Issue with sander motor

Stephen Newell · Dec 14, 2014

I have two porter cable random orbital sanders which when sanding the RPM drops a lot and have to stop and allow the speed to pick up and I'm not putting too much pressure on the sander. The longer I work with it the harder time it has to recover the speed. I attempted a fix and bought new brushes for it and took it apart and cleaned the commutator and the sander works good for a couple of days and then does the same thing. There isn't excessive wear on the commutator however as long as I take the sander apart every day or so and clean the commutator the sander will work fine. Is there any fix for a sander like this other than replacing the armature.

Russ from MN · Dec 14, 2014

Did you try oiling the bearings?

JD Seller · Dec 14, 2014

Russ has the only idea I could think of.

The armature maybe worn to where it is wearing out fast. If the "dust" fills the spaces between the armature windings then they "short" the brush contact surface out.

The trouble is that Porter cable stuff is kind of a lower end product. I have found their stuff is usually lower in torque and power than other "better" brands.

guido · Dec 14, 2014

Hello Stephen Newell,

I'm not familiar with the brush set-up on that model. One thing you can try if you can. Increase brush spring pressure. This will do two things:
It will lower the motor's R.P.M.'s but it will increase the torque. Also make sure the edges of the brushes, leading edge more important then the trailing edge, Have no sharp edges. This will make then catch the armature segments, which will make them bounce and slow the motor down. Let me know how you make out.......

Guido.

Issue with sander motor

Stephen Newell

Well-known Member

Russ from MN

Well-known Member

JD Seller

Well-known Member

guido

Well-known Member

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