Method of generating involute tooth forms with a milling cutter

In the manufacture of a gear, the method of machining a gear blank to produce a tooth profile which is involute from an imaginary base surface of revolution within said gear blank, said surface having a straight-line generatrix and having an imaginary plane of action tangent to said surface,

• said method comprising the steps of
• rotating a cutter having a plurality of cutting edges uniformly spaced about the entire periphery of the cutter sweeping a cutting path in the form of a surface of revolution about the axis of the cutter so that said plurality of cutting edges are distributed substantially uniformly about the common surface of revolution which they define, said cutting-path surface comprising a plunge-cutting rim portion of cutting thickness not exceeding the desired tooth space at the tooth root and a contiguous tooth-profile cutting portion,
• positioning the rotating cutter on the side of said plane of action opposite to said base surface with said rim portion penetrating said plane of action and with said tooth-profile cutting portion intersecting said plane of action along a predetermined generating line and with said tooth-profile cutting portion perpendicular to said plane of action at least at the center of said generating line,
• independently controlling the rotation of the cutter, and
• effecting a relative feeding movement of said gear blank and rotating cutter independently of the rotation of the cutter while maintaining the aforesaid position of the cutter relative to said plane of action,
• said feeding movement being such as:
• to cause a relative rolling motion between said base surface and said plane of action without slippage;
• to cause said generating line at all points therealong to maintain a controlled angularity with respect to the instantaneous direction of its movement relative to the line of tangency of said base surface with said plane of action during said rolling motion;
• and
• to cause said rotating cutter to penetrate said gear blank and said generating line to traverse said gear blank between its addendum surface and a depth at which the desired active tooth-profile is achieved at the center of said generating line.