Fixing A Bench Grinder That Will Not Start

Fixing a SiP 6 inch heavy duty (1/2 horse power) that will not start. It hums but does not start.
Please note that these usually contain running capacitors rather than start ones so if you do need to replace the capacitor check and if in doubt get a run one.

[@flbyrne99]

Thanks Ben. My grinder wouldn’t start unless I gave it a mighty spin by hand. A replacement was going to cost over £90 so I did what you showed. Removed the base plate, saw the capacitor and removed it. Elsewhere on KZbin I found out what it did and how to test it. It was not ok. Found the spec on the broken one for a replacement, got one off eBay for a fiver, refitted it with new spade terminals as the originals were too small. Cleaned it up, reassembled it, switched on and Bingo! Starts first time every time. Thanks mate! Saved me £85 plus I learned what motor capacitors do (as against lighting capacitors) so I’m well pleased!

[@BensWorkshop]

I am pleased to have helped. Oddly I am currently working on another much bigger capacitor start motor, but this one has a dodgy centrifugal switch. (This bench grinder does not). One thing I would say is, it feels much better to have fixed something than to have replaced it. Did you capacitor look like it had blown up, otherwise how did you test it? Also if your capacitor is on all the time, you need a run capacitor not just a start one. Many thanks for watching, please like, share and if you like the channel subscribe!

[@madeddiesman-stylemonsterm6662]

Nice restoration. Dealing with a capacitor makes this a lot trickier. Thanks for sharing this!

[@BensWorkshop]

Many thanks, this one was easy. I now have the same problem with the motor on my milling machine. Suspect the capacitor but it is a much bigger motor. Many thanks for watching, please like, share and if you like the channel, subscribe!

[@user-hm6cx7mc5l]

Hello I came across this video while searching for information about a similar situation. My bench grinder's capacitor is missing and the connections were tampered with. There's four wires from the pinion,and I can't figure it out. No schematics also,wherever I look. Can you give me some info on how this one is wired,so I can hopefully start mine after getting a capacitor for it? Much appreciated,and I subscribed as well. Thank you for the instructions

[@BensWorkshop]

Many thanks for watching and subscribing! Generally it is easier to find, see and reply to comments if you start anew rather than reply to an old comment. Have you got a multimeter? One that can measure resistance? If so start by identifying which coil is which. One should have a higher resistance than the other.

[@user-hm6cx7mc5l]

I appreciate you taking the time to answer. I read somewhere in the comments about centrifugal switch,so it turns out the wiring was setup correctly,i was just looking for a "missing" capacitor,but turns out I misplaced the centrifugal switch while disassembling and there was no initial contact with the clutch plate. So,to anyone reading this,learn from my mistake and mark exactly where on the rotor axel it's fixed. Have a nice day,and I'm off to watch more of your interesting content :)

[@BensWorkshop]

Neither of my bench grinders have them, they both appear to have run capacitors but some induction motors are "split phase" which means that they don't have a capacitor. Is yours a Sealey like this one? Also, please start a new comment thread as it will be easier to find your comment to reply to.

[@tadnauseum]

outside in the summer sun with no shop and a flea market bench grinder that worked yesterday. This helped. 😊

[@BensWorkshop]

I am pleased it helped. Many thanks for watching! Please like, share and if you like the channel, subscribe!

[@alvarokerosene6257]

Thanks friend for showing the activities in your workshop. Excellent.

[@BensWorkshop]

Many thanks Alvaro.

[@jerryfogg5270]

Hi Ben, thanks so much for your help! Mine was the same as this! Saved me a lot of money! Thanks from your American Cousin!! Jerry!

[@BensWorkshop]

I am very pleased that my video helped! I really don't like throwing things away so like to keep things going. Many thanks for watching, please like, share and if you like the channel, subscribe!

[@Everythings_Adjustable]

Excellent result Mate, If the grinder has been sitting outside and got wet that might well give you a little tingle I would leave it in the airing cupboard for a week I would also re do the earth connection in the motor (I expect you have done this already ) 👍 😊

[@BensWorkshop]

Odd that you should mention water... When I got it started it spat out a lot of water from the side with the wheel... I may open it up to check.

