A cage for an hourglass roller bearing includes an annular ring having a first axial face and a second axial face. A plurality of first rails extend from the first axial face and a plurality of second rails extend from the second axial face. The cage includes a plurality of pockets. Each of the plurality of pockets is defined by opposing circumferentially facing walls of at least one of adjacent pairs of the first rails and adjacent pairs of the second rails. The circumferentially facing walls are arcuately formed so that each of the plurality of pockets is cylindrical.

A self-aligning roller bearing includes an outer ring, an inner ring, spherical rollers, a cage having a plurality of pockets that contain the spherical rollers, and a guide ring. Each spherical roller may be rotated on an imaginary line passing through a contact point at which the spherical roller contacts an outer raceway surface and a contact point at which the spherical roller contacts an inner raceway surface. Each pocket has a clearance between the pocket and a corresponding spherical roller, and the size of the pocket is set so that the rotation of the corresponding spherical roller is limited. The guide ring has such a side-surface shape that a small clearance is ensured between the spherical roller and the guide ring even when the spherical roller is rotated, in the pocket, on the imaginary line by a maximum amount at which the rotation of the spherical roller is limited.

A milling tool includes a main body and a plurality of cutting inserts with respective cutting edges. The main body has an end face and a barrel-shaped curved lateral face. A first group of the plurality of cutting inserts are fastened on the end face, a second group of the plurality of cutting inserts are fastened on the barrel-shaped curved lateral face, and the respective cutting edges describe a barrel shape. Each one of the plurality of cutting inserts may be designed as an indexable insert.

A holder for a self-aligning roller bearing, having a central annular part with lintels fixed on side surfaces thereof in an axial direction and protruding parts which protrude closer to the outer sides in a radial direction than the lintels. The holder includes reinforcement parts fixed to the central annular part and the lintels on outer sides of the lintels in the radial direction and on outer sides of the protruding parts in the axial direction. In cross sections cut out along the axial direction and radial direction, at least a part of a contour line of outer side surfaces of the reinforcement parts in the axial direction extends inwardly in the radial direction while extending toward outwardly in the axial direction. A self-aligning roller bearing having the holder with improved connection strength of connection parts between the lintels and the central annular part prolongs bearing service life.