Close-tolerance heat treatment of gears

Heat treatment distortion still conjures up images of gross and uncontrollable twisting, bending and warpage combined with growths and shrinkages striking fear and apprehension into designers and manufacturers. Gears are critical artifacts because even the smallest variations can severely undermine load-carrying capacity end noise abatement. Even ASM Handbook Volume 4 defines distortion as "an irreversible and usually unpredictable change of size and shape". By developing a methodology for a wide range of shapes and sizes for carburise case-hardened gears, we can demonstrate predictability of distortion and growth which is not always irreversible.