# Helical Spring Calculations

#### Step 1.) Enter your helical spring's dimensions

When working on a spring design, the first thing you must do is measure your spring’s surroundings to make sure that your spring will fit correctly when being installed. If it is going over a shaft, make sure you have a few thousandths of an inch of clearance between the shaft and the helical spring’s inner diameter so that you avoid friction when the spring is traveling down. The same goes for your spring’s outer diameter if it is being installed inside a hole or if there are other parts in your mechanism around it. Make sure that there is some clearance between the helical spring’s outer diameter and its surroundings. Keep in mind that adjusting the wire diameter will affect the coil diameters as well. The diameters will either increase by two thousandths of an inch or decrease by two thousandths of an inch if you increase or decrease the wire diameter by one thousandths of an inch. This means it will increase or decrease double the quantity of adjustment.

The free length must be measured from the distance between the “ground” where the spring will be standing and the part of the mechanism that will be applying the load to compress the spring. It is recommended that you add a few more thousandths of an inch so that you generate preload for the spring to stay in its place. For the total coils, you must consider the solid height because you must make sure you will be able to meet your loaded height. The difference between the two is that the solid height is the height of your helical spring’s coils when they are fully compressed and the loaded height is the height you require for the spring to have after you’ve applied a load to fulfill a certain distance traveled according to your helical spring’s rate. Your spring’s end type is also considered in this calculation and the active coils will be affected by it.

The most common type of ends are closed and squared ends. With closed ends, your helical spring’s total coils will be two more than the active coils since the coils on the ends are closed thus not active. In the case of double closed ends, your helical spring will have 4 total coils more than the active coils. When it comes to closed and ground ends, it works the same way except you will subtract one wire diameter from the solid height since you’re taking out half a wire diameter from each end when they’re ground. Only when you have open ends are the spring’s total coils and active coils the same. In the examples to the right you will see the helical spring calculations explained in this text.