| 摘要 |
a substantially cylindrical outer cylinder having a plurality of loaded ball bearing grooves and nonloaded ball guide grooves formed on the inner peripheral surface; a cylindrical ball retainer received on the outer cylinder and having an axial length greater than that of the outer cylinder and provided on the outer peripheral surface; a pair of ring-shaped end covers fitted and welded to both axial end portions of the ball retainer projecting beyond both ends of the outer cylinder, each of the end cover being provided on the inner surface thereof with ball-turning grooves which radially confront the ball- turning grooves of the endless track grooves.
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