Method and apparatus for hardening cam lobes on a camshaft

Apparatus for inductively heating and hardening the peripheral surfaces of like contoured finish ground cam lobes axially spaced closely apart a distance less than their axial thickness and in different circumferentially oriented locations on a camshaft having a longitudinally extending rotation axis, said apparatus comprising:

• means mounting said camshaft for axial movement along and rotative index movement about a work axis coinciding with said rotation axis, an inductor mounted in a fixed position about said work axis and comprising a single conductor loop with a ring-shaped inner surface encircling said work axis and contoured to correspond to substantially the entire surface profile of said cam lobes, said inductor being adapted to receive the cam lobes individually in inductive heating position therein in the same rotatively oriented position about said work axis as the said inner surface contour of the inductor and provide a uniform minimal coupling gap therebetween of less than about 0.1 inch around the full peripheral extent of the cam lobe, said camshaft mounting means being operative to axially and rotatively index the camshaft relative to said inductor to position each of the said cam lobes individually in said inductor in the said same rotatively oriented position therein, high frequency power supply means connected by input leads to said inductor for selectively energizing said inductor at a frequency greater than 200 KHz and with a high intensity power density of at least 25 KW/inch.sup.2 at the surface profile of a said cam lobe positioned in said inductor, means for energizing said power supply, while said cam lobe is positioned in said inductive heating position in said inductor, for a time period less than 1.0 second whereby to inductively heat the cam lobe uniformly therearound to a predetermined elevated heat treating temperature preparatory to subsequent quench hardening without causing unacceptable heat distortion of the finish ground surface profile of the heated cam lobe and without causing stray flux heating and drawback tempering of the previously hardened adjacent cam lobe, said conductor loop having two complementary elongated segments electrically interconnected at one end by a pressure electrical connector and connected to respective said input leads at the other ends, said inductor segments being movable apart laterally outward from said work axis and camshaft from a normal closed position to a separated open position, first drive means for axially moving said camshaft relative to said inductor while in said open position to axially index a cam lobe out of the inductor and a succeeding one of said cam lobes into heating position in said inductor, and second drive means for rotating said camshaft relative to said inductor while in said open position to rotatively index the said succeeding one cam lobe about said work axis into the said same rotative oriented position therearound as the said inner surface contour of said inductor.