A magnetic tape cassette and a guide roller in which the magnetic tape can stably
travel and the magnetic head can read/write the record correctly, and a method
of manufacturing the guide roller are provided. The magnetic tape cassette of the
present invention comprises a guide roller 106 rotatably supported by the
lower cassette half. The guide roller is almost in the shape of a barrel of which
a coefficient of curvature T expressed by the expression [1] representing the extent
of curvature of the circumferential surface is in the range between 0.001 and 0.01,
and comprises a primary molding and injected resin injected within the primary
molding for bulging said primary molding into the shape of said barrel shaped cavity
that has a largest diameter at the parting line by the injection pressure.
