# Adding ground to Atlas motor?



## Birdpath (Jul 5, 2020)

Hi: Just pulled the old wiring out of my Atlas 7B shaper and running a new power cord. Is it worth adding a ground to the motor? If so, what is best practice? I found a copper ground lug and also have some star washers to use with a post and ring terminal? Would I just drill a hole in wire box? Thanks for any input. Daniel


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## talvare (Jul 5, 2020)

It's not a bad idea to add the ground wire. Adds a little safety factor and yes, connecting it as you've indicated will work just fine.

Ted


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## HarryJM (Jul 5, 2020)

I always add a ground wire for my motors as it is a safety factor.


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## JPMacG (Jul 5, 2020)

Yes, I added ground.  I'm a grounding fanatic.  I used to work on "AC/DC" radios with hot chassis.  I learned to hate getting the 120 V jolt.  The green wire in the photo is the ground wire from the power cord.  It terminates in a spade lug that is clamped under the lower right motor housing screw.


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## wa5cab (Jul 6, 2020)

Right.  Never use a 2-wire cord on a motor.  Always install a cord with a green ground wire (if the only cord coming to the motor is from a reversing switch and the line cord goes to the switch instead of the motor, then the cord to the motor needs 5 wires, not 3).


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## dwentz (Jul 6, 2020)

Yes do it.
I have (had) two pieces of old equipment in the shop that did not have grounds. A bench grinder and an old Craftsman drill press that belonged to my step father. A recent rearrangement in the shop put them close together, and as a result I got bit.  I was using a wire wheel on the grinder on a long rod to clean up some threads on the end. I took a good shock to the arm that was resting on the drill press table to steady the rod. Needless to say the drill press is now grounded and the bench grinder has the plug cut off until I can take it apart to rewire it.


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## markba633csi (Jul 6, 2020)

Find a screw that goes directly to the motor frame. If the motor box is screwed to the motor, then put your lug under one of those screws, with lockwashers.  You can also use one of the 4 motor case bolts to attach to.  Using the box cover screws is possible but the least desirable- it can vibrate loose. 
-Mark


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## wa5cab (Jul 6, 2020)

And after you get everything hooked up but before you button it up and plug the AC line cord into the AC socket, do the following. 

Using an analog ohmmeter or multimeter (not a digital one), set it to the lowest Ohms range (probably R X 1) and Zero it.  Connect it to the two flat blades of the line plug (US 120 VAC standard) or to the two Hot pins or blades (all 220 to 240 volt systems).  There should be no reading with the switch OFF.

Turn the motor switch ON (with a FWD-OFF-REV switch make the test twice, for both directions).   The meter should indicate a few ohms.  It should not read Zero other than possibly momentarily.  If it does, either you have made a wiring error or something is shorted to Case .  Either fix the error, fix the motor, or scrap the motor. 

Change to the highest Ohms range (probably R X 10K) and zero the meter.  Connect the meter leads to the ground pin and either or both of the other two pins or blades of the line plug.  With the switch off, the meter should read Infinity.  Turn on the motor switch or turn it to FWD and then REV.  The meter should continue to read Infinity.  If not, fix the wiring, fix the motor or scrap the motor.


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## silence dogood (Jul 6, 2020)

Let's go one step further.  You most likely have a two prong AC plug.  I'd change the cord to a three prong plug with a color coded wire.  Green is your ground and that goes to the motor case and the round prong.  Black is the hot and it goes to the on/off switch and then to the motor and the small prong.  White is the neutral  goes to motor and the wide prong on the plug.  I'll add that some cords already have a plug. Still, follow the color code.


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## Birdpath (Jul 6, 2020)

Thanks to everyone for their very helpful and specific replies. I will put all of this into effect and move ahead with getting this new addition to the shop situated. Best to you all. Daniel


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## turnitupper (Jul 7, 2020)

wa5cab said:


> Using an analog ohmmeter or multimeter  (not a digital one)


Why not digital?. I have some good digital meters including a four wire low ohms meter that i use for testing motors. Is this wrong?


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## wa5cab (Jul 7, 2020)

If you know what you are doing and know what readings to ignore, you can use a digital ohmmeter.  But explaining what you may need to ignore is just too time consuming.  So it is much quicker to just say use an analog ohmmeter.  Even a cheap one is going to give the true answers.  Not necessarily true with cheap digital ones.


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