 # Compression Spring Terms You Should Know

If you are trying to make a device that uses springs or need to buy a compression spring replacement for your machine you need to know the different names and parts of a compression spring. There are 6 main dimensions of a compression spring that you need to know and be able to identify. Once you can identify these then you can move on to understanding other important terms such as Coil Count, Spring Index, and Spring Rate that all form part of comprehending the function of the spring. These will be discussed in separate articles. In this article we will focus on the most basic and simple which is to describe and explain the most basic parts of a compression spring. These can sometimes be abbreviated and we will list both the abbreviations and description here. ### 1. WD = Wire Diameter

Definition: The outer measurement of the diameter of round spring wire, sometimes called wire thickness. It is measured in decimals or millimeters.

### 2. OD = Outer Diameter

Definition: The measurement of the Outer diameter of the outside coils of the spring’s body

### 3. ID = Inner Diameter

Definition: The measurement of the Inner diameter of the inside of the coils. It is calculated by subtracting two wire diameters from the outer diameter, this will give you the inner diameter.

### 4. MD = Mean Diameter

Definition: The medium or intermediate diameter that is located right in the middle of the inner diameter and outer diameter.

This is calculated by subtracting one wire diameter from the outer diameter or by adding one wire diameter to the inner diameter.

OD - 1 WD or IN + 1WD

### 5. FL = Free Length

Definition: The actual length of a compression spring without the spring being compressed or have any sort of load or force being placed on it. In other words, the measurement of the spring`s overall length from end to end or tip to tip is called “Free Length”.

### 6. P = Pitch

Definition: Spring pitch is the distance in between a compression spring’s adjacent coils from center of wire to center of wire.

The pitch of a spring is the distance from the center of one coil to the center of the adjacent coil, like the threads (lead) on a bolt or screw.

Pitch is sometimes confused with a gap or the space in between the coils, but it is the distance or space from one coil to the center of the other adjacent coil.

#### Understanding Spring Terms One Step at a Time

At Acxess Spring we understand how hearing tons of terminology, formulas and trying to understand the science behind a spring design can be a bit overwhelming. That is why we have dosified our information into different articles which you can find and search through by clicking HERE.