A method of resecuring a camshaft gear to a camshaft after the camshaft gear has been removed to service an engine wherein the camshaft remains in the engine comprising: tapping a channel in an end of the camshaft where the camshaft gear is removed; securing a forcing screw within the channel; placing the camshaft gear on the camshaft; and rotating a forcing nut on the forcing screw until the camshaft gear is seated and secured on the camshaft.

An indexable thread forming tap including: a body in a shaft shape; and a tip concentrically and detachably attached to a leading end portion of the body by screw-fastening and rotationally driven around an axial center along with the body for rolling of a female thread, the body being disposed with a screw hole concentrically to the axial center such that a screw shaft disposed on the tip concentrically to the axial center is screwed into the screw hole for the screw-fastening, a leading end surface of the screw shaft being pressed against a bottom surface of the screw hole into close contact with each other by the screw-fastening to integrally fix the tip to the body without the leading end of the body abutting on the tip, the body being disposed with a restraining hole concentrically to the axial center.