Easy Power Tool Fix: Burnt Commutator

Sparking motor? Think your tool is broken? If you bound up the blade of a rotary tool of any kind this fix may be all you need. Even if you smelled smoke. Check your brushes to see if they need to be trued up or replaced as well.
A new to me circular saw (Black and Decker 7391 type 4) was sounding awful and sparking badly out of the vent when run. I opened it up and was delighted to see it was just a moderately burnt commutator on the motor's armature. Aside from that it was perfectly fine. A few minutes with a few cents worth of 1,000 grit automotive sandpaper made a world of difference. The tool was fully torn down, repaired and reassembled in less than a half hour. That's the type of fix I like!
On to woodworking!

[@penguin6636]

It's moments like these that truly appreciate how popular utube has become. Thanks for the tutorial!

[@narekdiesel]

If. Only it stayed the same huh

[@randomeddie185]

i would also recommend a thorough cleaning of the commutator after sanding, including a very careful scraping of the slots in between the copper pads. i have seen people leave copper residue from the sanding process in those slots, which creates an electrical bridge between the pads. another important reason to clean the slots is because material that has been eroded away from damaged brushes can build up in there and will also act as an electrical bridge.

[@DumitruUrsu]

Also, a word of caution when cleaning the slots - don't do it with a screwdriver! Use a tootpick, or some other soft material - with a screwdriver you risk to bend the edges, and make the sharp and raised - it will eat the brushes in minutes!

[@rubengarcia8251]

Good to know it man, thanks

[@HolyGrailOfGolf]

I have this same motor in a leaf blower that runs horribly. I've tried servicing the commutator and brushes but it still runs horribly and heats up quickly. Any idea why this thing runs so badly?

[@pjanse11]

SHE LIVES!!!!!! My Lidi/Parkside mitre saw is alive again! I couldn't rely on Lidl for support, but thanks to you Ian, i'm cutting skirting and floor boards again, wohooo!!! The wife is almost as happy as I am!!! :D

[@BRiTORC]

Omg! I used to make those armatures at Black and Decker Spennymoor UK,!! The commutator is turned on VEE blocks with a diamond tool,so its perfectly concentric with spindle. Too smooth a finish on the copper can cause sparking so use quite a rough emery or sand paper to clean it up with, then finish off with a wire brush , taking care not to damage any of the resin or varnish that binds the wire in the motor together. The copper segments are separated by a non conductive plastic and can become clogged with material, this can also cause sparking (usually accompanied with a high pitch noise), again clean with a wire brush to clear them. Never use compressed air to blow out electrical motors (of any kind) as this just moves contaminants into places they should not be, and you cant get access. As a rule of thumb,if your electrical appliance starts giving off any kind of smell that's not normal, or overheats quickly, then its probably dying, but on the other hand if it sparks but gives off no smell then its probably worth taking apart and cleaning.

[@ZevHoover]

+Kevin Seal wont excessive sparking often be accompanied by an ozone smell though?

[@IanSlatas]

Very cool! Thanks for sharing.

[@neilfroggycrompton2466]

+kevin seal thanks for the info,are replacement brushes needed too?

[@GezaShad]

"Too smooth a finish on the copper can cause sparking so use quite a rough emery or sand paper to clean it up with, then finish off with a wire brus" Ian mentioned 1000 grit sandpaper, you suggest "quite a rough" ones. How rough, expressed in grit? Since I'm no expert, I am really not trying to start an argument here, but why would a perfectly polished commutator would start pulling more sparks than a more rough one?

[@AdamCchannel]

If the surfaces are too rough they could grind the brushes though.

[@herberar]

Nice job Ian ! I ve doing this for years,and just put the armature in my drill press chuck to achieve a nice concentric polishing. I also use a straight piece of wood to back the abrasive paper so as to keep the sides as paralell as possible . Thanks for sharing. Cheers !

[@102ferg]

i used your video to repair our washing machine, there was voltage reaching the brushes but it wouldn't spin so i took the 470 Watt motor apart and cleaned the commutator, it was blackened, and now the machine works good as new!

