There is a need in various types of machinery for metal parts having external and internal shapes whose dimensions must be held within extremely close tolerances. Moreover, such parts may require that the internal and/or external configuration be perpendicular to the plane of the part. When such parts are manufactured by prior art techniques, such as milling, shaving and hobbing it is both difficult and expensive to maintain close dimensional tolerances and to avoid stressing the material with a consequent distortion of the part. The problem is accentuated where the parts are formed of hard materials, such as tool steel.
By way of example, when using prior art techniques it has been very difficult and costly to manufacture relatively thin gears having the sizes or working surfaces of the gear teeth extending at straight angles, i.e., perpendicular to the planes of the gears. Such gears have been made in the past by shaving the blanks to the desired shapes and subsequently heating and flattening the parts. Not only have the shaved surfaces not always been acceptable but the cost of reworking the shaved parts to restore the required flatness has been excessive except in the case of a few extremely necessary parts.