A tube having sealing ring grooves formed by a sequential rotational process and a shock absorber including the tube, in which durability of a sealing ring fitted in each of the sealing ring grooves is enhanced. An inclination angle (1) formed with respect to a plane (PL1) perpendicular to an axis of a separator tube by a side surface of the sealing ring groove, which is located on an opening end side of the separator tube, is set to 8 or more. With this, a maximum tensile stress to be applied to an O-ring can be reduced to be smaller than a maximum tensile stress in a case of using a backup ring. As a result, the durability of the O-ring can be set equivalent to or enhanced to be higher than durability in the case of using the backup ring.

The invention concerns a process for roll straightening crankshafts (8, 8) using crankshaft deep rolling tools (1 to 7), in particular work rollers (18,19) which, while the crankshaft (8, 8) is rotated about its axis of rotation (21), are pressed into the recesses (14 to 17) or radii that delimit the bearing pins (Hi, Pi) on either side with a roll straightening force (27, 30) that constantly fluctuates around the circumference of a bearing pin (H.sub.1 to H.sub.5, P.sub.1 to P.sub.4). Roll straightening is carried out by determining the individual vector (34) of the runout by size and direction (35) at each main bearing (Hi) of the crankshaft (8, 8). The largest (45) or resulting vector (25) is determined from the individual vectors (34), then the main bearing pins (Hi) and crankpins (Pi) of the crankshaft (8, 8) are roll straightened with a roll straightening force (27, 30, 49, 50) the size (25) and direction (26) of the largest (45) or resulting vector (25) of which is between 0 and a multiple of the largest (45) or resulting vector (25).

Provided is a method of forming a locking ridge for a case of forming the locking ridge on an outer peripheral surface of a joint portion by form rolling, the method realizing a joint portion structure which is superior in pipe detachment prevention performance when pipes with locking ridges are connected by fixing pipe ends with a housing. Using a convex roller arranged inside the workpiece pipe body and a forming circular groove arranged outside the pipe body, the locking ridge is form-rolled such that an upright wall portion thereof is raised at an angle of at least 65 and no greater than 90 with respect to the outer peripheral surface in the pipe axis direction, and that a height of the locking ridge from the outer peripheral surface to the apex of the tip portion is at least a total of curvature radii of faces of the processing means in contact with the pipe body.

A method of manufacturing a metal mask includes calendering a metal material, so as to form a metal mask substrate, where the metal mask substrate includes a surface and a plurality of grooves formed in the surface, and the grooves all extend in a direction. The surface has at least one sampling region, while at least two grooves are distributed in the sampling region, where an average area ratio of the area of the grooves within the sampling region to the area of the sampling region ranges between 45% and 68%.