| 摘要 |
PROBLEM TO BE SOLVED: To extend longevity of a rolling element and a holder by protecting them from small metal pieces such as abrased powder, chips, etc. SOLUTION: A holder 5 is formed of a resin material and is constituted by providing a hard metal layer 8 made of a hard metal material to cover an outer peripheral surface 6A, an inner peripheral surface 6B, each of end surfaces 6C of a ring body 6 and an inner surface 7A of each of pockets 7. Consequently, it is possible to eliminate breakage of a ball 4 and the holder 5 by these small metal pieces by the hard metal layer 8 having hardness of more than the same as the small metal pieces such as the abrased powder, the chips, etc., mixed in lubricating oil even in the case when a lubricating method in an oil bathing state is adopted. Additionally, it is possible to protect the whole of the holder 5 from lubricating oil and metal pieces as the hard metal layer 8 is formed to cover the whole of the holder 5.
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