Launch Slideshow

Makita OMT Teardown

Makita OMT Teardown

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    This is the TM3000C, one of two OMTs (the other is cordless) Makita introduced this spring.
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    Remove screw from rear of tool.
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    Pull housing off to expose the brushes.
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    A spring-loaded clip holds the brush against the commutator on the armature or “rotor”. This is one of two brushes – the other is on the opposite side.
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    Release brush by moving clip off to the side.
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    Pull brush out so it won’t be damaged when you remove the armature.
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    Remove the plastic housing (Makita calls it the head cover) from the front of the tool.
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    Remove the screws that hold the crank housing in place.
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    Pull the crank housing and armature assembly out of the tool.
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    Pull the crank housing off the end of the armature. It’s a tight press fit where the bushing goes in.
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    This is the armature assembly. Electricity flows through a pair of brushes that ride against the commutator – which transfers power to the windings. Brushes are necessary because the armature spins so you can’t hard-wire the connection.
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    The armature assembly is on the left and the crank housing is on the right. The end of the armature shaft is machined off-center so when the motor spins the drive bearing moves eccentrically – causing it to press one way and then the other against a pair of arms. The arms are connected to the spindle. When the arms move from side-to-side, the spindle does too - one oscillation for each revolution of the motor.

I was working on a story about oscillating multi-tools (OMTs) when it occurred to me I had no idea how a spinning motor could make a spindle go from side-to-side. So I did what I always do when a tool confuses me – I tore it apart.

I went with a Makita OMT because it looked like it would be easier to take apart than some of the other models. And as OMTs go, it's not very expensive ($160) so it wouldn't be the end of the world if it didn't work after I put it back together.

Click on the slideshow above for images of the tool being taken apart (there are 12 photos in all).

By the way – I put the OMT back together and it works just fine (though Makita might argue with the type of grease I used to re-lube the spindle mechanism).

Archived Comment

September 18, 2012

Would it be akin to cannibalism to have used a Makita instead of a DeWALT to take apart the OMT? :-)

Posted By: MT Vessel | Time: 5:48:34.313 PM