[@Gsauce08]

@g quinn with a cleaner

[@rachelrodgers9171]

This can also apply to electric Weed Eaters. Especially ones where the brushes are easily removed. I've replaced my Weed Eater's brushes and cleaned up it's commutator on occasions. Also after each use, I take my Weed Eater apart to clean whatever debris gets into it from underneath as well as into it's vent slots. That is why my 39 year old Weed Eater brand grass trimmer is still running like an athletic champion to this very day.

[@AdammP]

You should just put the shaft in a drill chuck and hold the sandpaper on it. Youll get much more even results

[@AdammP]

@Abdullah Brandon turd

[@joshklingman3179]

I have 3 of this saw and absolutely love them. The first on was $10. the second was $6. and the third was $9. and the hand grip still had textured grip not worn smooth from use.

[@shoestringeng6473]

Great Vijayo! I think I have at least two of those saws bought them 30+ yrs ago. Back then if you got a good sale you cld get them for about $29 USD. They were the lower end of consumer market but mine are still running today. You can probably buy a new saw for the same $29 today from the Harbor Freight type of store. in some ways it may be new and better but I still feel like the older product were build a little more robustly thus you could service some new life into them like you did here. The newer tools seem to be made in such a way that you can't really service them. Rarely does it actual pay to do these repairs if you place any value on your time but IMHO there is no better feeling than when you fix something like this and bring it back to life! The more of these jobs you do and try the more you can do and the smarter you get! Good Job my Friend!

[@diwanm2012]

hi sir , i watched your video, u ran the motor after sanding the commuters, but running it at full speed will show how successful your work was, at low speed it won't show much ,but at full speed it will show all

[@AllTheGoodHandlesAreGone]

Mate got to say big thanks for the tip.!. My $1200 dewalt mitre saw started sparking and making a bubbling sound then completely died 1/2 way through a job the other day. Pulled the back off it and the commutator was completely burnt out. I did your trick with 120g (very gently) then 1200g paper while it was still attached to the saw, it came back to life, almost as good as new. I say almost as it sparked a little and the commutator blackened slightly quickly but I think the brushes are shot. I'll order new brushes and clean the commutator up again and reckon it will be good as new. You saved me $1200, I thought I was up for a new saw, $1.40 for some sand paper and 15 minutes, lifesaver. I now know it was all my fault, I pushed it a bit too hard through a big board with an average blade, overworked the motor and burnt it out.

[@putheflamesoutyahoo1503]

did the motor smell and smoke also? I pushed my 2.5 skil saw and it died smoked smelled. Not sure if bushes would revive it.

[@AllTheGoodHandlesAreGone]

putheflamesout yahoo I say have a go you have nothing to lose. Clean the commutator and try it. The only reason I changed the brushes was as soon as I cleaned the commutator my brushes sparked a bit and darkened my commutator again. I cleaned it once more, replaced the brushes and happy days, never thought about it again. Good luck, brushes are easy to find and really cheap delivered from E bay...

[@melsondemel2739]

mame kemethi seme theyakme liyanne berithe?

[@melsondemel2739]

mage me rate kavetheavth thiyunuceranne be.be horuwede nesa mame harethe?

[@kw0s]

My 2007 Nissan Frontier power window has similar issue. Between the copper electrical contacts, it was filled with worn carbon brush dust. I clean it out with a pocket knife and good as new again.

[@krystleroy3068]

My motor smells like old metal and over heats I haven’t opened it up yet but I do believe the commutator is the problem and for the smell

[@sewingmachinesindetail]

Thank you for your good video. I got a universal motor too on a sewing machine. I noticed, that the torque from the motor was very much dependent of position of the armatur. Furthermore, when I turn the motor by hand, it sound from the commutator do not sound right. I took it apart and noticed more burn marks on commutator as you have got on your motor. But I sanded it down with 2000 grit sand paper. I also have an ohm meter and checked all connections, and the got they same value. Then I assembled again, but I do not notice any change. I still got significant torque changes with position. I got other similar sewing machines motors, and they do not vary so much in torque. I have also noticed, the wear on the end of the brushes. It seems that only about half of the brush connects on the parts that receive the commutator lamels. Perhaps the part with leaving lamels are partly broken off. So perhaps I need to wait for the brushes to wear a bit more with the "new" commutator, so it they make better connection again.

