Angle Grinders - 5 Common Issues & How to Fix Them 

I changed my brushes out, both were chipped. The grinder still sounds bad, and stinks. Any ideas on whats next?

Have a look at the wires on the armature windings. The varnish can wear or get scratched and you'll get a bit of arcing which over time can get worse and result in burnt or broken wires. Look for any black sooty spots on the windings. You can buy winding varnish pretty cheap if the wires haven't yet broken and apply a little. Another thing to look at is cleaning the case very well to get rid of any carbon dust from the worn brushes (it gets everywhere) along with metal dust from grinding, both of these can cause little issues.

These are a few steps to attempt to get extra life out of the tool but eventually the tool could be at its service limit and need a whole new armature (and more) which can run about 75% of the cost of a new grinder. But I believe in trying a few inexpensive things first to be sure. Good luck!

@@nothandsomebuthandy thanks, I will try that. Its only a year old so it should work

@@nothandsomebuthandy can u check this out? I changed the brushes and cleaned the inside. It's only a year old. I stripped it down and it may be coming from the gear drive at the head of the grinder. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-A-om5o0mdQk.html

Awesome, nice to see two more tools going back into service!

Great to hear you were able to to save some!

Thank you for the positive feedback!

Hope you were able to get it going again!

Thanks, I loved that show!

You're welcome, thank you for the kind words!

Have you put new brushes in?

The rectangle piece you describe sounds like the end of a carbon brush. You likely used up the brushes completely and need to change them. Pretty easy to do and replacements aren't expensive.

Thank you, please check the link in the description I redid this video with better audio.

Thanks for the feedback!

Have a look at the cooling fan, might be getting caked with dust and causing drag. Check brushes, maybe they're worn really low and tapping mimics spring pressure that might be reduced. Lastly check the bearings on each end of the armature, they don't fail often but I do change them once in a while. Good time to take apart and give a good cleaning.

Excellent!

I would give it a good cleaning and some new brushes. Clean the commutator as well and look for buildup in between the segments. Try not to get any grease on the motor side. What brand/model of grinder are you using?

Thank you

Do you mean you use a wire wheel and the nut gets stuck? The nut gets stuck often when the wheel gets really hot from use. Do you feel the vibration if you run the grinder without a wheel or the nut on? I wonder if the wheel you're using is wearing out unevenly causing the vibration.

Thank you!

Sorry I don't have a whole lot of experience with lithium powered tools. Brushless motors are also much more complex than brushed motors with more parts that can fail such as the motor controller and rotor encoder. I also remember a lithium powered vacuum cleaner I had that would turn off seconds after starting the motor due to the battery overcurrent circuit malfunctioning. I actually have a few brushless drills in my repair bin I plan on tackling in a future video. If you do find a solution for your problem please let me know. In the meantime a local tool repair shop may be able to help you. I have one in my town that charges $25 for diagnostics and waive the fee if you go ahead with the repair.

Haha

The grease in the head may be breaking down. What brand grinder?

Actually it's 5" makita 9005b I'm working on. I'm not too familiar with the Bosch ones but "The Post Apocalyptic Inventor" often refurbishes Bosch tools and holds them in high regard. I think there is something about the shade of blue that indicates the grade of tool as well. As for grinding concrete I don't know how well protected an angle grinder would be from the cement dust as all the ones I've worked on don't have any sort of filter to keep dirt out of the motor. I know I have killed several vacuum motors with cement dust. That said it couldn't hurt to disassemble, clean everything and see if there is any real damage or if there's just excessive dust buildup jamming things up. Have you tried using a vacuum hose to pull the bulk of the dust while grinding, and maybe wetting the concrete first? I only use my grinders on metal so I don't have any experience with concrete.

I agree, I remade the video with the sound corrected. The link is in the description.

@@nothandsomebuthandy ok thanks

Thank you!

If you're talking about the stator (chunky metal electromagnet that surrounds the armature) you can disassemble the grinder, pull out the brushes and armature, and measure the resistance between the metal parts the brushes slide into. I'm not sure what the ideal resistance range should be but it should at least have continuity and be more than 0.

Oh and yes you can replace the stator, it's makita part # 520073-2 . It's held in with 2 screws, just use a screwdriver to pop the round springs off the brush holders and it'll come right out. The trickiest part is getting the springs back on but it isn't too difficult.

Does it have the anti kick back slip clutch? If so possibly an issue with the clutch slipping. Otherwise the gears could be worn. What model grinder is it?

I finally figured it out, it was a small washer that goes on top of the big gear that was broken. Its weird because this grinder is only 2 months old😢 i do have the anti kick back slip clutch

Metabo should have a 3 year warranty so you could try returning to where you bought it, or contact their customer service.

Thank you

What model grinder? It should not be difficult to spin with with fingers.

@@nothandsomebuthandy It doesn't say, it's not visible but I used it a couple times and stopped working slowly when was grinding. I think it's Black and Decker

Any strange noises or burning smell?

