Method for hardening camshafts

A method for hardening axially spaced cams of elongated camshafts, each camshaft having an axis of rotation and a plurality of cams axially spaced along said axis and with the cam lobes of each cam having an axially outwardly projecting tip at a preselected circumferential orientation, said method comprising the steps of:

• (a) providing a first induction heating coil having a generally circular inner surface and an electrically insulating gap at a selected location on said inner surface of said first heating coil;
• (b) providing a second induction heating coil having a generally circular inner surface and an electrically insulating gap at a selected location on said inner surface of said second heating coil;
• (c) providing a first power supply for energizing said first heating coil;
• (d) providing a second power supply for energizing said second heating coil;
• (e) mounting one of said camshafts with said axis extending through said first heating coil;
• (f) mounting one of said camshafts with said axis extending through said second heating coil;
• (g) causing relative movement of said one camshaft axially with respect to said first coil until a first of said cams is within said first coil;
• (h) causing relative movement said one camshaft axially with respect to said second coil until a second of said cams is within said second coil;
• (i) circumferentially indexing said one camshaft with respect to said first coil until said tip of said first cam is adjacent said electrically insulating gap of said first coil;
• (j) energizing said first coil by said first power supply to heat said first cam to a predetermined temperature in its circumferentially indexed position;
• (k) applying a quenching media to said first cam while it is within said first heating coil;
• (l) circumferentially indexing said one camshaft with respect to said second coil until said tip of said second cam is adjacent said electrically insulating gap of said second coil;
• (m) energizing said second coil by said second power supply to heat said second cam to a predetermined temperature in its circumferentially indexed position;
• (n) applying a quenching media to said second cam while it is within said second heating coil;
• (o) then indexing a first subsequent unhardened cam axially into said first heating coil and a second subsequent unhardened cam into said second heating coil;
• and,
• (p) again actuating said first and second energizing means to heat said first and second subsequent cams with said first and second heating coils, respectively, including the steps of quenching said cams.