When a disc spring is assembled with single, double, and triple parallel sets in series, the discs will flatten consecutively when loaded. The characteristic of such a spring stack changes progressively. The same result is obtained when disc springs of various material thicknesses are stacked in one column. It becomes obvious that single sets, or discs made of thicker material, will be subject to considerable stress when disc springs of standard design are used. This excess stress can be eliminated; however, by decreasing the formed height of a disc or by using space washers or rings to limit deflection.