Abstract: A method of forming a ridge in a cylindrical tube member comprises placing the ends of the tube member into spaced-apart dies so that each die is a close fit around the respective end of the tube member, and the tube member has a free portion between the ends. Liquid is supplied to the interior of the tube member and the liquid pressure within the tube is increased so that its free portion bulges radially outwardly. While the radial bulge of the free portion of the tube member is continuously measured on the outside, the liquid pressure is gradually increased depending on the radial bulge measured until a pre-determined radial bulge is measured. Thereafter, while the liquid pressure is maintained in the tube member, the dies are axially moved towards each other until they are spaced a pre-determined axial distance apart. During this displacement the dies deform the bulge until the desired ridge form is reached.