Dayton 8” bench grinder sluggish start?

[strength_and_power]

Was given an 8” Dayton bench grinder that wasn’t working. Turning it on and giving a wheel a spin would get it going so it seemed like a bad starter cap. Replaced the cap with the same UF and the problem is still there.
Grinder is wired for 110 currently.
Thoughts?

 

[Codyboy]

I have a Jet drill press that I have to grab the chuck and spin it.
Replaced the caps and no change.
Pulled the motor apart and the start windings were fried.
A new motor is expensive. Even looked into having it rewound.
So I just turn it on, and give it a spin.

 

[dscheidt]

Does it have a centrifugal switch?

 

[strength_and_power]

Does it have a centrifugal switch?

Not 100% sure of what that is or where I’d find it. I do know it takes just short of forever to wind down after turning it off

 

[dave*99]

Not 100% sure of what that is or where I’d find it. I do know it takes just short of forever to wind down after turning it off

Centrifugal switch: It would be around the motor shaft inside one of the end caps.
Here is an example:

 

[Codyboy]

Not 100% sure of what that is or where I’d find it. I do know it takes just short of forever to wind down after turning it off

My Dayton 6 inch grinder looks exactly like yours except mine doesn't have a "safety type switch". Just a regular rocker.
And yes it takes forever to stop spinning when turned off.
I'm pretty sure mine has a centrifugal switch.
You can hear an audible "click" as the motor starts to slow down when powered off.

 

[Chuckster in NJ]

Centrifugal switch: It would be around the motor shaft inside one of the end caps.
Here is an example:

Sometimes the rivets break off and the switch fails. I had this problem on my Jacuzzi tub years ago so I took it apart and fixed the switch………. 15 years later it is still working.

BTW! I found this out AFTER replacing the capacitor. Now I have a spare "original working" spare.

 

[dscheidt]

Not 100% sure of what that is or where I’d find it. I do know it takes just short of forever to wind down after turning it off

the centrifugal switch disconnects the start capacitor after the motor is up to speed. After a start cap, they're the next most common reason motors won't start. They're usually easy to replace, and cheap.

Here's a pretty good video explaining how they work.

 

[strength_and_power]

Does it have a centrifugal switch?

Why yes it does. Looks like I’ll need a bearing puller to access it. I don’t see any markings on it. Time to consult the google lol

 

[dave*99]

You don’t need to remove it to perform some tests. Measure continuity across the contacts. Open and close the switch.
Isolate the start winding leads and measure the resistance.
Listen for it clicking when the motor spins up and and spins down.

 

[dscheidt]

Basically, your problem is the start winding isn’t working. The common problems are a bad start cap, the centrifugal switch, or the start winding is burnt out. A failed switch can cause a burnt start winding. But the tests are basic multi meter stuff. Lots of YouTube videos about how to teat a motor.

 

[strength_and_power]

You don’t need to remove it to perform some tests. Measure continuity across the contacts. Open and close the switch.
Isolate the start winding leads and measure the resistance.
Listen for it clicking when the motor spins up and and spins down.

I heard it click when it was winding down. I’ll put the meter to it when I’m at work tomorrow.
I’m guessing the start leads will come off the centrifugal switch plate?
A motor repair shop quoted me $450 for a rebuild, I won’t be going that route,

 

[strength_and_power]

Basically, your problem is the start winding isn’t working. The common problems are a bad start cap, the centrifugal switch, or the start winding is burnt out. A failed switch can cause a burnt start winding. But the tests are basic multi meter stuff. Lots of YouTube videos about how to teat a motor.

Looking at the starter cap I replaced, it almost looks new so maybe the previous owner tried that and then gave up.
Troubleshooting DC is something I’ve done a good bit of, not so much with AC, will search out some YT vids

 

[dave*99]

I heard it click when it was winding down. I’ll put the meter to it when I’m at work tomorrow.
I’m guessing the start leads will come off the centrifugal switch plate?
A motor repair shop quoted me $450 for a rebuild, I won’t be going that route,

Sort of. Can you follow this schematic? One start winding lead is on the switch . The other goes to incoming power, possibly through the power switch.

https://www.electrical4u.com/centrifugal-switch/

 

[fitter30]

Even with a sealed motor they will stick open then the cap isn't in the circuit. Spray it wd 40 the part with the spring.

 

[Davefr]

I'd check the start windings. What often happens is the start capacitor or centrifical switch goes bad and that leaves the start winding continuously energized. Start windings will burn up if left energized for more then a few minutes.

Do the start windings look discolored or smell burnt? How do they ohm out?

 

[strength_and_power]

I'd check the start windings. What often happens is the start capacitor or centrifical switch goes bad and that leaves the start winding continuously energized. Start windings will burn up if left energized for more then a few minutes.

Do the start windings look discolored or smell burnt? How do they ohm out?

Nothing smells burnt or off colored.
Doing some googling, I came across an article of a guy replacing the centrifugal switch on the same grinder. Looking at the pictures he posted against what I can see on mine, it looks like the thin metal plate the connects the blue wires is broken which effectively has the starter cap out of the circuit.

 

[RPH]

Looks like you found the root cause of the failure. Should be an easy fix.

 

[nadogail]

Basically, your problem is the start winding isn’t working. The common problems are a bad start cap, the centrifugal switch, or the start winding is burnt out. A failed switch can cause a burnt start winding. But the tests are basic multi meter stuff. Lots of YouTube videos about how to teat a motor.

Often those switches get filled with "dust", Compressed air can often clean them up enough to work.

 

[The Cobbler]

what I can see on mine, it looks like the thin metal plate the connects the blue wires is broken which effectively has the starter cap out of the circuit.

nice find .

 

[strength_and_power]

Often those switches get filled with "dust", Compressed air can often clean them up enough to work.

I don’t think compressed air will fix a broken piece but I’ll definitely use it prior to reassembly.
Years back, I had a smaller grinder from Northern tools and it was a POS that I rarely used it and ultimately ended up tossing it. Not sure how much use this will actually get once fixed. One side will definitely get a wire wheel which I can see getting a good bit of use. Probably mount this on a bench next to my 2x48 belt sander that definitely gets used.

 

[mm08822]

Until you open it up, you can't be certain.....

I had to fine sand the shaft on 1 motor so the centrif mechanism could move. It was the motor shaft that had surface rust.