Hello you guys. What is the minimum diameter a can cut a comm. I have a few extras I want to experiment on getting higher RPM out of. Thanks in advance.:dude:

Hello you guys. What is the minimum diameter a can cut a comm. I have a few extras I want to experiment on getting higher RPM out of. Thanks in advance.:dude:

There isn't a stated minimum dia for a commutator. There is either a good cut or I screw up a cut and the comm drops off in the lathe bad. Don't look for unrealized RPM in the comm it ain't there!
A Good comm cut restores the original power to the motor by resurfacing the brush path. This make the brushes vibrate less as the arm spins which by the way improves the power.
Now you can play with different types of brushes, brush springs, brush hoods, and even a different type of shunt and even applying a conductive compound to the brushes. You can even polish the armature shaft where it contacts the bearing or bushings but at the most you will see a 1K RPM increase.

If you are really looking for more RPM then rewind the arm.

If you're wanting to know what the min. diameter is before the copper comes flying off or the brushes burn through it then .270 is pretty much it.