Brake disc and method of producing the same

A method of producing a brake disc to be mounted on an axle hub, the brake disc including a pair of sliding surfaces with which friction members respectively come into a sliding contact and which face in mutually opposite directions, the method comprising:

• a first forging step of forging a first member having a disc-like shape and including a mount portion through which the brake disc is mounted on the axle hub and a radially outer portion located radially outward of the mount portion, one of the sliding surfaces being formed on the radially outer portion;
• a second forging step of forging a second member having a doughnut plate shape, the other of the sliding surfaces being formed on the second member;
• and
• a bonding step of bonding the first member and the second member,
• wherein, in at least one of the first forging step and the second forging step, a protruding portion is formed on one of the radially outer portion of the first member and the second member, so as to protrude toward the other of the radially outer portion of the first member and the second member, the protruding portion including a plurality of annular protrusions disposed concentrically and having mutually different diameters, and
• wherein, in the bonding step, the first member and the second member are bonded to each other through the plurality of annular protrusions, and
• wherein the method further comprises a heat-dissipation-hole drilling step of drilling a plurality of heat dissipation holes penetrating the plurality of annular protrusions in a radial direction of the brake disc over an entire circumference of the brake disc.