Wind Direction Die springs are wound in either a clockwise or counter-clockwise direction. Since the load is applied laterally, wind direction is usually unimportant. Dimensions Free length is the length of the die spring before it is subject to a load or preload. Hole diameter is the outer diameter of the spring, or the overall width of the spring which will increase under compression. Rod diameter is the inner diameter of a die spring, which is intended to slide over the guide rod in die machinery. Wire diameter is the width of the wire used to make the coil. Spring dimensions; Image source Spring Masters Performance Elastic limit is maximum compression a die spring can handle before deformity. Preload is the distance of free length reduced by a consistent load on the spring. Operating travel is the distance subtracted from the spring length after operating load has been applied. Compressed length is the overall length of the spring after the preload and operating travel has been accounted. Solid height is the length of the die spring when all adjacent coils are resting on each other under load. Spring rate is the amount of load needed to compress a spring a measure distance. In die springs, this can be measure in thousands of pounds/kilograms. Safety Die spring production is closely monitored to ensure quality springs under heavy duress, so die springs should not be altered in any way by a consumer. Corrosive elements like lubricants and chemicals may shorten a spring's lifespan, as will misaligned or mismanaged spring rods/guides. Die springs should be routinely cleaned, and all springs in a set should be replaced at the same time to maintain a uniformed yield.