fitted therein as seen in fig2 the outer retainer 1 has the tapered surface 1 e the tapered surface 1 e abuts against an inside edge of the outer ring 50 when the one way clutch 10 is inserted into the outer ring 50 thus the outer retainer 1 is guided by the outer ring 50 in a manner to bring its axis into accurate alignment with the axis of the outer ring 50 accordingly the one way clutch 10 is smoothly inserted into the outer ring 50 hence the one way clutch 10 is readily assembled in the outer ring 50 when elevated in temperature in the practical use the one way clutch may suffer the occurrence of cracks in a few cases in the thermally expanded outer retainer 1 as shown in fig1 tensile stress is produced in its inside circumferential surface 1 h because its opposite ends tend to deform in directions of the arrows in the figure this may result in a crack x it is thought that such a phenomenon results from that a contact width w 1 between the outer retainer 1 and the outer ring 50 is considerably smaller than an overall width of the outer retainer 1 second and third embodiments of the present invention hereinbelow contemplate the prevention of the occurrence of such cracks fig1 to fig1 illustrate a one way clutch 20 according to the second embodiment which differs from the first embodiment in the mode of an outer retainer 11 fig1 is a front view of the outer retainer 11 including a fragmentary sectional view whereas fig1 is a sectional view taken on the line xiv u2014 xiv in fig1 fig1 is a view seen along the arrow xv in fig1 whereas fig1 is a perspective view of the.