Method of connecting a tubular member with an annular member

A method of connecting a tubular member with a cam member, for manufacturing a camshaft thereby, comprising the steps of:

• fitting said tubular member into a central bore in said cam member, the inner circumference of the cam member being provided with axially extending grooves defining substantially flat bottom ridges and substantially flat bottom valleys located only in the lobe part of the inner circumference of the cam member corresponding to the part of the inner circumference of the cam member corresponding to the part of the cam member with the greatest wall thickness, so that the inner circumference is not smooth, the width of the grooves being no less than 1.5 times the wall thickness of the tubular member and being substantially rectangular in cross section;
• placing said cam member in a bulge mold;
• supplying a working fluid into the interior of said tubular member and applying sufficient pressure to the working fluid to forcibly expand the tubular member in an area adjacent the thickest lobe part of the wall of the cam member so that at the outer circumference of the tubular member is deformed in said area and engaged into said valleys so as to form corresponding blunt projections on the outer circumference of the tubular member, so that the outer circumference is not smooth, without substantially reducing its wall thickness;
• and
• terminating said application of pressure to the working fluid when said projections on the outer circumference of the tubular member are sufficiently engaged into said grooves to mechanically lock both members together, such termination of pressure being before the tubular member is completely deformed along the shape of the grooves so as to leave some clearance between the inner wall of the grooves and the expanded outer circumference of the tubular member.