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Tools - angle grinder

  • 09-05-2010 9:15pm
    #1
    Registered Users Posts: 833 ✭✭✭


    Hi all, I have a Challenge Xtreme Angle Grinder Model no. MAG5843. Had it about 7years.
    Only used for casual domestic DIY. Recently it's become difficult to start. It is not the electricity supply. I depress the on switch and nothing happens, but if I shake it a little while holding switch on it starts. The problem is intermitant at the moment.
    I guess its just coming to the end of its useful life... what say you!:(
    Thanks.


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Comments

  • Registered Users Posts: 12,683 ✭✭✭✭Owen


    Could be the carbon brushes that feed electricity to the motor. They're usually sprung, but if the're old, they could be catching, or the springs pushing them in may be beyond their usefulness. When you shake it, that could then bring the bushes into contact with the motor, initiating powerup.

    It'd cost less to buy a new one than it would to repair. Lidl are doing an angle grinder shortly.


  • Closed Accounts Posts: 241 ✭✭tiocimarla


    Could be the carbon brushes that feed electricity to the motor. They're usually sprung, but if the're old, they could be catching, or the springs pushing them in may be beyond their usefulness. When you shake it, that could then bring the bushes into contact with the motor, initiating powerup.

    It'd cost less to buy a new one than it would to repair. Lidl are doing an angle grinder shortly.
    If its the brushes, you can do it yourself as its very easy. They are usually consealed behind plastic flathead srews. First unscrew the 2 plastic screws, behind them the brushes will be ready to pop out so be carefull. Take the springs out and give them a bit of a stretch put back together with new brushes. If this doesnt work then a new cable would be my next idea. Use flex for this:)hope this helps


  • Registered Users Posts: 9,555 ✭✭✭antiskeptic


    Hi all, I have a Challenge Xtreme Angle Grinder Model no. MAG5843. Had it about 7years.
    Only used for casual domestic DIY. Recently it's become difficult to start. It is not the electricity supply. I depress the on switch and nothing happens, but if I shake it a little while holding switch on it starts. The problem is intermitant at the moment.
    I guess its just coming to the end of its useful life... what say you!:(
    Thanks.

    Just to clarify, the plastic flat headed caps behind which the brushes live are located about half way along the body of the machine, 180 degrees apart from each other. They'll be about the size of a 1 cent coin in diameter.

    The brushes are square/rectangular section lengths of carbon. If square they can go back one of four ways, if rectangular then two. it's important that you put the back the exact same way you took them out and don't mix up the sides you took them from (they've been worn into a particular shape). Consider giving the holes from which you've extracted them a blow out as well. Don't go too mad on stretching the springs.

    As suggested, the power cable itself might be dodgy - although a loose connect/break in cable would tend to give you stop/start problems during use, not just at start up


  • Registered Users Posts: 833 ✭✭✭the watchman


    Most helpful.
    Just one last thing, if need be can I actually renew brushes and if so where would I get them from and would it be worthwhile/economical to do so.
    Incidently my feeling is that the power cable is ok.


  • Registered Users Posts: 9,555 ✭✭✭antiskeptic


    Most helpful.
    Just one last thing, if need be can I actually renew brushes and if so where would I get them from and would it be worthwhile/economical to do so.
    Incidently my feeling is that the power cable is ok.

    No idea. But it's highly unlikely the brushes are worn out if occasional diy use has been it's history.


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  • Registered Users Posts: 833 ✭✭✭the watchman


    Thanks for that Antiskeptic. I'll try and take it apart this afternoon or tomorrow morning. If I mess it up I'll still have time to get to Lidls on Thurs.:)


  • Registered Users Posts: 6,250 ✭✭✭Buford T Justice


    Brushes for them are fairly standard. You could probably get Makita brushes that will suit it. (Most of the challenge ones usually came with a spare set anyway)

    That said, if you are to get Makita ones, then it might be cheaper to buy a new one.


  • Registered Users Posts: 2,632 ✭✭✭ART6


    I had an old drill (ca 40 years!!) made by a company called Selecta that has long gone. The brushes were worn out, so being a tight B* (and it was good drill) I broke open a torch battery and took out the carbon cylinder. I carefully filed it to fit the drill brush holders. The drill then ran for another five years until the bearings failed.

    I believe in recycling:D


  • Registered Users Posts: 9,555 ✭✭✭antiskeptic


    ART6 wrote: »
    I had an old drill (ca 40 years!!) made by a company called Selecta that has long gone. The brushes were worn out, so being a tight B* (and it was good drill) I broke open a torch battery and took out the carbon cylinder. I carefully filed it to fit the drill brush holders. The drill then ran for another five years until the bearings failed.

    I believe in recycling:D

    You threw out a drill only needing bearings? Philistine!


