Grinder gone on strike....

[slim_boy_fat]

One of my grinders stopped working today while I was cutting some thin metal with a 1mm disc. Slowed down, then picked up speed again, slowed down...

I turned it off and on again [works with computers ] and it spun up then stopped altogether.

I'm thinking motor brushes but didn't have time to investigate today. Any other likely cause before I start pulling things apart?

 

[Red'n'Black]

What make / model is it? I have an old Elu 4 1/2" that did that. When I stripped it down there was some sort of electronic soft-start module that had died, all potted up so not repairable. Motor was only 700W so it seemed a bit unnecessary to me, wired the switch direct to the motor and it's been fine ever since.

[EDIT] I wouldn't advise doing this on a 9" or bigger grinder though, it's likely to blow fuses and/or jump out of your hand on startup without it. I also have a B&D Pro 9" and that scares me enough as it is

 

[slim_boy_fat]

What make / model is it? I have an old Elu 4 1/2" that did that. When I stripped it down there was some sort of electronic soft-start module that had died, all potted up so not repairable. Motor was only 700W so it seemed a bit unnecessary to me, wired the switch direct to the motor and it's been fine ever since.

Can't remember the brand, I bought it online from somewhere like UKhomeshopping [?] so will have to check tomorrow. I don't think it has the soft-start function , engage the switch and it spins up to full speed sharpish...or it used to. 900W iirc.

 

[zzr1200]

It could be burnt out bushes or commutator, if its a decent make you might be able to replace the bushes and clean the common.

If its a cheapy grinder bin it and buy a Metabo.

 

[slim_boy_fat]

It could be burnt out bushes or commutator, if its a decent make you might be able to replace the bushes and clean the common.

If its a cheapy grinder bin it and buy a Metabo.

I'm hoping it's an easy fix, it's one of 4 I have and oddly enough one of the others needs a new shaft bearing so is out of commission atm. I only have them due to laziness, I could live with one and just change discs etc as needed.......

 

[gaz1]

[EDIT] I wouldn't advise doing this on a 9" or bigger grinder though, it's likely to blow fuses and/or jump out of your hand on startup without it. I also have a B&D Pro 9" and that scares me enough as it is

my 9" grinder has no soft start and on start up it twists (kick) you get used to it but i prefer it this way soft start nah i dont like them they can slow down during use unlike ones where power is there all the time

 

[slim_boy_fat]

It lives!! Just needed brush replacement, had a look at the comm and it looks OK. But....only one brush was down to the limit with the other barely worn? Why would that be? I've only replaced the one atm as I only had 2 spares, and as sure as a cat's a hairy beast another grinder will throw a hissy fit in sympathy.

Are brushes for these things universal, before I order more from the 'Bay of Everything?

 

[zzr1200]

I doubt if if they all use the same bushes, more like to be all different specs...

 

[slim_boy_fat]

I doubt if if they all use the same bushes, more like to be all different specs...

I did wonder about that, but both grinders are 900W and the brushes looked identical and fitted perfectly.

 

[123hotchef]

well it works that is all that matters!

 

[Red'n'Black]

It lives!! Just needed brush replacement, had a look at the comm and it looks OK. But....only one brush was down to the limit with the other barely worn? Why would that be?

Good stuff, glad you got it sorted.

Uneven pressure is the usual cause of them wearing at a different rate, check for a build up of crud in the holder and / or weak spring, if that's not part of the replacement.

 

[slim_boy_fat]

Uneven pressure is the usual cause of them wearing at a different rate

Probably my own fault then, I have to do a lot of looking sideways due to eye problem(s).

 

[anto44]

Are brushes for these things universal, before I order more from the 'Bay of Everything?

From what I've seen no not really universal. I had to get brushes for a makita a while back and although getting replacements was no problem I had to remove the old ones and bring them to the shop to be sure i was getting the right ones.
The sticker with model number was missing off the grinder and he had over a dozen different brushes for makitas. If I'd had the model no. he could've picked them from the book though.

 

[Turbo]

I think my grinder has joined your picket line as it has gone on strike too!

I was using my trusty 5" parkside grinder tonight with a wire cup brush to clean up rusty steel & a funny noise started coming from the gearbox. Hopefully it's just a bearing, I'll take a look tomorrow. It's no shame if it's terminal, the grinder has been worked hard with either a grinding disc or mostly a knotted wire wheel on it and they are hard on any grinder.

BTW there are many different carbon brushes for grinders out there. They commonly are listed according to their dimensions ie length, width & breadth plus what type of wiring connection they have. If you can't get an exact match get a slightly larger one and use sandpaper or a file to get them to fit, they are quite soft!