Coupling, particularly for coupling a high-pressure pump with a gear wheel pump

The clutch (1) has a clutch piece (2) comprising two-planes (4), and another coupling piece (3) comprising a clutch slot (5). The two-planes are partially engaged with the former clutch slot, and an inner side (19) of the clutch slot acts in a pressure region (17). The two-planes are provided in a pressure region for transmitting torque between the clutch pieces, and the inner side of the clutch slot is partially formed with a convex contour (20) that is partially provided in a longitudinal side (21) of the clutch slot. The convex contour is formed with a determined curvature radius.