Patent ID: 8807298

Claim:
A disk brake having a cylinder slidably accommodating a piston that presses a brake pad against a disk, said cylinder comprising a plate-shaped cover member constituting a bottom of said cylinder and a cylinder body having an opening that is closed with said cover member, said cover member being integrally joined to said cylinder body to close the opening, and, after said cover member has closed the opening, an opening-side end surface of said cylinder body is subject to face cutting to make the end surface flat, wherein the cover member is joined to the cylinder body by friction stir welding, wherein said cover member has a projection on one side of said cover member and a blind hole on the other side of said cover member, said cover member further comprises an outer peripheral surface which can be fitted into said opening at the same axial position with any of the one side and the other side facing an inside of said cylinder, before jointing of said cover member to said cylinder body, wherein, after said friction stir welding of said covering member and said cylinder body, the projection of said cover member is positioned so as to face the inside of said cylinder, wherein the blind hole is sized so as to be contained inside an inner circumferential edge of a circumference defined by weld beads formed by a welding tool during the friction stir welding between the cover member and the cylinder body, wherein a circumferential wall and a bottom portion of the blind hole remains even after said face cutting of the weld beads, and wherein the projection and the blind hole are circular in cross section, and the blind hole is smaller than the projection in diameter.