Makita belt sander rebuild


  #1  
Old 01-13-23, 10:27 AM
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Makita belt sander rebuild

Have a Makita belt sander model # 9924DB. Seized. Friend asked me to check it out. The bearings have disintegrated. This is on the right side. Iím sure the same has happened on the opposite side.

Two questions. It appears the bearing has seized onto the shaft. Any suggestions on how to remove it with out damaging other parts. Also, if any of you would be willing to look at the parts list (Makita Belt Sander | 9924DB | eReplacementParts.com) I canít seem to figure out where items 17 and 18 (rubber pins) fit into the assembly. They have obviously disintegrated also. I suspect they are just cushions to hold the cover plates steady.

And last but not least do you think itís worth repairing? My friend thinks itís about 40 to 50 years old. But I have my doubts about that. It was his Dads.



Bearings lost

Debris removed from bearing housing.

Ditto


I got to say, they don't build them like this anymore. Mostly metal parts and no snap together plastic. Nice long cord.
 
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Old 01-13-23, 03:03 PM
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The bearing in the photo is on the motor's rotor shaft (#14). I think it is easier to remove/replace the bearing with the rotor removed. The other end of the rotor shaft must be accessed. This is a universal motor so there are brushes (#6) that have to be removed along with a belt pulley (#4) before the rotor can be removed. Not knowing how tight the bearing is on the shaft, I would try a 2 jaw faucet handle puller first. If that doesn't work, you will have to get something stronger but the jaws need to fit below the bearing. I think it is worth fixing assuming the motor is OK. My guess items 17 and 18 hold the stator (#10) from moving in the housing (#5).
 
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Old 01-13-23, 05:00 PM
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"My guess items 17 and 18 hold the stator (#10) from moving in the housing (#5)."
​​​​​​​

Yes, now that you say it, that makes sense. In fact, they may very well still be in there.

What worries me, will the shaft be score beyond use if the bearing has been "galled" to it. Not sure galling would be the right term. But it seems the bearing should just slip in the shaft. Or would the bearing be a press fit with the inner race being the wear surface? Now that I think about it that may be the proper assembly. But I never remember seeing a ball bearing race press fit to a shaft.

Looks like this belt sander goes for around $300. So, I guess it's worth it.

I'll need to do a cost comparison between all possible parts that might be replaced vs cost of a new unit. I think I'll include the cost of the Armature assembly which includes the bearings installed and the rear fan attached for $161.00. And a set of new brushes at $7.70 each.

Approximately just under $200 to rebuild vs $300 (or maybe less).

Not so attractive to rebuild now!

I'll advise my friend and let him decide.
 
  #4  
Old 01-14-23, 06:13 AM
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A ball bearing's inner and outer race must be stationary, relative to their mounting surface, so only the balls are creating friction. Hence both the outer and inner races need to be a press fit with the mounting surfaces. The bearings (#12 and #16) can be pulled off the shaft without damaging shaft. Bearing's position on the shaft, relative to the commutator, should be measured before removal so new bearing installation location positions commutator in line with brush holders. I would replace with sealed bearings if available. Noticed part #21 is not listed in parts list. Do you have any other literature that may identify it? My guess is it is a thermal fuse.
 
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Old 01-14-23, 06:31 AM
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I have looked a several different on-line parts list and they all show part #21 but do not list it or identify it.
I did however find this:
21
Makita

NOISE SUPPRESSOR / DA3000R / 9032 - 645209-3

 
 

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