies I used!  I estimate that everything cost about $25.

--I'll break it down--

WIRES:
1-foot 14-3 rubber cord (cut by-the-foot)
1-foot 14 gauge stranded green wire (cut by-the-foot)

BOX & SWITCH:
 1-1/2" deep electrical box
bracket*
2 snap-tite connectors
ground "screw" with nut that fits + other small bolt/nut**

*I modified a nail stop bracket to fit my needs exactly.  I used my grinder to cut off one end, bent it and drilled a new hole to fit my small bolts.

TERMINALS & WIRE NUTS:
terminals for 14 gauge wire/#10 stud size
medium-sized wire nut for neutral wires

I should first mention that my motor may be a little unusual from the fact that it doesn't matter what terminals I attached the hot and neutral wires (biggest clue was that the original plug could go either way into an outlet).  Yours may be different so do your research on it.

The first thing I did was prepare the metal box and bracket so it would fit just how I wanted on my machine.  They're attached with the 2 small bolts.

 I cut about 3" of the coating from my small section of wire that would go from my motor to the switch box.  I determined this size by figuring out how long I would my green wire so it could run from the terminal cover plate to a bolt on the motor.

 I slid the wires through my cover plate...

 ...and did an underwriters knot with the hot and neutral wires to shorten them but also add bulk so they couldn't pull out.  I trimmed the hot/neutral slightly smaller because there wasn't a lot of room in the terminal housing for long wires.  Strip the ends of all 3 wires about 1/4".

 Add 1/2" pieces of heat shrink to each wire before tightly crimping terminals on the ends.

 Shrink tubing over terminal/wire ends with a lighter.

 Attach neutral/hot wires to studs (mine go between 2 brass washers and then the last bolt locks them in place).  Remember it doesn't matter what wire goes to which stud on MY motor - but yours could be different!

 Ensure the wires/terminal ends won't be under stress or bend funny inside and close cover plate.

Attach ground wire to motor.

 Cut a 6" piece of your green ground wire and add a terminal+heat shrink to the end and screw onto the ground screw of your box...

...and while you're at it do the same with a 4" piece of ground wire and attach to ground screw on switch.

 Punch out the metal circles of your box where you want your wires to enter/exit and push in your snap-tite connectors.

 Thread your wires through your connectors.  It made sense to have the plug wire coming directly from the bottom of the box and the cord from the motor coming in from the back.  Wait to tighten the screws.

 This is what my box looks like.  Kind of crazy but manageable-right!?  I cut my motor wire so I had about 4" of each wire hanging out (kind of long but better to cut more off later than too much now).

At this point if your wires are in position and the length you want them you can tighten the screws on your connectors - this pinches the cords so they don't pull out or have stress.

Strip about 1" of the coating from your neutral wires and twist the strands together clock-wise and tighten your plain wire nut over these wires until you can tell it's on well.  Push these wires back and out of the way.

Next I prepared my hot wires for my switch by adding terminals and heat shrink.  I have my ground wires with 1" of the ends exposed.

 Attach black wires to the screws on the side of your switch...

...and feed the ground from your box through the top hole of your wire nut and then the 3 others (with strands twisted clock-wise together) through the large end.  Twist wire nut clock-wise until everything is tight.  You can give your wires a slight pull to ensure they're secure.

Push your cords inside the box to allow the switch to be screwed in place.

Attach cover plate and wallah!  You've got yourself a safe-grounded machine that's easy to turn on & off!



*DISCLAIMER* please use safety, caution and common sense when working with electrical.  I will not be held responsible for any mishaps or injuries. Double check with an electrician to ensure the wiring for your motor and set-up is done correctly and to code.

If you want to see my post about re-storing this old Drill Press, click here.
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