Piston Ring Filer Manual Tool. Engine Piston Ring Filer. 1x Manual Piston Ring Filer Tool. When grinding the product, with the flat side of the piston ring facing down (must), manually turn the rocker to make it grind toward the inner side of the piston, because the grinding wheel will grind toward the outer side of the ring, which is not what you want, because it leaves burrs.
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