cut from sheet metal as shown in fig2 a and 2b fig2 a and 2b show the front plate 34 as having a hollow center 56 to accommodate the valve disk bolt 36 and the back plate 42 also having a hollow center 58 to accommodate passage of the compression spring the back plate 42 can have a solid center 58 if no passage for the compression spring 22 or other components is required the front flexure plate 34 may be attached to the disk 18 by a valve disk bolt 36 or by other suitable means referring to fig2 a and 2b the flexure plate 34 42 is a flat spring made by machining cuts 60 a 60 b through the flat plate each cut 60 a 60 b is along a spiral or spiral like path from near the flexure plate outer diameter 44 52 to near the flexure plate inner diameter 38 48 the shape of the spiral path is the same in the figure shown they are the same this is not necessarily always the case for each cut 60 a 60 b the spiral cuts are spaced evenly around the plate in the figure shown they are the same this is not necessarily always the case so the radial angles between the cuts 62 a 62 b of coinciding cuts are equal the flexure plates 34 42 can have fewer or more.