Abstract: Useful portions in the fish heads W are collected from a number of fish heads W of the same kind of fish and of roughly same shape, pituitaries M. A useful portion line is preliminarily determined which passes pituitaries M as useful portions of the number of fish heads W having different sizes when the fish heads W are rested in a specific posture, and each of fish heads W to be processed is rested in the specific posture, and the rested fish head W is cut in the vicinity of the preliminarily determined useful portion line substantially along the useful portion line to expose an useful portion, and a brain as an untargeted portion which is present in a cut surface F is removed to expose the pituitary M, and the exposed pituitary M is collected.

Abstract: From a number of fish heads W of the same kind of fish and of roughly the same shape, pituitaries M as useful portions in the fish heads W are collected. A useful portion line is preliminarily determined which passes pituitaries M as useful portions of the number of fish heads W having different sizes when the fish heads W are rested in a specific posture, and each of fish heads W to be processed is rested in the specific posture, and the rested fish head W is cut in the vicinity of the preliminarily determined useful portion line substantially along the useful portion line to expose an useful portion, and a brain as an untargeted portion which is present in a cut surface F is removed to expose the pituitary M, and the exposed pituitary M is collected.

Abstract: The improved hourglass worm gear which has been produced by grinding a blank for the worm gear by rotating a grinding wheel about a grinding wheel shaft A while turning the grinding wheel shaft A about a tool shaft A3 which extends in parallel with a wheel shaft A2 perpendicular to a worm shaft A1 is characterized in that a cross-sectional shape of the grinding wheel taken in a plane inclusive of the grinding wheel shaft A exhibits a circular arc.Since the cross-sectional shape of the grinding wheel for successively grinding a series of gear tooth surfaces on the hourglass worm gear is contoured in the form of a circular arc, the hourglass worm gear assures that a radius r of the circular arc has an increased degree of freedom and an ideal contact pattern can be obtained by properly adjusting the radius r.

Abstract: The improved hourglass worm gear which has been produced by grinding a blank for the worm gear by rotating a grinding wheel about a grinding wheel shaft A while turning the grinding wheel shaft A about a tool shaft A3 which extends in parallel with a wheel shaft A2 perpendicular to a worm shaft A1 is characterized in that a cross-sectional shape of the grinding wheel taken in a plane inclusive of the grinding wheel shaft A exhibits a circular arc.Since the cross-sectional shape of the grinding wheel for successively grinding a series of gear tooth surfaces on the hourglass worm gear is contoured in the form of a circular arc, the hourglass worm gear assures that a radius r of the circular arc has an increased degree of freedom and an ideal contact pattern can be obtained by properly adjusting the radius r.