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During my early larnin' period, we were taught not to undercut the
commutators on starters, only on generators. One is actually not
cleaning between segments or bars by doing this, but rather undercutting
the insulation between the bars to allow the brushes to run
smoothly. Starter commutators were turned or sanded (literally, with flint sandpaper) smooth rather than undercut. The theory was that undercutting allowed arcing under high current conditions found in starters but not in generators. By having a smooth commutator with the bars and insulation at the same level arcing was greatly reduced if not eliminated. Starters usually turn thousands of fewer rpms than generators which is why the smooth commutator takes years to wear lower than the insulation. I have seen undercut starters that have erosion on the downstream side of the bars. With regard to brush stones, I have used them in power generation with large generators, but in automotive use, I find that a strip of flint sandpaper wrapped face up around the commutator works as well with little or no residue to find it's way into bushings. Just lower the brushes and turn the generator/starter by hand a few revolutions and the brushes should be pretty much seated. With a gear reduction starter you may have to turn the rotor by hand with the front cap off due to the gear reduction. If you try this method don't use emery clothe or any other conductive abrasive. Bill Huff At 7/3/200701:09 PM, John McCann wrote: I think the stock starter has what it takes to start your engine, parts are available at Rock Auto, be sure to clean between the commutator segments if you do it yourself, I use a hacksaw blade broken off and ground to a point on the teeth side to drag between the segments to remove any conductive material. When you tighten the brushes, be sure they remain flat on the commutator, brush seating stones are available to speed the seating of the brushes ************************************************************* To unsubscribe or set your subscription options,
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