[@nowvalleydiorama885]

I can see the smile on your face from here, well done and thanks for sharing. Wayne from Australia.

[@ronmartinmhg2804]

Thanks for the video. I thought my old B+D hammer drill was on its last legs, with sparks and something like a flapping sound. Mind you it had been submersed in the floods here in Thailand a couple of years ago. I am not good at electrics but did as instructed with the commutator which was black. The brushes seemed to be OK but then I don't really know what I am looking for. The hardest part was removing the casing screws,but other than that it was easy and works OK. A few sparks but nothing like before. Thanks again.

[@lissettelopez8331]

holy crap, I have that EXACT same saw in my shed, and I bought it used. It runs horribly and I'm betting it's the same problem.

[@zx8401ztv]

Smashing job :-D No better feeling than recovering a usefull tool from the grip of death :-D Hope its still working for you :-)

[@IanSlatas]

+zx8401ztv Almost two years later and it's still seeing use several times a month!

[@zx8401ztv]

+Ian Slatas Brilliant :-D, well worth the effort :-D

[@lukehome9762]

I fixed my hammer drill doing the same procedure. Thanks

[@woodworks3585]

Nice Job. I have done this repair many times over the years and has saved money because of it. Great job.

[@nameinvalid69]

my grass trimmer is smoking up at these contact surface & loosing power / won't spin. yeah mine is full of black trails on the copper. So they are the culprit and can be fixed with just sanding them up nicely? ok I try it again next time. Thanks!

[@daviddavis5689]

Its best if you have a electric motor shop nearby to have the commutator turned. But at least when changing brushes use a plastic safe electronics spray cleaner to flush the commutator.Brushes are cheap so change them more quite often.

[@LilNyu]

Just got myself a B&D circular saw, different model but overall same one as yours, got to service it now I'm just missing the carbon holders

[@GezaShad]

Ian, this is a very easy to understand video! In the memo section you said "Check your brushes to see if they need to be trued up or replaced as well." How can you tell that one or both of them need to be trued up? How do you do that?

[@dreazy3683]

ur a life saver mate some guy at work fkd mine safe to say dunno why it’s broke now i know and it’s pitch black i’ll fix this tomorrow stress off my back

[@danniemarcos3107]

Thanks a lot for this tip. I will try this quick on my B&D power drill tomorrow.

[@masterbaiter141]

My backpack vacuum cleaner is doing those sparks, I'ma try cleaning the contacts see if that works, that'll save me $100 motor replacement if it does the job.

[@MrStonedgolem]

It work?

[@tomleary6914]

Nice video Ian. Easy to understand and follow.

[@rogerhammond3344]

Winner Winner Chicken Dinner ... Good as new again ! Got yourself a good saw again 👍 Reminds me of me fixing my cheap lil Ryobi 18.0V Circular Saw ...

[@Mrjimmybuckets24]

My Bosch 4000 table saw is sparking like heck and rpm's are all whacked out. I cleaned the brushes and armature really well just like you did in the video, but it had no effect on the overall problem. Still sparking really bad, chattering, and rpm's still out of whack. I believe its either the armature or field coil that is the culprit. However, the armature looks really good as well as the field. I would hate to dish out $150 for both items when it could just be one of them causing the short...

[@IanSlatas]

James Johnson Are the brushes past their usable life? Maybe there's not enough spring pressure on the brushes? Is the brush contact surface the correct shape? Are the bearings and bushings on the armature snug with no play? I'm with you on not wanting to throw parts at it. I hope you can fix it!

