Thread: My Black & Decker orbital sander making a small spark

Any motor with brushes (Universal motor) will have some arcing between the brushes and the commutator (the copper segments mounted to the motor shaft that the brushs rub against). What matters really is the extent of the arcing, whether it has noticably increased recently, the sound of the motor, and whether there are any 'burning' smells.

Often people become concerned as they work in a darker area than normal and the arcing becomes more obvious due to the darker surrounds. In the absence of the motor sounding distressed or uneven, or burning smells, it should be OK. However if it has done a lot of work, the brushes may be worn and due for replacement. Where abouts in Victoria are you, as we might be able to get someone nearby to take a quick look.

Malb
the motor slows down and if you give it a slight wack it will speed up again.

So you own a bussiness and you what me to bring it in. I live in the Dingley area.

i can take a photo of the sander if that help identifying its age as i don't know its age.

Harrison, I am in Croydon (outer Eastern suburbs). Middle aged with good mechanical and electrical/electronic background, qualified but non practising engineer. Currently working as a parcel post delivery person around the Port Melbourne area. Definitely not touting for business but willing to help someone when needed.

The 'slowing down but restores speed with a wack' scenario wasn't in the the original post, but will most likely be being caused by excessive loading somewhere in the system, possibly caused by sanding dust that has mixed with lube in the mechanism or bearings, loading these compoments and hence the motor. Brush arcing is a function of the motor current draw, which in turn is a function of motor load. The other obvious possibilities are a poor connection from the stationary windings to brush holders, which the wack temporarily improves, or your original guess of worn brushes hanging in the brush holder, again being temporarily improved by the wack.

If you can post a pic of the unit and confirm that it is servicable (i.e the housing is screwed together rather than bonded) I can have a look for you and see what can be done for it. It would be fairly unlikely that it would be viable to have it commercially repaired as labour rates would likely exceed replacement cost.

Mal

ill try and get one up tomorow
Harrison