B&D 6" bench grinder Type A. Every seen this?

Thread Starter

lonnie77

Joined Aug 17, 2017
2
I have a bench grinder that was turning slowly so I disassembled to check the bearings. What I found I have never seen before and was hope someone could tell me if I am missing a part. I looks as if once the motor starts to run centrifugal force overcomes the spring. I don't know if it is to disconnect or connect the brass rings.
 

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MaxHeadRoom

Joined Jul 18, 2013
19,004
Typically there is a centrifugal switch in a 1ph induction motor with a start capacitor, but that appears different from one I have ever seen.
Max.
 

shortbus

Joined Sep 30, 2009
6,973
Like Max, never seen one like that, but it is a centrifugal switch. The little button just rubs against the two copper rings on the end of the stator. Does the button move easily?
 

Thread Starter

lonnie77

Joined Aug 17, 2017
2
Thanks for the help. Yes it moves easily. There were two black traces of dirt on the copper rings that I cleaned off and I did not know if they were rub marks from one end of the plunger or just dirt left from the other end.
 

japj

Joined Sep 17, 2009
2
I have a bench grinder that was turning slowly so I disassembled to check the bearings. What I found I have never seen before and was hope someone could tell me if I am missing a part. I looks as if once the motor starts to run centrifugal force overcomes the spring. I don't know if it is to disconnect or connect the brass rings.
This looks like when I worked on rebuilding motors called similar to a shorting necklace in a repulse induction motor it is used to give more starting power as a starting capacitor would in a capacitor motor, once it reaches speed it opens the circuit to prevent overheating.
 

MaxHeadRoom

Joined Jul 18, 2013
19,004
This looks like when I worked on rebuilding motors called similar to a shorting necklace in a repulse induction motor it is used to give more starting power as a starting capacitor would in a capacitor motor, once it reaches speed it opens the circuit to prevent overheating.
Sounds like you are describing a shading ring as used in the small fan motors.
(as well as AC relays).
Max.
 

MrAl

Joined Jun 17, 2014
6,457
Hello,

There is a chance if not anything else, that you can replace the spring switch with a push button rated for the full voltage and current. This would be a "PUSH TO START" button. You push it and hold it for 2 or 3 seconds while the motor starts, then let go of it. If the motor spins up you've pushed it long enough, if it slows down again you did not push it long enough so push again and wait a little longer. Once the motor starts the button is released and it keeps running.
That's a possible fix if nothing better comes up and you cant replace the guts with new parts.
 
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