Can I ask, electric sanders etc

[plantlife]

I've tried the search function, but to no avail.

I've recently had a random orbital sander go quiet on me. I've stripped it fully down, everything look ok.

I've checked the brushes, seem ok. Replaced fuse. No joy, my grinder did the same thing. Changed brushes on that, made no difference?!?

Is it goosed, or worth changing brushes. I know I've broken grinders before, when they smoke, but not for tools just going quite....and there's nothing left?

thanks
Andy

 

[piman]

Hello Plantlife,

make sure the brushes are free in the holders and have enough spring pressure to press onto the commutator. After that have a look at the switch, it could be faulty, check with a meter if you have one or else short the terminals out. (Live to live and neutral to neutral, not live to neutral). The other thing is a damaged cable from the plug to the tool.

Alec

 

[plantlife]

Hello Plantlife,

make sure the brushes are free in the holders and have enough spring pressure to press onto the commutator. After that have a look at the switch, it could be faulty, check with a meter if you have one or else short the terminals out. (Live to live and neutral to neutral, not live to neutral). The other thing is a damaged cable from the plug to the tool.

Alec

Hi Alec,

Never thought it might be the switch. The cable and plug look in good condition. I'll double check the brushes too.

thanks for the tips
Andy

 

[KemppiFrog]

I have six small grinders in a box to fix from a friend. ALL of them have duff switches.
Most cable probs are intermittent and where the cable goes into the tool.

 

[Jim Davey]

Check the cable, they tend to break at the point where they enter the machine due to fatigue. I take the cable off and pull firmly on the individual wires to be sure, if they are broken they will pull out very easily, especially if the insulation is rubber and not PVC. A continuity test with a meter often is inconclusive as only the tiniest strand of wire needs to be touching and the meter will buzz and give you an indication of continuity. I've had hundreds of power tools through the shop with nothing more than cable breaks so it's always the first thing I check.

 

[wristpin]

Cable faults are usually within a foot or so of the tool and you can sometimes see heat discolouration on the outer insulation.

 

[AndyStobbs]

Had a sander fail once, it was basically an angle grinder, with a inductor in circuit to limit the speed. The inductor failed on the one I had, tried to bypass it which restored the sander, but it ran way too fast. Don't think I ever did get around to slowing it back down with a resistance in circuit.

 

[ford34/2]

Sander

If its a half descent and cost a few bob Sander I would second the Cable opinion, a regular common fault, and sometimes a nuisance to trace as it can be intermittent. A meter will soon check continuity, or disconnect and pull the inner cables with a pair of pliers, one cable at a time and it will probably pull out of the sheathing. The vibration near to the handle fractures the cable.

Stan

 

[brokenbiker]

cable and switch would be my first port of call. forget belling them out with a meter, as said above it means nothing if one single strand is touching, or if you have the cable resting I the right position, it may break again as soon as you move it.

if you bypass the switch, make sure it is unplugged when you do it, and make sure there is no disc in it when you pug it in. switch it on, if it runs switch it off and get a new switch

 

[Wedg1e]

240v? Could be a broken motor winding. I've seen it happen a few times on power tools and especially with orbital sanders: what happens is that the user slaps the pad with his hand to clear the clogging then presses the start button and nothing happens. The hot motor winding snaps with the impact. Can also happen to dropped drills.
110V tools don't suffer from it as their motors are wound with a heavier gauge of wire.

 

[plantlife]

Hi everyone, thanks for all the helpful replies.

It is a Mac Allister 450 w sander. It was expensive when I first bought it. Not sure if its any good, but its sanded loads of stuff for me.

I've always stayed away from electrics/fixing "broken" power tools. Never again will i bin an item that gives me symtons of been broke!

As some of you have recommended, I started with the switch. As the cable looked ok, If the switch was ok. I was going to remove a section of wire to make sure.

I stuck the voltmeter on the switch. Bingo! Check both on/off positions....nothing on the voltmeter! I decided to clean the connectors on the switch, as I haven't got a spare one. Connected it back up, and it showed voltage on the meter. I tried it and it worked.
I don't know if you get connectors/spades that get grotty once in a while and stop working?? But, I'm going to have a look on the bay to see if there's any switches, and buy a few in, just incase it goes again.

I've looked at my grinder too, I'm dubious about putting my voltmeter on it, even inside the machine all the power cables look huge and dangerous. lol.

Thanks again for all your help.

 

[AndyStobbs]

A 450w sander will give you just the same shock as a 2kw grinder. 240v is 240v, touch the wrong bit and you'll know it.

 

[ford34/2]

result

any tool that generates dust gets in a right mess after a few years. Belt sanders, grinders, orbital etc etc,You cant believe how the stuff penetrates into sealed switches etc, glad you found it.
Many of the local power tool repair lads might find you a compatible switch that might fit should you get stuck.( Lords, TyneTees, CMC) possibly even Hilti)

Stan

 

[PTvor]

I've looked at my grinder too, I'm dubious about putting my voltmeter on it, even inside the machine all the power cables look huge and dangerous. lol.

Thanks again for all your help.

Most digital meters have a continuity buzzer facility. This might be a safer alternative to testing mains voltage.

It's always worth having a look inside power tools which are acting up, and cleaning them out. A lot of problems are down to simple things like dust, stuck brushes or loose connections.

Some modern power tools have brushes which break contact after they are worn past a point. It stops you using them until they are really worn out and damage the commutator but a casual look might suggest the brushes still have some life in them and so can't be the problem.

I had a problem with an SDS drill which would only start when it was tapped, and later not at all. The commutator was covered in a varnishy black deposit. After it was cleaned with a cotton bud and some alcohol it was fine.

 

[brightspark]

A 450w sander will give you just the same shock as a 2kw grinder. 240v is 240v, touch the wrong bit and you'll know it.

that all depends on how dry your skin is and what u are standing on as well as what u touch . its the amperage that kills u not the voltage damp skin = good current flow

 

[PTvor]

that all depends on how dry your skin is and what u are standing on as well as what u touch . its the amperage that kills u not the voltage damp skin = good current flow

Current flow across the heart in particular. Hand to hand or left hand to right foot being particularly dangerous.

 

[AndyStobbs]

that all depends on how dry your skin is and what u are standing on as well as what u touch . its the amperage that kills u not the voltage damp skin = good current flow

I was just making the point that a little machine is no less dangerous than a big one.

 

[plantlife]

This is part of the reason why I've stayed away from electrics. My inexperience could lead to me killing myself.
I try and research as much as possible before touching anything.

 

[Robotstar5]

Try to do as much testing as possible with the mains disconnected using continuity/buzzer on the meter.
A good investment is a set of test leads with various probes, clips etc. example probably find them cheaper on fleabay, amazon etc. these allow you to connect meter and have hands clear when applying mains voltage.
If possible, keep one hand in pocket which will prevent "cross body" shock

 

[plantlife]

Try to do as much testing as possible with the mains disconnected using continuity/buzzer on the meter.
A good investment is a set of test leads with various probes, clips etc. example probably find them cheaper on fleabay, amazon etc. these allow you to connect meter and have hands clear when applying mains voltage.
If possible, keep one hand in pocket which will prevent "cross body" shock

Hi,

Thanks for the tip, will look into the clips/probes. I think its wiser having those.
atb
Andy