@@nothandsomebuthandy Burning smells yes. I'm going to open it

@Spiritusanto16 check the armature for black soot around the windings, if it gets too hot the varnish can melt off and cause the armature to short

What model of grinder? Some guards have a quick release arm and others have a screw to adjust the tension. Some also have tabs that you need to align to get the guard on, you have to install it almost 180 degrees from the normal position then rotate it into place.

A milwaukee 4 1/2 M18 cordless grinder, I did put the put the guard on 180 degrees from the correct position to get past the tabs but then it would not slide any further than about 10 degrees so that it could line up.

I remember having similar trouble with one at work before. The instruction manual shows to install 180 degrees then push the spring loaded button to spin into place.

documents.milwaukeetool.com/58-14-2602d5.pdf

Does your grinder have a slide switch or trigger? Does it have both the black and white wires going to the switch or just the black ones with the white wires connected together with a separate contact block?

@@nothandsomebuthandy Its a Makita 'trigger' replacement. Black wires connect at the bottom of the trigger, yellow conects at the top. White wire connected separately.

What model?

@@nothandsomebuthandy GA5020

I have a ga5020 in front of me and but it doesn't have a yellow wire. The power cord has a black wire and white wire, both connect to the bottom of the switch on different posts. The two wires coming from the motor should connect to the top two posts on the switch. This is assuming the replacement switch is also double pole like the original.

I'm not familiar with that brand but a quick google search I found a manual with parts breakdown. There's a number to call to order parts: 1-866-915-8626 M-F 8-5EST. Good luck!

@@nothandsomebuthandy thank you

What brand and model?

@@nothandsomebuthandy its a omegamechanix m4900/bs

I can't find any information on this grinder but looking at a photo it looks similar to some brushless grinders I've seen before which have overload protection. I have a few theories as to what could be happening: 1) you are working the grinder too hard, it is only 900w so not very powerful 2) the overload protection was calibrated at a higher input voltage but the voltage in your area may be a little lower so the grinder is drawing higher current 3) are you using a long extension cord that could be causing a voltage drop? 4) the overload protection is too sensitive 5) the grinder is defective

@@nothandsomebuthandy it has brushes, the grinder is very similar to Bosch gws 750. It only need to start grinding ant it stop working...

When it stops working does the switch remain in the on position or is it possible it moves back a little?

What type of switch does it have? Trigger, paddle or slide? Does it have a switch lock to keep it on? More than likely I think you'll have to replace the switch but if it has a lock check that mechanism first to be sure it's not sticking.

My first guess is that the windings are shorting and the varnish on the armature is starting to burn off and smoke. Pretty much end of life for the armature, but replaceable in a quality tool. If it is old or inexpensive likely time for a new one.

I remade the video with the sound corrected, you can find it here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Gvv8JqcQ0iU.html

Good to hear, you're welcome!

I'm not familiar with that brand. Have you tried charging the battery? What is the model # of the grinder? What type of wheel attachment are you using?

@@nothandsomebuthandy it doesn’t work on any wheel attachment or without it and it’s just a cordless 18v model it makes a beep noise and doesn’t spin and sometimes the motor just moves for a millisecond

What is the brand and model? Are there any other letters or numbers?

I found the grinder online and found the following in there that may help:

"This tool is equipped with Automatic Restart Protection. This feature helps prevent accidental startups after power has been interrupted, e.g. the battery was removed with the switch locked in the on position. To resume operation, turn the slide switch to the off position, and back to on position to restart the tool. Make sure that the slide switch is in the “0” position before inserting or removing battery pack. To insert the battery pack slide it into the housing until the battery pack locks into position."

Depending on how hot it got I imagine some of the Insulation on the windings could have burned off and that is allowing it to arc out. When this happens I usually replace the armature if I have a spare or strip the grinder for parts.

You might be able to see black sooty marks on the armature where it is arcing. If it is only in a few places you can reach theoretically you could apply more varnish to those areas. But varnish is expensive and really if it's burned off where you can see it it's likely also burned where you can't.

Provided there's nothing else wrong with the grinder you can get a new armature on amazon for $74CAD ($59USD), the one for a 9005B is here: amzn.to/3HDdBaq

@@nothandsomebuthandy wow man thanks for the reply!, we were all standing around wondering why we smelt burning stir foam I figure that’s exactly the problem or worse, thank you for the link! I’m going to go back in it and test everything if it’s possibly just the armature I’ll replace it but good chances it could be more it was almost enough to burn the hand when picking it up by the case, thanks for the information man!

Good luck, Let me know how you make out!

First I would pull out the armature and clean between the commutator segments. Also take a look at the windings for black sooty marks, this could indicate damage to the protective coating on the wire.

A new armature is about half the price of a new grinder so it may be worthwhile to try changing it. I have a link in the video description for one on amazon. Worse case you could probably return it if it doesn't solve your problem.

