| 摘要 |
The method involves cutting a disc shaped blank (1) from a metal sheet and piercing the disc to form an axial hole (2). the disc is grooved circumferentially in a transverse plane to define a pair of diverging flanges (7a,7b). The flanges are formed into a sleeve (10) which is cylindrical having a medial groove (11). An annulus is cut out of the sleeve to form a pair of projections (15). The two opposing sections are then threaded in opposite directions.
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