Hi, I’m Mark from eReplacementParts.com.
In this video, I’m going to show you how to replace the front armature bearing O-ring
on a Makita Grinder. The front armature bearing O-ring forms a seal between the front armature
bearing and the grease portion of the gearbox. It’s possible that the O-ring can go bad
and allow some oil or grease to leak into the armature area. If this occurs, you’ll
want to replace this O-ring. Replacing, it is easy to do and I’m going to show you
how. O-rings, as well as many other parts, can be found on our website. Let’s get started. I’ll begin by removing the side handle and
the guard. The gearbox housing is held in place with four screws. I’ll go ahead and
remove those. Now I can remove the rear housing. It’s held in place with a single screw.
Now move the brush springs to the side of the brush holder. This will remove the tension
from the brushes so they’re not pressing against the armature. I’ll do this on both
sides. With the tension removed from the brushes, now I can go ahead and remove the armature
assembly. Now remove the drive gear. It’s secured with a nut. Now remove the front armature
bearing and the gear housing cover from the armature. To do that, I’ll place the cover
in the open jaws on my vise. Then using a rubber mallet, I’ll tap the armature shaft
away from the bearing. With the armature removed, now I can remove the bearing from the gear
housing cover. To do that, I’ll again place the cover on the vise jaws, and I’ll use
a socket that has a diameter that’s the same as the inner race diameter on the bearing.
Now, go ahead and tap the bearing away from the cover. With the bearing removed, now I
can go ahead and remove the front bearing O-ring from the cover. I’ll use a pick to
do this. Now I can install the new front bearing O-ring.
Slide it down into the groove inside the cover. Now install the front armature bearing. I’ll
place it into the gear housing cover, and this time use a socket that has a diameter
the same as the outer race on the bearing to tap it into place. Now I can install the
gear housing cover assembly back onto the armature. I’ll seat the bearing back onto
the armature shaft using a socket that has a diameter the same as the diameter on the
inner bearing race. Now I can reinstall the drive gear and secure it with a nut. Now I
can install the armature assembly back into the grinder. I’ll reinstall the gear housing
assembly to the motor assembly and secure it with the four screws. Now, reposition the
brush spring back over the brush. Now I’ll slide the rear cover back over the motor housing
and secure it with the screw. And I’ll finish up by installing the guard and the side handle. And that’s all it takes to replace the front
armature bearing O-ring on a Makita Grinder. If you found this video helpful, be sure to
give us a thumbs-up. And leave a comment.