Coil spring specification that measures the diameter in between the spring’s outer and inner diameters.
Mean diameter is used to calculate several formulas which are necessary to your design such as index and wire length for manufacturing reasons, or rate to know your spring’s force and working loads.
Coil spring mean diameter can be measured many ways. It is like your spring’s outer and inner diameters except, instead of measuring from the outside of the coil or the inside of the coil, you will measure from in between these spring dimensions; from the center of the coil’s wire. The formula and diagram to calculate coil spring mean diameter are the following.
To calculate mean diameter you must simply either subtract one wire diameter from the outer diameter or add one wire diameter to the inner diameter.