| 摘要 |
A head of a wrench comprises a hole having a center and a radius. The head further includes a compartment communicated with the hole. A wall defining the compartment has a center of curvature and a radius of curvature. A ratio between the radius of curvature of the wall and the radius of the hole is equal to or greater than 0.5, but less than 1. A distance between the center of the hole and the center of curvature of the wall is selected to form a deeper compartment to thereby improve the torque-bearing capacity.
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