Bench Grinder no longer spins just hums

[maximillian arango]

I have an old Delta bench grinder that no longer spins when started. I can get it up to spin by hand and then the motor takes over. I believe its the starter capacitor but I keep seeing people talk about the, "centrifugal switch," how do I test that? Or is there a way to test the cap, I hate wasting money so I would like to get it right the first time. The starter cap is marked 10uf 250v is there anyone able to direct me to one I'd greatly appreciate it, I found a few but I believe I will break the rules if I link them.

[Lee Schierer]

I found a few but I believe I will break the rules if I link them.

As long as you don't own the site, or work for the business, it isn't a wood working forum and it is relevant to the discussion links are allowed.

Generally speaking capacitors go bad far more often than the centrifugal switches. Almost any motor repair shop in your area should be able to check your cap and probably can sell you a new one.

[Bill Graham]

The switch bypasses the capacitor when the motor comes up to speed, the starter cap is what brings the motor up to speed so from your description it's toasted.

ereplacementparts.com will get you a suitable replacement. You can try your luck at grainger.com or eBay by searching for a cap with your specs but it's a toss-up whether or not it'll fit in your grinder. You pays your money and takes your choice,

[John McClanahan]

I would start with the capacitor.

[maximillian arango]

So I took it apart and I don't see (https://imgur.com/vxPAie6)centrifugal switch (https://imgur.com/vxPAie6), I guess its safe to say I don't have one!https://imgur.com/vxPAie6

For some reason the site wont let me host my images here

[Matt Day]

File size is probabaly too big.

[John K Jordan]

A local motor repair shop or an electrical supply house might have the right cap.

Also, when I was looking for one I ran into a guy from a local Maker's club who had 100s of caps and was willing to share. Might see if there is a club in your area.

JKJ

[Bill Dufour]

My old Stanley grinder has a cap but no centrifical switch.
Bill

[Bill George]

Grinders since they start without a load work just fine with just the run cap and the motor is called a PSC. When you have the cap out check for loose or broken connections and I am assuming you checked the motor bearings. So your Run cap is marked 10uf 250v and etc, and just go to eBay or I will use Amazon most of the time. If you take to a motor shop you will pay for labor and parts at full retail. They make their money on the commercial/ industrial users. Do not put a meter on those capacitor leads without discharging it first with a jumper wire. Run caps are silver or sometimes gray in color that is what you want, Start caps are black and are not intended to be in the circuit more than 30 seconds or so,

[Matt Berry]

Another option for a quality capacitor would be to check out either newark, digikey or mouser. Sometimes ebay isn't the best place to pickup quality electronic components.

[maximillian arango]

Run caps are silver or sometimes gray in color that is what you want, Start caps are black and are not intended to be in the circuit more than 30 seconds or so,


This is a big help I am guessing I ordered the wrong one so I canceled my amazon order, the one I ordered was silver and marked as a run cap the one I have is black and on the diagram it marked as a starter cap. I was reading that it shouldn't matter but I'd rather not roll the dice and burn the motor out. Can't seem to find one with the same uf and Volts AC so I'm going to order one with higher volts since it seems that is ok.

[maximillian arango]

My old Stanley grinder has a cap but no centrifical switch.
Bill

Seems to be true with mine as well, it was a pleasant surprise but I've got to be honest I was excited to mess with it so I was slightly disappointed I couldn't tinker.

[Bill Dufour]

Well my Stanley grinder bought at a flea market runs fine. I have never had to tinker with it. I did replace the cord since it was dry rotted. Still has what looks to be the original flat capacitor They quit making my model in 1938. It has a brass plate advertising "ball bearing".
Bill

[Bill Bukovec]

Have you tried spinning the wheels by hand, then turn the power on? If you have a sanding drum chucked in a hand held drill, you can spin the grinding wheels pretty fast.

[maximillian arango]

That is how I've been starting it but its getting old fast.

[Bill George]

This is a big help I am guessing I ordered the wrong one so I canceled my amazon order, the one I ordered was silver and marked as a run cap the one I have is black and on the diagram it marked as a starter cap. I was reading that it shouldn't matter but I'd rather not roll the dice and burn the motor out. Can't seem to find one with the same uf and Volts AC so I'm going to order one with higher volts since it seems that is ok.

If there is no switch then its a Run capacitor used as a Start. If its Chinese it could be any color!!! MFD is what counts, higher volts is ok as long as it fits. Post a picture of the old one.

[Steve H Graham]

It's normal for capacitors to crap out, so that's where you should look first. They are cheap and easily replaced.