Question regarding installing armature bearing Bosch 4000

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Forum topic by savan posted 07-25-2013 03:59 PM 2275 views 0 times favorited 4 replies Add to Favorites Watch
View savan's profile


97 posts in 2419 days

07-25-2013 03:59 PM

I’m replacing the armature bearing on a Bosch 4000. Is this a safe way to press on the bearing?

I plan on:
-putting the new bearing on the armature
-holding a socket on the bearing
-holding that assembly in my Rockwell Jawhorse
-using the Jawhorse as a press

My question is, is the shaft of the armature all one piece? I’m I going to mess anything up by compressing the whole shaft vs trying to grip somewhere else on the body of the armature and pressing the bearing?


I caught this saw on CL for $50 and the guy threw in the red folding stand. He said “the motor is shot” and that he took it to acme tools and they told him it’d be near $300 to fix it. Everything else is working fine but the motor started to throw sparks. I figured $50 was worth the gamble.

I picked up the saw and the motor was in a cardboard box :P

After some poking around I saw that the bearing was toast, so much so that it had melted the area of the motor housing that the bearing rests in. The rest of the armature didn’t look burnt or anything. The brushes looked ok

I ordered a new motor housing ($25) and bearing ($3) parts get here today so wish me luck! I might’ve gotten a great (2nd) saw for a song!

4 replies so far

View waho6o9's profile


8207 posts in 2604 days

#1 posted 07-25-2013 04:15 PM

It appears to be a sound plan you have there, I’d go for it.

Congrats on a second saw.

View exelectrician's profile


2327 posts in 2455 days

#2 posted 07-25-2013 05:26 PM

You are on the right track, post the good news when the new baby is up and running!

-- Love thy neighbour as thyself

View savan's profile


97 posts in 2419 days

#3 posted 07-27-2013 02:49 AM

Ok, I got the motor all put back together in the new housing with the new bearing.

I fired it up and I was reminded of the fourth of july. I tried a couple replacement brushes from my mitre saw and they got chewed up in a spark filled light show.

I looked again at the armature and the commutator looks damaged. Scored and pitted. Before replacing it I’m thinking of chucking it up in a drill and filing it down just enough to remove the scratches and pits. Then smoothing it out w/ 400 or 800 grit.

Any thoughts on this idea?

View waho6o9's profile


8207 posts in 2604 days

#4 posted 07-27-2013 03:02 AM

I’d speak with Bosch tech support and see what they have to say.

They were very helpful and knowledgeable when I replaced some things
on my motor.

No sense in doing more damage than necessary.

Good luck now.

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