It can be checked by rotating the shaft with out any load if it is
stiff or has lots play they are worn. Also you can tell by excessive
heat at the bushing sites. If brushes are going bad the motor will fail under heavy load and the smell of electrical parts burning is another way to tell. Also heavy sparking at the brush site will also reveal a problem with the brushes. Constant blowing of fuses under load will also indicate a problem with brushes. The main thing is it will not perform as it used to it will be much weaker or not work at all.
stiff or has lots play they are worn. Also you can tell by excessive
heat at the bushing sites. If brushes are going bad the motor will fail under heavy load and the smell of electrical parts burning is another way to tell. Also heavy sparking at the brush site will also reveal a problem with the brushes. Constant blowing of fuses under load will also indicate a problem with brushes. The main thing is it will not perform as it used to it will be much weaker or not work at all.