What goes bad in a brushed motor?

[xlowxyotax88x]

So I have been replacing deck boards and railings on a porch at home and with only about 15 or so cuts left my miter saw craps out. Now it's an older craftsman 10 inch saw not sure of date but I'd say no more than 20 years if that, but hasn't had a ton of use. It was given to me by an inlaw that was moving away and I've only cut a handful of boards with it up until this project which isn't major by any means. I was cutting a 2x4 and it seemed weak and about that time the motor stopped and started smoking, I unplugged it, the blade turns no problem, pulled the brushes and they look good, and spun the blade again and can see the motor turning. Just curious what else goes bad?

 

[seber]

Usually it is brushes or switch, but smoke means bearing or coil. Coil could be feild or arbor. I'd bet on a bad bearing. Sitting for years will do that. I just repaired a Milwaukee impact that had a bad 1/4" bearing at the rear. Locked it up solid.

 

[FMB4]

Brushes, switch, and then commutator are often the culprits.

 

[RTM]

Older Craftsman always had bad bearings as a failure point, not sure about 20 year old. My CMan saw is 20 ish now with very irregular usage, so if it was full of dust and debris from laying about would not surprise me. Not sure if enough to smoke things tho.

 

[metaldad]

i've never ever had to change brushes on a corded tool.
i have alot of them.
i use them alot.
for 40+ years
and i repair when the parts are still available
let the magic smoke out? most likely a winding

 

[xlowxyotax88x]

Guess I'm in the market for a cheap saw lol. As little as it ever gets used I'll most likely just get something from harbor freight, unless something like craftsman or Ryobi is close to their prices

 

[Badgerstate]

Typically the brushes just go bad. They are replaceable. If you dont use it much, Id find it difficult to believe that the brushes are worn out though. It is possible that you have corrosion on the brushes from it sitting all of the time.

 

[Firebrick43]

Brushes in high use items, bearings in old motors. Grease oxidizes and get to thick to lubricate sufficiently

 

[The Cobbler]

shorted armature or field is my guess