[@Everythings_Adjustable]

@@BensWorkshop Even if it looks OK I would leave it somewhere warm for a while, Also do capacitors break down if they get wet? would it be leaking through it's casing? I don't know just guessing

[@BensWorkshop]

@@Everythings_Adjustable Capacitors do brake down but I think this one is fine as it is in a plastic case. I will dry out the internals though.

[@Everythings_Adjustable]

@@BensWorkshop I love this sort of video, very interesting stuff 👍

[@BensWorkshop]

@@Everythings_Adjustable Many thanks Sparky!

[@user-hm6cx7mc5l]

There was no information on my machine,just an old one I inherited from my grandpa and wanted to clean it up a bit. The only clue is the bearings are made in England,if that's helpful at all. Other than that,I'm not sure how this motor is called in english,but yes,this seems to be the principle behind it. There's a plate with a thin piece of metal on it,that helps engage the coil with full voltage and kickstart the motor. Then after the rotor starts spinning,this centrifugal switch releases the piece of metal and it's normal single phase. So basically,this switch is replacing the capacitor. If misplaced on the rotor,a bit further away so it won't push this piece of metal enough to make contact,the motor won't start. Sorry if the description is not very accurate,I'm not very good at this,and only found out how it operates today thanks to the comments here.

[@BensWorkshop]

If it is a centrifugal start motor the switch is connected when the rotor is not spinning, then as the motor spins, the centrifugal switch operates to turn off the starting coil. For a bit of detail, see this part of a series I did on an induction motor with such a system (and no capacitor) kzbin.info/www/bejne/ZnPVeImndpKKhas If the switch works, all you will need to do is identify which wires are one coil and which are the other. Connect them in parallel. Turn it on. Check which way the motor runs. If it runs the wrong way, reverse one coil and try again. See this motor video for more of an idea (This one is a capacitor start but same principle.) kzbin.info/www/bejne/q6vHloGNiql8Z5Y

[@BensWorkshop]

Also, soon I will be publishing another video with a different arrangement of centrifugal switch that caused a lazy start.

[@baldoh.6897]

Thank you for making this video...

[@BensWorkshop]

Many thanks. Hope it was helpful. Many thanks for watching the video, please like, share and if you like the channel, subscribe!

[@GrumpyTim]

A nice easy fix - saves tracking down a replacement capacitor - I didn't hear a centrifugal switch so I guess that one is a motor run rather than just a motor start cap - probably anyway. The tingling on the case is odd though - maybe test it with a megger meter if you've got one, see if the insulation is breaking down.

[@BensWorkshop]

Tracking down a capacitor of the right value would not be difficult. You are correct that it would be a run capacitor, I've never heard a centrifugal switch in a bench grinder and certainly not this one.

[@GrumpyTim]

@@BensWorkshop True, that would be a fairly run of the mill motor capacitor - I've had trouble sourcing heavy duty ones in the past, but that was a fair few years ago. Is that a dehumidifier on your bench? Is it damp in there? My shed was dripping with condensation and things had started to go mouldy in places - I've installed some forced ventilation to try to circulate the air a bit better.

[@BensWorkshop]

@@GrumpyTim I've seen some fairly heavy duty motor caps about... Yes that is a dehumidifier and I have done a review of it... I do get condensation on the steel roof but will look to insulate it one way or another.

[@GrumpyTim]

@@BensWorkshop I used some of the bitumen based corrugated roofing - it was really quick to install compared to my usual plywood and roofing felt, but it really does suffer from condensation - ah well, I'll know for next time!!!!

[@BensWorkshop]

@@GrumpyTim Mine is steel because the part of the original shed I took down that survived the best was steel. Once I put some insulation under it, it will be fine.

