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Question about miter saw motor repair

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Forum topic by kenthepainter posted 09-26-2016 01:41 PM 185 views 0 times favorited 4 replies Add to Favorites Watch
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kenthepainter

2 posts in 1403 days


09-26-2016 01:41 PM

I just bought a used Hitachi C8FB miter saw and have started taking it apart to tune it up, new bearings , brushes, cleaning , adjustments etc. The question I have is about the commutator on the motor shaft, it had a concave wear pattern. Has anyone found this before and does anyone know what this is an indicator of ?


4 replies so far

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Bill White

4452 posts in 3424 days


#1 posted 09-26-2016 03:26 PM

Long term use. The brushes wear the commutator. It should be trued or the new brushes (if needed) won’t seat properly.
Bill

-- bill@magraphics.us

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splintergroup

828 posts in 685 days


#2 posted 09-26-2016 05:21 PM

Bill nailed it.

Some motor shops will re-turn the commutator on a lathe to restore the surface, but only if the motor is built for that kind of reconditioning.

A new part isn’t cheap, but at least they are available.

Edit: Just saw it on Amazon for a tad cheaper

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kenthepainter

2 posts in 1403 days


#3 posted 09-26-2016 05:37 PM

I chucked it up in my drill press and ran a file on it to smooth it out. Then I cleaned out the groves. I’ll spray it down with contact cleaner, new brushes are on the way. I was gonna take to be turned but decided to try the file & drill press. If that doesn’t work I might buy a new armature, not sure if it will be worth it though, I found one for $125.00, I’ve got $165.00 in it so far I might just cut my losses before buying a new armature. A 10 inch Ryobi slider is under $200.00 which would suit my needs. The main reason for my impulse purchase was because of the good reputation this saw has

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splintergroup

828 posts in 685 days


#4 posted 09-26-2016 05:54 PM

I’ve done the file and drill press trick before and it can work in a pinch.
One thing you want to do is drill a bearing sized hole in a piece of wood and use this, clamped to the DP table, to support the lower end of the armature while you file it.

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