Slot Scraper for removing fins of mica and burs of copper from the edges of commutator bars after undercutting with a U-shaped saw. Do not use for undercutting mica because any tool that rakes out the mica may injure the insulation by tearing out mica slivers and thus permitting dirt to work down into the insulation. - Martindale Electric Adjustable Slot Scraper, Material: High Speed Steel.