Makita OMT Teardown

This is the TM3000C, one of two OMTs (the other is cordless) Makita introduced this spring.

Remove screw from rear of tool.

Pull housing off to expose the brushes.

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.

Release brush by moving clip off to the side.

Pull brush out so it won’t be damaged when you remove the armature.

Remove the plastic housing (Makita calls it the head cover) from the front of the tool.

Remove the screws that hold the crank housing in place.

Pull the crank housing and armature assembly out of the tool.

Pull the crank housing off the end of the armature. It’s a tight press fit where the bushing goes in.

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.

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.

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