[@jujutsukaisen-360]

Can replace 2.5 to 3.5 uf capasitor, it is same volts

[@BensWorkshop]

If the question is can you replace a 2.5 uf capacitor with a higher value 3.5uf, generally yes. What you need to check is if they are running or starting capacitors. Starting capacitors are switched out of circuit after the motor has started spinng. You hear a click on start up and after you switch it off as it is slowing down. My other videos on lathe motors (and my mill motor) have such switches and you can hear them click. This model of grinder has no switch so needs a running capacitor. Many thanks for watching! Please like, share and if you like the channel, subscribe!

[@AD-lx3bt]

Thanks for the helpful video. I have a (old) bench grinder that has the same problem. I replaced the original capacitor with the replacement from a motor repair outfit. Connected the new capacitor but still the same problem. Any ideas? Runs fine, just have to manually start it.

[@BensWorkshop]

Have you checked the coil that the capacitor connects to? Also do you hear a click as it starts to spin up and another as it slows down to stop? If so, there could be a centrefugal switch that is failing and the contacts may need a clean. Many thanks for watching, please like, share and if you like the channel, subscribe!

[@nathanppierce]

Looks pretty good! Do you have an idea how I could fix my old Shopmate 2601TO? It gets bogged down when I start grinding something against the wheel. THANK YOU!

[@BensWorkshop]

I am not familiar with it. What power rating is it? How big are the wheels and what have you on it? (Type of stone?) Also, many thanks for watching, please like, share and if you like the channel, subscribe!

[@nathanppierce]

@@BensWorkshop Thanks for replying! It says 5 inch grinder. Model 2601TO. Shopmate. 115 V.A.C. 60 HZ. 3.2 AMPS. 3500 R.P.M. McGraw-Edison Company. Arbor size = 1/2”. Max. Lamp Wattage 10 Watts. The left wheel is approx. 4-1/8” diameter, 3/4” wide. The right wheel is approx. 4-7/8” diameter, 3/4” wide. The right wheel wobbles sideways approx. 1/16”. They’re both look like stone, I imagine they’re different grits, but they look the same to me.

[@BensWorkshop]

Is there a power rating in either HP (Horse Power) or Watts? (1HP = 750 Watts) The 3.2 Amps probably refers to starting surge current.

[@nathanppierce]

@@BensWorkshop looks like the sticker doesn’t say that. I can’t find any other markings

[@BensWorkshop]

I had a google and I can see the ID sticker which as you say, does not say much. However it looks a bit like a Black and Decker I have which has 1/3rd of a HP. As I can't see it running and how hard you are pushing it, but all grinders will bog down if pushed. Sorry that is not more helpful.

[@2hotscottpro]

I have a hummer like yours .I have to spin it fast to run.It’s a Craftsman 120 volt in USA.It doesn’t have a capacitor.It has a small winding that’s wired to the big one on axel.You mentioned that’s called split phase.That’s all I know.

[@BensWorkshop]

How many wires do you have coming out of the pedestal? I could also have a centrifugal switch which might be stuck open.

[@2hotscottpro]

I found out it has a start relay that’s not made anymore.Oh well it’s a cheap one has plastic housing I bought for a few bucks.Seen a bench grinder thread on the Garage Journal where they were talking about this one back in 2017.Boy they tried to find a replacement but didn’t.

[@BensWorkshop]

Did you find the relay? If not all you have to do is work out what it does then I expect you can put together an equivalent from other parts.

[@2hotscottpro]

No I haven’t ..Like I said a bunch of guys looked without luck.Thanks for your comments.

[@BensWorkshop]

In which case you just need to work out what the relay does and how to replicate that. I suspect it just turns the coil it is connected to on for a short time at start up.

[@grandadsworkshop5394]

Nice one ben

[@BensWorkshop]

Cheers. I've just finished editing the video of making the flange washers.

[@PachiOnline]

Great job!

[@BensWorkshop]

Many thanks, and thank you for watching! Please like, share and if you like the channel, subscribe!