[@noel6810]

My B & D power drill sparks when it turns the brushes still looks good what do you think nis the problem

[@Mrjimmybuckets24]

charms robles Could be several things: Fried armature, fried field windings, or fried circuit board if there is one in the drill. But, it could also be the brushes even if they look good on the outside. My bosch table saw was arcing pretty bad and brushes look surprisingly good, but the armature and field windings turned out to be in good shape and was told the speed control (aka Circuit board) could be the culprit. I will also buy new brushes because they are the most inexpensive fix out of the parts.

[@Mrjimmybuckets24]

Ian Slatas The brushes are a little burnt around the springs but not the brushes themselves. My armature and field winding turned out to be in good shape. I will order a new speed control (aka circuit board) and new brushes to see if this will fix the arcing and speed fluctuations. About $40 for both sets of items. Thanks for the help!

[@dr.lauranolagato1086]

James Johns on

[@edhowcomedamianofranco7849]

Can the bearing that are not centered or the screws that attached to hold this in place or how tight or lose mite be a factor of causing it to spark ?

[@FathersUnitedNow]

Is it easy to disassemble and how to you remember where everything goes back....great vid

[@charg1nmalaz0r51]

know this is super late but the best thing to do is take pictures on your phone as you take it apart and then go in reverse order when putting it back.

[@4vinos]

I have a 10 inch table delta drill press that stopped working. I placed a magnet on the motor to hold my key and some sparks flew out and the motor stopped. Did the magnet negatively affected the motor? If so, how can I fix it? Good job and I sure hope you can tell me what to do. Thanks.

[@tareqzakarneh221]

thanks for your tip I will 1000 sand paper , I was going to use with my hitachi the 2000 sand paper

[@henrikjonsson4340]

Tried this but mine is a 18 volt cordless drill. It is still a lightning from the back. Tried to sandpaper down the coal it got better but on a higher rpm it went as the same again. Anyybody?

[@andrewsotnikov5680]

What gritness of paper is better to choose for cleaning car's starter commutator?

[@bsa5650]

Hi great video and thank you in advance. Could you please tell me what you would do to clean the brushes i.e. any build up and roughness? Many thanks SJ

[@zakkimo249]

hi, my drill motor smoking, sparking at the end part of the motor where carbons get in touch whith the motor . what do you think could be the problem ? How to fix it if it is possible . THANK YOU .

[@bidders77]

great video, i was hoping you could help me, my corded hammer drill stopped working, i think i put it under too much load so it made a funny smell and then won't rotate anymore. It has an led in the handle which indicates it's still getting power, the drill has only had possibly 4-5 hours total use over the 3 years plus i've had it so should be plenty of life left in it. do you have any ideas as to what the problem may be?? thanks, Ian.

[@startazz]

I've got a Dremel and i'm hoping this might help that too,i used it today and it stopped working and got a little too hot,i took it apart gave it a good clean and the brushes look fine to me and not worn out,but when i power it up all i get is a buzzing sound,like the motor is trying to spin but won't,any ideas????? oh and my copper plates on the armature are really black too. I'll try this if i don't get a reply and report back in the next couple of days.

[@isakwilkinson2491]

It's pretty awesome. I wish we still made things like that in the United States they they were made to be serviceable all of them. Or do it yourself serviceable. But it's like a lost and forgotten art the new generation meaning my son and my nieces and nephews who are varying an age 19 years old and my son is in his 20s they don't want to know how to do this stuff I've tried to push it on him they don't want to know they just said we can just buy another one. And I just laugh and I go are you serious. Save yourself some coin learn how to fix it learn how it works. I'm 50 years old and I'm just thinking all the infrastructure that's around our country United States it's just going to fall apart and these kids are going to go we can just buy another one I don't know it bothers me but thank you for the video keep making great videos

[@sicnarf36]

i think i could a little spark still there.. is it normal?

[@shelby50411]

Hi.. i have a craftsmsn router keeps turning off due to sparks..i took apart and filed the commutator good on a lathe and then i flattened the brushes good and now it works a bit better but powers off at high rpm setting...sparks...anyone have any suggestions..brushes are about 1/2 in long

[@paulh1860]

Could I ask if the sparks made a sulphur smelling smoke?

