Replies

1. 
   RalphBarker | Mar 17, 2010 02:58am | #1

   Sounds like you may have some debris in there, perhaps metalic, that is grinding against the brushes. Whether you can disassemble the motor sufficiently to do an inspection is another matter, of course. You might want to contact Makita customer support about the problem.

2. 
   KeithNewton | Mar 17, 2010 11:03am | #2

   A bad bearing in that end of the motor could explain noise and arcing.  A loose plate in the commutator will really eat brushes. 

   Lots of arcing will sometimes cause some pitting between the plates of the commutator. You can either take it out and turn it true on a lathe, or get some temporary dressing by holding a friable honing stick against it while the motor runs, if there is a hole to stick it in. i think it is called a Tommy-stick. 

1. 
   davcefai | Mar 18, 2010 03:37pm | #3

   Dangerous

   "holding a friable honing stick against it while the motor runs,"

   Isn't that rather dangerous? Holding a honing stick against a live spinning commutator? Granted that the plates being touched are not, at that moment, live, one little slip........

3. 
   Jobenus | Mar 20, 2010 08:08pm | #4

   Replacing the Bearings

   Rould replacing the bearings be an option and if so any advice on how to do this?

1. 
   wotnow | Mar 20, 2010 10:42pm | #5

   All of the above can cause what you are experiencing. If you are gojng to the trouble of replacing the bearing, it would be advisable to put the armature on a lathe and skim the copper segments to give a new surface for the brushes. The commutater will be pitted, scored and burnt which will add to your woes. Make sure you don't skim the commutator too much as you will have to undercut the insulation between the segments. On the whole it may be cheaper to replace the armture.

   wot

2. 
   wotnow | Mar 20, 2010 10:52pm | #6

   Re Replacing the Bearings

   Job

   Remove the brushes first.

   You should find some long screws that hold the motor casing together longitudinally. Remove these and you should be able to split the casing in two pieces.

   With some luck one of the bearings will stay in the housing and you will be able to remove the armature. Take care you don't destroy any of the field windings in the casing.

   The bearings will either punch out of the casing or need to be pulled with bearing pullers. When replacing bearings, make sure you use a swage that fits over the shaft and only mates with the inner part of the bearring when driving it back into place.

   Good luck

   wot