Why do carbon brushes need replacing and what are they?

[Nealcrenshaw]

I notice that a rotary hammer i'm looking at mentioned that it comes with a extra set of carbon brushes,i'm assuming that it has something to do with the motor,but not sure,and how do you replace them?

 

[krusty the clown]

the bruses are what connects the electical power to the armature. there are a soft material so the commutator doesn't wear, so they do. they need to be replaced after a while.

 

[gotmud13613]

I notice that a rotary hammer i'm looking at mentioned that it comes with a extra set of carbon brushes,i'm assuming that it has something to do with the motor,but not sure,and how do you replace them?

Must be a HF tool, All of mine have also came with extra brushes. I check mine maybe once a year but I haven't had any that needed replacement yet (some are getting close though) there grinders seem to use them up more than any other tool.

Here is a pick of the rotary hammer I think you have and I put an arrow where the brushes go (should be one on each side)

 

[russlaferrera]

When you turn the machine on you will see sparks . This is where the brushes meet the armature. On both sides of the motor you should see round plastic disks with screwdriver slots, under these are the brushes.

 

[bchee]

Who else besides HF provides replacement brushes?

I had a HF grinder with extra brushes and thought it was a neat feature, but then I thought maybe it's a sign of lower quality...

I don't have a lot of power tools but I can't recall other manufacturers that provide brushes

 

[dreaminbimmers]

Carbon Brushes...They come in various shapes and sizes.

 

[dreaminbimmers]

Dooh! Picture is too big.

 

[dreaminbimmers]

Some start out dished, others get that way with use.

 

[Elroy]

Helwig Carbon is an old line brush manufacturer. Elroy tenders this link for additional technical information on a subject that appears simple on the surface but has been the subject of extensive research and development:

http://www.helwigcarbon.com/technical/faq.aspx