Orbital sander not working - brushes?

[phatboy]

Hi all,

I have this vintage B&D sander, which has been passed through 3 generations!



It's a Black & Decker KA185.

In the past few days, it's got very very noisy, and seems to not really vibrate the plate.

I opened it up, but cannot really see if the brushes need replacing or not, they are well hidden so cannot see wear, nor push them back from the armature. Also, I haven't a clue how I would replace them..... is it a drop the motor job, and then push in new brushes? If that's even the fault....



Thanks
Tim

 

[Ryler]

Perhaps its time for permanent retirement.

 

[phatboy]

Perhaps its time for permanent retirement.

Oh... I thought the aim was to repair where possible? So are you saying it's probably not brushes, as that would be a cheap fix....

 

[Ryler]

Have thrown things like that in the bin tbh.
Could be the switch or a broken lead.

 

[Burnerman]

The brushes are visible in your second pic and they look OK from here.
What you need to look out for are a reduction in speed, excess sparking and a burning smell from the motor.
Any of these and its game over, I’m afraid.
John

 

[foxhole]

If it runs but does not vibrate chances are gearing has worn out .

 

[mattylad]

BTW, you called it an "Orbital sander" - it's not orbital

 

[conny]

If you have a multi meter test your cable for continuity of all leads and the fuse in the plug. You will need to operate the switch to check the live side, (and possibly the neutral if it is a double pole switch). If this is ok then do the following.

Those brush boxes have a small metal tab across the end. You need to lift the tab away to allow the brushes to 'spring' out. The brush lead will be soldered to the metal tab so they will not fly out across the floor.
Although they look in good condition they may be jammed in the box through an accumulation of carbon dust and damp. It appears they are touching the commutator but, if they are jammed in the box, there may well be a very small gap meaning they are not making contact.
I would tackle those brushes first before dumping it. If you manage to get them out give them a VERY LIGHT rub along the sides and edges with fine glasspaper, (do NOT use emery cloth or any abrasive with metal particles!). Whilst they are out of the box rub a small bottle brush through the boxes to clear any carbon off the insides of the box.
With the brushes out slide a sliver of glasspaper under the boxes and around the comm so it forms a loop. Hold both ends of the loop in between finger and thumb of one hand and rotate the armature shaft with the other hand. You are aiming the clean up the comm segments so they look shiny enabling a good contact with the brushes when re-fitted.
Gently brush away any dust into a vacuum cleaner nozzle rather than blowing it away. If it gets in your throat it gives you a horrible taste for hours.

Let us know if you get it working.

 

[mattylad]

FWIW I too have one of those, its been kicking around for the past 30 years, it's useless and I need to throw it away - a little palm sander (shaped like an iron) that I got from Argos has been far better.

 

[phatboy]

If you have a multi meter test your cable for continuity of all leads and the fuse in the plug. You will need to operate the switch to check the live side, (and possibly the neutral if it is a double pole switch). If this is ok then do the following.

Those brush boxes have a small metal tab across the end. You need to lift the tab away to allow the brushes to 'spring' out. The brush lead will be soldered to the metal tab so they will not fly out across the floor.
Although they look in good condition they may be jammed in the box through an accumulation of carbon dust and damp. It appears they are touching the commutator but, if they are jammed in the box, there may well be a very small gap meaning they are not making contact.
I would tackle those brushes first before dumping it. If you manage to get them out give them a VERY LIGHT rub along the sides and edges with fine glasspaper, (do NOT use emery cloth or any abrasive with metal particles!). Whilst they are out of the box rub a small bottle brush through the boxes to clear any carbon off the insides of the box.
With the brushes out slide a sliver of glasspaper under the boxes and around the comm so it forms a loop. Hold both ends of the loop in between finger and thumb of one hand and rotate the armature shaft with the other hand. You are aiming the clean up the comm segments so they look shiny enabling a good contact with the brushes when re-fitted.
Gently brush away any dust into a vacuum cleaner nozzle rather than blowing it away. If it gets in your throat it gives you a horrible taste for hours.

Let us know if you get it working.

I shall certainly give it a go! First issue is nowhere local seems to know what 'glass paper' even is... I cannot say I've seen it for years.

Is Wet and Dry paper for automotive sanding metal free do you know? I have loads of that in very fine grades.

Thanks for the comprehensive guide.... I want to repair this in part just because I want to see if I can do it.

 

[phatboy]

FWIW I too have one of those, its been kicking around for the past 30 years, it's useless and I need to throw it away - a little palm sander (shaped like an iron) that I got from Argos has been far better.

Really? I found it to be pretty good until the other week, maybe I just don't know what I'm missing?

 

[Burnerman]

Wet and dry will be fine although it does contain carborundum so do wash the segments out afterwards.
John

 

[phatboy]

Wet and dry will be fine although it does contain carborundum so do wash the segments out afterwards.
John

Thanks, just a wet cotton bud with water or similar? Or white spirit? I've never done this kind of repair before!

 

[JohnD]

Is Wet and Dry paper for automotive sanding metal free do you know?

yes, it's carborundum particles (hence black)

edit
too slow

 

[phatboy]

Thanks all,

Gave it a good clean. I could only get the right brush out, the power switch blocks getting the other out. But I managed to shift everything a little and at least clean the brush end on that side, but not inside the housing. Lots of deposits came off, and the comm is now nicely polished.

It might be a tiny bit better, but still performance isn't great and its bloody noisy!

Do I need to really find a way to get both brushes completely out? Can I try anything else? Or is it tool heaven?

Thanks
Tim