Patent ID: 7950504

Claim:
A disk brake for pressing a brake pad against a disk, the disk brake comprising: a cylinder comprising: a cylinder body having a bore and an opening at a bottom thereof, the bore adapted to have a piston slide therein, in response to a fluid pressure, to press the brake pad against the disk; and a lid member that closes the opening, wherein said lid member is joined to said cylinder body by friction stir welding, and wherein said cylinder body has a bottom portion located at said bottom of said cylinder body where the opening is formed, and wherein said bottom portion has: an outer end surface disposed opposite from a surface bordering the bore in an axial direction of said cylinder body; an outer peripheral surface with an outer diameter that is larger than an outer diameter of a minimum outer diameter portion of an outer peripheral wall of the bore of said cylinder body; and a bulge portion projecting radially outward from a part of said outer peripheral surface, said bulge portion having a flat surface continuous from the outer end surface of said bottom portion, and said bulge portion being an end point of the friction stir welding.