Abstract: A clutch diaphragm comprises a peripheral Belleville ring portion and a central portion having a central aperture and comprising a set of radial fingers separated by slots, each of which extends from a blind end which is close to the peripheral portion to an inner end which is open into the central aperture, the latter being common to all of the slots.In a method of making this diaphragm, a flat blank is heat treated and is then soaked and hot formed to give the diaphragm a first diaphragm angle. It is then tempered in a tempering oven. The diaphragm is then transferred from the tempering oven to a stabilizing press, in which the conicity of the diaphragm is reversed while it is still hot from the tempering oven, so that instead of the first angle it now has an inversion angle.