[@richglaser4566]

Mine doesn’t have a starter coil like they. When I start it I bye turning it I here’s set of points click in

[@BensWorkshop]

Ah. That would be a split phase with a centrifugal swicth. Check the contacts and clean, also check there's continuity to the switch. The switch will be at one end or the other of the motor. I had a similar problem in this motor but it took me a while to find: kzbin.info/www/bejne/m5LCnJakhKajh6M Though this motor did have a capacitor, there was nothing wrong with it. Many thanks for watching, please like, share and if you like the channel, subscribe!

[@richglaser4566]

@@BensWorkshop I fount the problem was the centrifugal unit it was cracked and moved

[@BensWorkshop]

Were you able to fix it?

[@UKscrapper]

Nice fix might be a bit damp if you got it from scrapyard try drying it out

[@BensWorkshop]

Yes, in fact when I got t spinning first time it spat water out. Thanks for watching!

[@awandepercival4299]

How to fix a start dat dont want to retain the bench grinder only works when u hold the start?

[@BensWorkshop]

Your problem is not clear. If you mean that it will only start and run if you hold the switch on, then there is a problem with your switch. Many thanks for watching, please like, share and if you like the channel, subscribe!

[@send2gl]

How satisfying to get it working. How old is it? Surprised it had a cheap Chinese starter coil and strange still getting a tingle from the switch but dont think you inspected that.

[@BensWorkshop]

It is very satisfying, but I don't think the grinder is that old, certainly probably less than 20 years old. I suspect that some damp got in it to give it the tingle.

[@BensWorkshop]

Oh, and it is a capacitor... I kept getting it confused in the video.

[@hewhofightsforgodeveryman3942]

👍

[@samsgarage1716]

Nice job.Just a bad connection. I was thinking you was going to take out a starting capacitor from something else.How would you have fix it if the starting capacitor was messed up?

[@BensWorkshop]

In that size they are generally run capacitors and basically you just buy a replacement. They are sold as generic spares by value so as long as you can read what is on them or find out elsewhere you will be fine.

[@samsgarage1716]

@@BensWorkshop I learn something new every time I see your videos.

[@BensWorkshop]

@@samsgarage1716 Many thanks Sam!

[@kingbeejonga3720]

Nice one .I have the same machine.I"be been using it for over 15 years.I"m a shoe maker.now it won't on.no power at all.what can i do.keep up the good work thanks.

[@BensWorkshop]

Sorry to hear your machine has stopped working. Does your make any noise when you turn it on? Many thanks for watching, please like, share and if you like the channel, subscribe!

[@kingbeejonga3720]

@@BensWorkshop no .no power at all.it"s dead

[@BensWorkshop]

Have you got a multimeter? You could check it has power inside the unit. However you could also just try changing the fuse. It is a 1/2HP so will have a starting current of between 5 and 10 amps. Have you checked the fuse?

[@kingbeejonga3720]

@@BensWorkshop no.I didn't" know there"s a fuse.I will check.tkanks so mush for your kindness.

[@BensWorkshop]

@@kingbeejonga3720 No problem. Which country and type of plug is it? If it's a UK plug (used in UK, Ireland, Malta, many parts of the Middle East and Africa) then the plug will have a fuse.

[@danymitehazard]

Awesome I guess I know what’s wrong with my bench grinder

[@BensWorkshop]

If it buzzes like that and you can manually start it, it's either the capacitor or the connections to it. I am very pleased to have been able to help. Many thanks for watching, please like, share and if you like the channel, subscribe!

[@danymitehazard]

@@BensWorkshop thanks I’m fixing my dads grinder for myself and when you try to turn it on it makes a huge loud buzz noise but the wheels won’t spin.

[@BensWorkshop]

And if you try to spin the wheel, what happens?

[@danymitehazard]

@@BensWorkshop idk yet I’m kinda busy right now, I’ll try to work on it later and when I do I will let you know, we’ll stay in touch. 👍🏻

[@BensWorkshop]

@@danymitehazard Cheers

[@harmonica2007]

Is there any danger of discharge from a capacitor?

