chop saw dead

[yarpap]

any one good with sparks?my chop saw makita 2414 keeps taking out the rcd in the workshop yet its plug fuse is ok, some times it spins up for a second or so other times tripes straight away lots of prety blue sparks from the brushs
could do without expence of replacement
Dave

 

[yarpap]

sorry my spellings are as bad as the chop saw

 

[Mikey D]

Has the saw had much use ? Are the brushes worn out , theres usually just a screw cover holding the brushes in place ....take em out and have a look

cheers mike

 

[yarpap]

the saw is well used!! bushes are as new,checked it out with meter cant find any short or fault just one of those mysteries, no one wants to repaire these days i get told to sling it and buy a new one
dave

 

[Mikey D]

In that case plug it into a non rcd'ed circuit
and hope it doesnt

 

[yarpap]

working in a dairy tomorow may plug it in ther and ask the apprentice to try it, it may stop him moaning about the cold!!

 

[rtbcomp]

Assuming you mean bRushes rather than bushes, two different things altogether, blow the carbon dust out with compressed air. If there is a short from brush holder to earth it will trip the RCD.

 

[Wozzaaah]

the saw is well used!! bushes are as new,checked it out with meter cant find any short or fault just one of those mysteries, no one wants to repaire these days i get told to sling it and buy a new one
dave

When you say the brushes are as new, do you mean they just look like they're new or have you compared them to some new ones? You may be surprised how long they are supposed to be. Also, if they've got hot, the brush springs may have weakened which will cause arcing. Chopsaw motors get a lot of abuse, the temptation to put more pressure on the handle to cut quicker will seriously shorten the life of them.

 

[Drains]

Have a good sniff of the motor... I can't describe it, but you can tell when it smells like the rotor's burned out.
Or the commutator could have overheated and warped.

Woz is right - i've seen loads of chopsaws killed by being overworked and overheated - very easy to do once. You need to be a plonk to do it twice though.

 

[yarpap]

the "brushes are new", theres no nasty smells, well there was when the rcd went but that wasnt an electrical smell! rotor runs free,tis one of those mysteries.
dave

 

[rtbcomp]

Just a thought. Is there a supressor somewhere in the machine? These are usually connected to live, neutral and earth so it could be quite possible for one to develop a leak between live & earth, thus tripping the RCD.

 

[yarpap]

yes theres a supressor in the handle next to the trigger,ive been given another saw same make model etc from a work mate we had the idea of using one as parts the bl**dy thing only does the exact same thing,i tried the saw at work this morning and same again starts to go then trips out the breaker with some prety blue flashes from the brush end of the motor

 

[burntmebonce]

try taking the brushes out and have a good look at the comm if need be get some contact cleaner on a cotton bud hold it on the comm and turn the motor by hand it may be there is loads of kak on it just make sure the cotton buds are new and not all fluffed up

 

[Wozzaaah]

If it's tripping the RCD then like rtbcomp says, there must be a fault inside somewhere, take apart what you can, give it a damn good clean and look for any signs of damage. I bought a 'cheap' chopsaw off the bay of E a few years ago, it was absolute crap, kept popping the 20A mcbrcd that supplies my garage whenever I 'worked' it a little too hard but the plug fuse never blew. One day it started throwing sparks out of the motor casing and making an almighty racket. The brushes has got so hot that the springs had very little life in them so I fitted the spare set of brushes. A few cuts later, sparks out the side, breaker popped again, it's now in the bin. I know yours is a Makita but you may find it's just not economical to repair it.

 

[yarpap]

yep off to the tip in the morning

 

[piman]

Hello Dave,

RCDs are very sensitive, typically for socket circuits 30/thousands of an amp imbalance between live and neutral will trip it. So look for any poor insulation in the cable\plug \dust in the handle about the switch or just dampness.

 

[yarpap]

hi piman, tried both saws in a workshop with 32a breaker and no rcd both saws tripped straight out as soon as the triger was pressed,i think for the time and hassle i may as well scrap them ive been looking at the evolution chop saw as the makita is noisy and dusty at the best of times,off out to see the accountant this morning as its tax time, then off to pick up an old donkey saw for the workshop,i need to find a unit as i am running out of space..2 lathes pillar drill donkey saw band saw and two useless makitas in a fir tree

 

[piman]

Hello Yarpap,

not worth fiddling with then especially as it's not a hobby, time is money etc.

Alec