@@nothandsomebuthandy - Thank you ,I’m going to do the cleaning as you suggested ,I will let you know how I go ,thank you very much for your prompt reply 👍

Good luck!

@@nothandsomebuthandy I did the cleaning but I think I have the wrong brushes - it’s a Hitachi Koki SAT180 dual speed /950W. Still get the sparks and it’s not spinning to it’s right speed …

Does it actually turn. Or is it just a humming noise?

@@nothandsomebuthandy it turns on it spins but the sound is not the kind you want to hear coming from a grinder

@@based_male9293 any burning smells? Excess sparks? Has it been dropped?

I'm guessing this is a cutting disc but can also happen with a grinding disc, they get too hot and the nut seizes in place. Unfortunately the only solution is to use the supplied wrench to loosen the nut while holding the locking pin down. It can help to have a friend hold the grinder on the ground and hold the pin in while you force with the wrench. Sliding a small pipe on the wrench can get you some extra leverage and sometimes hitting the wrench with a hammer can help. Be warned sometimes the pin can break in extreme cases. Sometimes if I don't have a wrench I sacrifice the disc and tap with a hammer directly on the disc to attempt to turn it counterclockwise while holding the pin. Good luck and I hope you get it off!

I can't be certain but I suspect your armature windings are shorting. Pull out the armature and examine the windings closely for black marks, soot, breaks in the wire, etc. If you have a good quality grinder you want to keep you could buy just the armature online or from a tool repair shop unfortunately but it's one of the most expensive replacement parts and could cost 50-75% of the cost of a new grinder.

Stupid question but does vibrate with no disc or nut on? What brand and model? And damage to the fan?

@@nothandsomebuthandy Grinder is brand new. Haven't actually used it yet. Rattles at particular points as it gathers and reduces speed. It is this which leads me to believe the commutator is poorly balanced. The commutator has got "chunks" ground out of it which I assume was done in factory in order to balance the commutator. Nothing attached. Not even the washer and nut that would secure a grinding disc. >

I think you're right that the armature may not be perfectly balanced. Obviously some brands have cut corners on quality of parts to lower cost, perhaps this is also true about the quality control. It could also have been dropped in shipping or just unlucky that you got a bad one. Many stores where I live have pretty good return policies where you could exchange for another one, maybe that is an option for you?

@@nothandsomebuthandy You're right, it certainly *_is_* an option and one that I am actively exploring. Thanks for your interest. >

Good luck!

Have a look at the bearings, I've found some that still turned but had considerable drag that caused the grinder to spin slowly and spark a lot. The bearings are common metric sizes and quite inexpensive.

I worry about the smoking you describe, do you see actual smoke coming out or just notice a burning smell?

@@nothandsomebuthandy Actual smoke! haven't had a chance to disassemble it again to look for where it's coming from. Smell is acrid and lots of smoke, smoke was coming out through the vents up at gearbox end of the body. Burned out winding? I'm guessing the cup wheel overloaded it, probably a bit aggressive for a small grinder.

Hmm I agree it may have overheated from the wire wheel and insulation likely started burning off. Once the insulation breaks down you start getting some shorting which creates more heat and burns off even more. I suspect it may be time for a new grinder unfortunately.

@@nothandsomebuthandy The armature part is pretty cheap, I'm tempted to replace it but I'll pull it apart again and see if I can confirm what has burned out. Kinda disappointed, didn't expect a Makita grinder to die at 2 years old though

Oh the assembly and disassembly was sped up significantly but it really does not take very long. The longest step is cleaning the commutator which takes about 5-10 mins. It usually takes me about 15 mins for the average grinder when I have my work area set up with tools and replacement parts ready to go.

Thank you

Hi there, I just posted an edited version of this video where I fixed the audio so you can hear me better. You can find it here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Gvv8JqcQ0iU.html

Hi Ali, I re-released this video with the volume corrected here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Gvv8JqcQ0iU.html

🤣

Yes we do have a lot at my work but I'm sure it would be expensive enough to ship to you. I suggest checking with a local welding shop to see if they have any kicking around or maybe a local dealer or sales Rep might have some.

@@nothandsomebuthandy i have tried all of them,they are not very helpful. I even called Makita and they never got back with me. I live in Springdale, Arkansas how much would it be to ship?

I just plugged some numbers into shipping websites and it looks like about $40USD to ship, not including any customs or duties.

@@nothandsomebuthandy that's unbelievable lol

Yes you'd think Canada was on a different planet when it comes to shipping to and from the US

Yes it is. There is a link in the video description to an updated version with better sound quality.

Click the link in the description for the new version with better sound

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Gvv8JqcQ0iU.html Same video,less music

This video was re-released with the sound corrected and other edits. Watch the corrected video here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Gvv8JqcQ0iU.html

Haha none for sale, sorry :D

Oh hi 🙋

Haha sorry for the music, I'm a country fan. As for the voice level if you look in the video description you'll see a link to an updated version of the video with the audio corrected. Hope you'll check it out!

😂