[@ahmedsaied2348]

what cause the spark and smoke inside jigsaw pls sir

[@meryemsheraz7924]

I checked everything It doesn't work...Please help!

[@Hamptonacres1]

Interesting video. Thanks for sharing.

[@JohnDoe-gm5qr]

That reminds me of a lawn mower that was difficult to start. It was an unbelievablye easy fix. It only needed oil! It amazes me that the guy who gave it to me seize the engine because now it has gone from being the dreaded multi pull piece of junk that no one wants to use to a one pull start mower. It probably helped a little that I flushed the oil with some transmission fluid with a little engine flush and a bit of decent synthetic oil. Just put that concoction in the crank case and run it a few minutes and drain. Afrer that put in some new oil along with a little bit of an additive not found in stores or any place local for that matter. It is not something containing Teflon or chlorinated molecules of any sort but leaves a slick coating behind. Chances are you may not even know the brand of the stuff I used but it is one of those products the skeptics are quick to call snake oil. All I can say is I have used it in my car and it now runs smoother so they can take their snake oil and shove it where the sun never shines. I hate people who knock a product without having tried it. It is because of that some of these miracle products never catch on and sadly the makers of them go bankrupt. Just to prove that I am not selling anyone's products, I won't mention the brand and advertise for them. They do not pay me anything anyhow. If you are into this stuff as much as me, a little research may have already helped you find it or something like it.

[@perthcorrespondent5812]

+John Doe Ummm cool story bro ... ???

[@ronniebostic1343]

I asked how to disassemble a black& decker 75th anniversary electrical drill no.7191A black in color,& it shows me several drills but not the one i have. I need to know how to take the front off so I can take the motor out, does anyone know,& could tell me. Please & thank you, (disabled veteran)

[@moedem]

I’ll try this on my sds drill later much thanks 🙏🏾

[@TheLoobis]

Hmm. sanding it down. I'll have to try that.

[@jessenurse9194]

Be good if you had a lathe or something, although it looks like it would be more or less even

[@mg1881]

very nicely done video - thanks!

[@johndevenny3454]

thank you sir

[@flyingnukes]

TO START MOVEMENT ON MY LATHE I HAVE TO SPIN IT TO MAKE IT GO. ONCE IT'S SPINNING THE MOTOR TAKES OVER AND IT WORKS FINE. ANY IDEAS??

[@FrancisKoczur]

Starting Capacitor

[@TheMeyera]

tanks a lot !

[@stephboeker7835]

Great video , content and production ! :) I was hoping you could help me w/ an idea I have ? I'd like to add a variable speed switch to my bench grinder in order to run it at slower speeds. I've noticed many amp ratings for these switches and most will work fine on a 5 amp motor. Question: 1.) Will I risk damaging the electric motor on my bench grinder? 2.) If okay to add switch, should I try to match the amp level or would a higher amp rating switch be just fine? 3.) If I get a variable speed bench grinder that supplies 2000rpm's to 3400rpm's , could I theoretically add another variable speed switch in order to run it even slower than the minimum 2000rpm's ? Thank you for your generous consideration, Steph

[@IanSlatas]

Sorry. That's beyond my level of understanding. Hopefully someone else can chime in with an idea. My instincts would tell me that a higher amp rated switch would be fine if they're like switches I'm familiar with. Some motors have trouble keeping themselves cool at lower speeds if the fan isn't rated to operate efficiently at those levels. Similar to how a drill at low speed needs frequent breaks. I don't know what speeds you have in mind and it might not be a problem. Good luck.

[@elesjuan]

Bad news is using a triac or motor speed controller to adjust the speed of a bench grinder or other AC tool motor is you'll lose a lot of the motors torque at the lower speeds an result in a greatly increased wear. Don't recommend.

[@stephboeker7835]

Thank you.