  • Closed Accounts Posts: 241 ✭✭tiocimarla


    If you take the brushes out and bring them into mcquillans or any decent tool shop they might be have spares or point you in the right direction(ring them first to ask). I got them in tallaght in a dewalt shop near the big quarry a few years back but cant really remember the directions. Also if you buy bigger ones u will be able to file them down easy enough, also did this before as advised above and it worked grand


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  • Registered Users Posts: 833 ✭✭✭the watchman


    WOW, Art 6 , you really deserve some recognition for that one lol:D
    Your obviously the sort that would cut an 8foot railway sleeper completely in half...'length ways' with a hand saw lol:)
    well done anyway..


  • Closed Accounts Posts: 241 ✭✭tiocimarla


    Just a thought, if you take the switch apart, one of the wires may need to be re-soldered. This happened with my makita skill saw a few years agoand the same thing was happening when i pulled the trigger it would burst into action for a second and then stop. poped the trigger and brown wire was loose.


  • Registered Users Posts: 833 ✭✭✭the watchman


    :eek:NEED HELP FAST. NIGHTMATE LOL.
    Machine is in bits on kitchen table. Finaly found brushes (long story)
    pics attached ...are they allright or not. I just don't know.
    Taking break for a meal, hope someone comes back real quick.
    I do not want to put it back together if new ones required.


  • Registered Users Posts: 3,695 ✭✭✭galwaydude18


    Ya they look like the carbon brushes. They don't look too worn. Is there a line on them towards the end of them. That is the indicator line as to how worn they are.


  • Registered Users Posts: 833 ✭✭✭the watchman


    2 more pics on previous post .
    Will now go and check for lines,


  • Registered Users Posts: 3,695 ✭✭✭galwaydude18


    Can you remove the black thing from that housing? If you can I would be almost 100% sure that they are the carbon brushes.


  • Registered Users Posts: 9,555 ✭✭✭antiskeptic


    :eek:NEED HELP FAST. NIGHTMATE LOL.
    Machine is in bits on kitchen table. Finaly found brushes (long story)
    pics attached ...are they allright or not. I just don't know.
    Taking break for a meal, hope someone comes back real quick.
    I do not want to put it back together if new ones required.

    Hmm..

    Was there no access to the brushes from outside the machine? Sorry for saying there would be - generally that's the case. But anyway...

    You've got the 2 brush holders out - with a spring loaded brush in each of them (rectangular by the looks of it). To my mind the brush looks a bit on the short side but then again, the holder itself is pretty short so it could be the brushes are fine.

    Do you see what the brushes contact? It's a cylindrical, segmented copper called the 'commutator'. Basically your feeding electricity from the mains, through the brushes down to the commutator and into the motor windings. The commutator rotates as the motor turns.

    You can appreciate that when in use, a good portion of this brush would need to be contained in the brush housing in order to ensure the brush is held straight and true. In other words, if the brush isn't sufficiently contained by the housing, it would tend to cock sideways if you happened to rotate the cutting disc with the motor stopped. This cocked-ness would break good, straight-line contact between brush/commutator = no electricity fed into the motor = motor doesn't start. You giving it a light tap would uncock the brushes = contact made with the commutator ... and off she goes again.

    The way to check things would be to see if you can re-install a brush/holder and look to see what portion of the brush protrudes out of the holder when its back in place. Get a good light on things and rotate the motor by hand (by turning the grinding disc) back and forth ever so slightly and see if the brush is rocking back and forth in its holder.

    It shouldn't be..

    Is there a nice sliding fit between the brush and it's holder? Easy up and down movement but little room for rocking side to side (if the fit is sloppy, there is room for gentle crimping of the housing to get tighter (but not too tight) fit - if you find that brushes aren't available + you have the sensitivity of hand not to overdo it)


  • Registered Users Posts: 2,632 ✭✭✭ART6


    Antiskeptic refers to the commutator, and that might be the root of your problem. Angle grinders operate in a fairly hostile environment where abrasive dusts often get drawn though the motor with the cooling air. That can gradually wear down the commutator bars until the insulation between them stands slightly proud of the metal surface -- I've known that to happen many times over the years. Any time I replace brushes (and in this case they don't look as if they need replacing) I always skim the commutator. To do this I hold it in a drill and polish the surface of the bars with very fine emery cloth -- only a light rubbing is needed, but it is vital not to touch the wires coming out of the bars, so great care is needed. Having polished the copper bars, a small flat screwdriver edge should be used to scrape the insulation between each of the bars so that is is slightly below the bar surface. Again, careful not to damage the wires.


  • Registered Users Posts: 320 ✭✭RichieO


    Try changing the cable, and check all the connections....


