Cabide tipped chucking reamers (Figure H-123) are often used in production setups, particularly where abrasive materials or sand and scale(as in castings) are encountered. The right-hand helix chucking reamer (Figure H-124) is recommended for ductile materials or highly abrasive materials or when machining blind holes. The carbide tipped left-hand helix chucking reamer (Figure H-125) will produce good finishes on heattreated steels up to RC 40. They should be used only on through holes because the chips push out through the hole ahead of the reamer. All expansion reamers (Figure H-126) after becoming worn can be expanded and resized by grinding. This feature offsets normal wear from abrasive materials and provides for a long tool life. These tools should not be adjusted for reaming size by loosening or tightening the expansion plug but only by grinding.