Worn Armature Gear on Miter Saw

[Patrick Varley]

So I recently picked up a sliding compund miter saw for next to nothing at an auction. Spun up but sounded a little rough, but figured I could get it home and at worst it might need some new bearings and brushes. As it turns out after I took it apart I found that the teeth on the armature gear had been worn significantly in the middle (see picture). This causes then to only make slight contact with the arbor drive gear. The reason it was sounding rough is the the gears were slipping/grinding significantly when it runs. I can replace the armature assembly for about $50, but my question is: Is there something I should look for that caused this to happen in the first place? In other words, if I replace the armature, am I going to be back in the same situation a year from now? Everything else looks like it's in good shape, and the arbor bearing/gear spin freely on their own.

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[Cary Falk]

What does the gear that connects to this look like? I would go through everything and make sure everything else moves freely and relube. New bearings all around would not be a bad idea since you have it in pieces. Depends on the brand if I would cut my losses or continue.

[Frank Pratt]

What he said. And be sure to thoroughly clean out the gearbox. That's a lot of metal that floating around in there.

[Patrick Varley]

Thanks Cary and Frank. The drive gear looks ok, and doesn't show any spots of uneven wear. There was in fact a bunch of metal shavings in the gearbox when I cleaned it out, which was my first hint there was something more problematic going on.
Ultimately it's a $200 Craftsman saw that I would be into about $70 if I replace the armature ($20 for the saw $50 for the part). I was going to give it to a friend who needs it for general homeowner type stuff, and I figured it's still probably worth it as even the cheapest Harbor Freight slider is $120 without coupon, and this is still a better saw (even if only by a smaller margin).

[michael langman]

Something definitely caused that. Too much damage to not happen on it's own.
A misalignment of some kind happening some how seems likely.
I would think the mating part would be damaged also. May not be as noticeable.

[Ken Combs]

How was the lubricant in the gearbox? I'll bet the root cause was dry and/or insufficient grease. If you fix it, be sure to fill it well with the recommended product.