Method of making a fluid coupling

A method of making a fluid coupling comprising a first and a second coupling member having respective fluid channels communicating with each other, a gasket interposed between abutting end faces of the two coupling members and screw means for fastening the two coupling members together, each of the first and second coupling members being provided in the end face thereof with an annular recessed portion having a flat bottom face, the gasket being annular and disposed within a space defined by the recessed portions of the two coupling members, the gasket having an annular ridge formed on each of opposite side surfaces thereof,

• the fluid coupling making method being characterized in that the ridge of the gasket has a trapezoidal cross sectional shape defined by an outer tapered face providing an outer peripheral surface, an inner tapered face providing an inner peripheral surface and a flat face providing a top end surface, the hardness of the gasket, the angle between the tapered faces of the ridge, the height of the ridge and the area of the flat top end face of the ridge being so determined that the value of thrust for tightening up the coupling is between a predetermined minimum value and a predetermined maximum value.