[@BensWorkshop]

Not a big one on an AC start or run capacitor, as they are charged and rapidly discharged. It's not like a capacitor in a DC power supply/ However if in doubt you can always short it out with a screw driver. Many thanks for watching, please like, share and if you like the channel, subscribe!

[@OldSneelock]

Hi Ben. We share a lot of common interests. Unfortunately

[@BensWorkshop]

Unfortunately? Many thanks for watching, please like, share and if you like the channel, subscribe!

[@rickynaidoo2921]

Sir . How many wires are going to the motor?

[@BensWorkshop]

There is live and neutral going into the unit, with an earth. From the base into the actual motor windings there are 4 wires in this unit, for 2 coils. One coil has a capacitor in series to create the phase shift that sets the direction of spin. Many thanks for watching, please like, share and if you like the channel, subscribe!

[@jcstevegigs]

My Black & Decker bench grinder only buzzes and won’t spin. No capacitor. Brushless DC motor. Is it fixable?

[@BensWorkshop]

What makes you think it is DC and are you sure it doesn't have a capacitor? I would suspect that it is in fact AC, it will be brushless. I would start by using a muiltimeter to check that you have power inside the grinder and that the switch works. I fixed a Back and Decker one here: kzbin.info/www/bejne/jXvLiImgYtSFrNE Many thanks for watching. Please like, share and if you like the channel, subscribe.

[@jcstevegigs]

@@BensWorkshop I know it’s brushless and DC were the only ones I saw in videos so I assumed. Good to finally know. Thanks. The switch works. I’ll link a short video if you have a second to watch it. Yes, I’ll def subscribe. Thanks

[@jcstevegigs]

@@BensWorkshop kzbin.infovUiERtRZ0HQ?feature=share

[@BensWorkshop]

Brusless motors are always, without exception, AC. Where the supply voltage is DC, there is a converter to convert it to AC, usually 3 phase and variable speed. Does it run on batteries? If it were brushless with a DC supply there would have to be a circuit board with a heat sink to turn the DC into the AC required to run the motor. Is there such a circuit board? Also, not all single phase AC induction motors have a capacitor. They sometimes have what is called split phase wiring.

[@BensWorkshop]

Definately an AC single phase induction motor. Just looked at the parts manual and it appears there are just two wires to the coils which is odd.

[@oldmanhads2043]

Any hints on what to do when the grinder wont spin at all unless you loosen the wheel on one side? Mine has a wire brush on the left. A grinding stone on the right. I switch it on and it humms but is jammed. I cant even turn it by hand. I loosen the wire wheel side, just a quarter turn and off she goes. The wire wheel itself wont spin because its now loose, but the right side grinding disc is spinning at least. Hope that makes sense.

[@BensWorkshop]

Makes perfect sense. I expect the wire wheel is missing a spacing washer. I made one for mine for stones, you can see what they look like here: kzbin.info/www/bejne/Zoi4kqCGbJ6ghsk I appreciate that you probably don't have the equipment to make one but at least you will know what sort of thing you are looking for. Many thanks for watching! Please like, share and if you like the channel, subscribe!

[@oldmanhads2043]

@@BensWorkshop - Thank you for the speedy reply. I had a look and all parts are there - but I found my internal flange has wear marks on it - its sliding in too far and rubbing against the case. swapped it with the outer one and we seem to be back up and running. Wouldnt have found this without your suggestion. Thanks again.

[@BensWorkshop]

You are very welcome. Take a look at the channel, you might find other interesting things on it.

[@fredmanda4830]

How do i connect direct

[@BensWorkshop]

I do not understand what you mean. If you mean direct current, you don't. Induction motors are AC (Alternating Current) only. Many thanks for watching, please like, share and if you like the channel, subscribe!

[@28Emanuelp]

Breh. They threw it away for a reason. It needs rewiring. Brand new one cost $40.

[@BensWorkshop]

If you don't like people fixing things why watch videos on people fixing things? 1. It does not need rewiring. 2. A brand new one of this size and quality costs a lot more than $40. 3. People often throw things away because they are unable to fix them because they think like you.