  • Registered Users Posts: 833 ✭✭✭the watchman


    Hi everyone, Many thanks for all your help it was appreciated but I'll be off to Lidls on Thurs.
    I never want to do that again. 6 1/2 hours. My first problem was that I saw no way that the grey handle/housing was in 3 pieces and came apart. it looked one piece so I took head off 1st and only then realized that the grey housing must be in more than one part because still could not get to brushes. Searched the net quickly and rang local hardware store ,couldn't find replacement brushes. So called it a day. Then eventually trying to get the thing back together was also a nightmare - I really don't think that the chinese want us to take them apart.
    Now its back together and doesn't work at all, just makes a loud buzzing sound and turns intermitantly about 1/3 revolution...as I said earlier...'Kaput' lol.
    So I am now going to entertain you with the 'show' in pictures over the next couple of postings..enjoy, and don't laugh too loud. Thanks again.

    Challenge Xtreme Angle Grinder MAG5843....The Show....


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  • Registered Users Posts: 833 ✭✭✭the watchman


    continued..................


  • Registered Users Posts: 833 ✭✭✭the watchman


    again ...stop laughing!


  • Registered Users Posts: 833 ✭✭✭the watchman


    I thought I told you to stop laughing...........
    well thats it.
    bye for now lol:D


  • Closed Accounts Posts: 241 ✭✭tiocimarla


    Well, i did laugh a bit im sorry but they made it very hard to change brushes. This makes me think that maybe they are only made to last 4 a short time. If they wanted the grinder to be servicable then the brushes would have easily removable. From the photos wiring look ok and the brushes seem fine but the spring could be stretched a bit to force contact. Also the grease behind the blade housing seems like its all to one side and im not sure if it should look like that. Emm... If you are going to buy a new one then id firstly give springs a stretch then id open the switch housing(little white box with button) and ensure the wires are connected... its very common the solder comes loose in these. If its getting thrown out id satisfy my curiosity. If none of these work chuck it in the bin and get a new one. Iv attached an image of grinder. Just make sure the one you buy has caps like this one. At least it will be made to service easily. Good luck:)


  • Registered Users Posts: 2,632 ✭✭✭ART6


    Photo D30 explains everything. It's got no motor in it:D


  • Registered Users Posts: 6,250 ✭✭✭Buford T Justice


    tiocimarla wrote: »
    If they wanted the grinder to be servicable then the brushes would have easily removable.

    Not entirely true. There are a few Makita grinders out there that have the same handle design that need to be removed before you can access the brushes.
    tiocimarla wrote: »
    Also the grease behind the blade housing seems like its all to one side and im not sure if it should look like that.
    Happens for a number of reasons. Motor spins one way only, so will throw the grease only in one direction.
    Over time, as grease gets older it starts to congeal inside the housing and begins to form shapes like what you've seen there.

    If you don't use the machine very often, it will start to solidify. Grease is far less viscous when its hot, so if it doesn't get used much it will stick where it is, and with no heat it won't move.


  • Registered Users Posts: 9,555 ✭✭✭antiskeptic


    I thought I told you to stop laughing...........
    well thats it.
    bye for now lol:D


    Bet you had some fun all the same. :)


  • Closed Accounts Posts: 241 ✭✭tiocimarla


    Not entirely true. There are a few Makita grinders out there that have the same handle design that need to be removed before you can access the brushes.


    Happens for a number of reasons. Motor spins one way only, so will throw the grease only in one direction.
    Over time, as grease gets older it starts to congeal inside the housing and begins to form shapes like what you've seen there.

    If you don't use the machine very often, it will start to solidify. Grease is far less viscous when its hot, so if it doesn't get used much it will stick where it is, and with no heat it won't move.
    I see, well at least i learned something today


  • Registered Users Posts: 1 landlubber2


    I have a challenge extreme 9" grinder,10 yrs old but hardly used !it was playing up after cutting 3" slate for 2/3 hrs (shake to start!) so i changed the brushes as per manual..except in my haste and a phone interruption !!! i had only changed 1 brush plugged it in fired it up and it worked. realising my error i unplugged and wired up other brush.( the new brushes came with the grinder). I fired it up and now isnt going at all..i have checked fuse,checked cable and power to and after switch with ac test meter and its positive,, theres power goin out to motor. whattave i done? :confused:


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  • Registered Users Posts: 2,632 ✭✭✭ART6


    I have a challenge extreme 9" grinder,10 yrs old but hardly used !it was playing up after cutting 3" slate for 2/3 hrs (shake to start!) so i changed the brushes as per manual..except in my haste and a phone interruption !!! i had only changed 1 brush plugged it in fired it up and it worked. realising my error i unplugged and wired up other brush.( the new brushes came with the grinder). I fired it up and now isnt going at all..i have checked fuse,checked cable and power to and after switch with ac test meter and its positive,, theres power goin out to motor. whattave i done? :confused:

    There might be power going to the motor field windings, but that doesn't mean it's getting to the armature. Most likely reason is that one or both of the brushes is not making proper contact -- probably sticking in its holder (or in your haste you left a spring out!). I would take out the rotor, clean the brush holders, and make sure that the brushes can both move freely right down the holders.


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