I am about to refurbish my generator and noticed that the commutator has some wear, but not bad. I plan to put it on my lathe and dress up the commutator with a very fine file. After that I will offset the mica.
Does anyone know how much can be taken off (or worn off) the commutator before it is no longer repairable?
Thank you, Paul in Tacoma
Paul, I would caution against the use of a file to true up the commutator. It should be machined. My auto elec son has a specially sharpened tool for the purpose, which I am forbidden to touch!
The segments will need to be undercut once the machining is done.
Hope this helps.
Allan from down under.
The runout of the commutator is critical, machine it carefully, then undercut. Dave in Bellingham,WA
Paul, take a VERY LIGHT cut!It's not difficult, then after undercutting the mica use a bit of fine wet/dry paper to remove any burrs the undercutting might have created. An armature lathe has a special fitting to do the undercutting; makes the job easy!
Look at the end of the commutator and it sections, as long as they are not down to a nib you should be ok. As David said, take a light cut. No file, it just will follow any out of roundness and amplify it.
If you have a lathe, why would you even consider using a file? The commutator segments are shaped like a bracket "]" so they are thinner than you think. Ron probably has the minimum diameter on the tip of his tongue but I seem to recall 1.5" or similar. Examine the center drilling carefully for rust, debris and trueness to the shaft OD. Many are not true. It's better to mount the bearing and use a cup center on the bearing to cut the commutator. If it's not concentric the brushes will bounce and output drops considerably.