Method of making a diaphragm, especially for a motor vehicle clutch

A method of making a motor vehicle clutch diaphragm which in its relaxed state is generally frusto-conical defining a diaphragm angle complementary to its cone half angle, the diaphragm comprising a peripheral portion defining a Belleville ring and a central portion joined to the peripheral portion and having a central aperture, with a plurality of slots extending from an open end proximate said central aperture to a blind end proximate said peripheral portion so as to define a plurality of radial fingers between the slots, wherein the method includes the steps of:

• heat treating a metal blank;
• soaking and hot forming said heat treated metal blank so as to define a partly formed diaphragm having a first diaphragm angle, said first diaphragm angle being of a frusto-conical shape;
• tempering said partly formed diaphragm in a tempering oven;
• transferring said partly formed diaphragm from said tempering oven to a stabilizing press;
• reversing the frusto conical shape of said partly formed diaphragm while still hot from said tempering oven, wherein said first diaphragm angle is converted to a second diaphragm angle, said second diaphragm angle being an inversion angle with respect to said first diaphragm angle.