[@LLuE88]

is the "sandpaper" used here actually "sand paper or a carbarundem variety? " I've told since first acqainted with working on commutators that only real sandpaper is to be used. regards

[@IanSlatas]

I used an automotive wet/dry "sandpaper". Yes, the paper was coated with silicon carbide and not 'sand'. What you learned may be correct, I can't say (is there a concern about remaining dust being conductive?), but the tool was given to me broken so I used what I had. Brushes and copper are conductive and they both leave dust as they wear so maybe conductive dust isn't the issue. If it's already broken, why not give it a shot? I just used the saw to cut plywood and batten siding to resheath a very old existing building that had wonky walls and odd spaced supports. The saw saw a ton of work the last two months (hours per day on occasion) and is still 100% fine. I really wish I had a track saw now, haha!

[@IanSlatas]

Your comment piqued my interest and I think I found the answer in a 1920's railroad signal engineer text book. Of course it would be there! The concern seems to be the durability of the silicon carbide grit and that any that remains on the armature would be "continuously abrasive" relative to significantly less durable silicon dioxide if it were embedded in the armature or the brushes. I did take the time to wipe it clean because common sense would say any abrasive on an armature is bad news. Still, it's a point worth noting and if I ever have some downtime again in my life (ha!) I'll take it apart and check for track marks in the armature from grit stuck in the brushes and visa versa. Thanks for forcing me to learn something new! Of note: The armatures referenced in the text book were of a scale magnitudes larger than our little rotary tools but I'm sure it's still relevant. It's also magnitudes easier for us to thoroughly inspect every square inch for debris before reassembly.

[@LLuE88]

thanks, regards

[@apextools8144]

Nice video!

[@JasonMcGinn]

Sweet! Thanks man!

[@JoeGassen]

You are resourceful if nothing else! JK, Great work!

[@IanSlatas]

Nailed it. Nothing else. haha

[@britesynth]

did this on my 4.5 amp jigsaw but still creating sparks =( help

[@IanSlatas]

Check your brushes and the springs that keep them in contact with the armature. If the brushes are worn or the springs are weak or nearly fully extended the brushes could still bounce. If so, you may want to try replacing them. Also, depending how bad the armature was a little sanding may not fix it. Good luck!

[@britesynth]

i'll try replacing the brushes first,

[@heathbarker3004]

SWEET.

[@hectorgalvan8674]

Cool vid thank you

[@MikkosFree]

Just asking, but was that still a spark at 3:59?

[@brylelee4833]

yes, every motor sparks just a little at the commutator

[@john619hac]

Mikhail Galatinov it's spark when you start machine

[@jasonhounsell3297]

As comments below said, it will spark as its going from 0-60 in no seconds :-) I repair washing machines, and sometimes I run tests on the motors outside of the machine, and you see plenty of small sparks as it revs up without a tacho to monitor the speed.

[@MikkosFree]

Cool. Thanks.

[@bulletbasu9728]

Tnq u so much

[@seanmcaleavy2369]

I don't mean any offense, but if that circular saw is a step up then your old one must have been a real piece of shit. But on a more positive note, this was a good "fix it" video and I appreciate your effort.

[@IanSlatas]

Haha! No worries. I was a newish homeowner. I have a Makita track saw as my main panel saw now. Thanks for caring!

[@seanmcaleavy2369]

@@IanSlatas Nice! Now I'm envious. Peace

[@annareuter7639]

Why is a circular saw a "SHE?" Did you use electronic cleaner to wash away the sanded residue?

[@curiousgeorge555]

@Anna Reuter , You haven't heard men call their cars, tools and so on she? Serious?

[@annareuter7639]

@curiousgeorge555 I don't refer to my stove as "he." Machines or tools are all neuter gender.

[@curiousgeorge555]

@@annareuter7639 Must be a drag to be so caught up in such a a non creative, non imaginative, politically correct world.

[@ramchinna1534]

Sri datta power tools super am

[@ugenegareth9339]

2 Esdras 7:100

[@912ruckus2]

You did not repair the bad connection so it's going to burn out again soon.

[@IanSlatas]

Maybe? This was over 6 years ago and it's still my go-to saw for rough cutting panels or sheet goods. When it's finally retired I'll be ok with that.

[@andIloveH]

Nice work and thanks for sharing

[@ramchinna1534]

Sri datta power tools super am