# Knowledge of hardware spring

Spring is a kind of elastic element widely used in mechanical and electronic industries. When loaded, the spring can produce large elastic deformation and convert mechanical work or kinetic energy into deformation energy. After unloading, the deformation of spring disappears and returns to its original state, and the deformation energy is converted into mechanical work or kinetic energy.

The main functions of springs are: 1) measuring force, such as springs of spring scales and gauges; 2) controlling movement, such as clutch, brake and valve control spring; 3) damping and buffering, such as springs of buffer and shock absorber; 4) energy storage or energy transmission, such as springs on clocks, meters and automatic control mechanisms.

2. Types of spring: there are many types of spring, including compression spring, tension spring, torsion spring and wire forming.
3. Name and dimension relationship of each part of spring:
(1) On the diameter of spring wire D: the diameter of steel wire for making spring.
(2) Spring outer diameter D: the maximum outer diameter of the spring.
(3) Spring inner diameter D1: the minimum outer diameter of the spring.
(4) Spring pitch diameter D2: the average diameter of the spring. Their calculation formula is: D2 = (D + D1) △ 2 = D1 + D = d-d
(5) T: in addition to the support ring, the axial distance of the corresponding points on the pitch diameter of the two adjacent coils of the spring becomes the pitch, expressed by T.
(6) Effective number of turns n: the number of turns in which the spring can maintain the same pitch.
(7) The number of support rings N2: in order to make the spring work evenly and ensure that the axis is vertical to the end face, both ends of the spring are often tightened during manufacturing. The number of parallel tight turns only plays a supporting role, which is called supporting ring. Generally, there are 1.5T, 2T and 2.5t, and 2T is commonly used.
(8) The total number of turns N1: the sum of the effective number of turns and the supporting ring. N 2 = n 1
(9) Free height H0: the height of spring without external force. From the following formula: H0 = NT + (n2-0.5) d = NT + 1.5D (when N2 = 2)
(10) Spring development length L: the length of steel wire required for winding the spring. L ≈ N1 (л D2) 2 + N2 (compression spring) l = л D2 n + unfolded length of hook (tension spring)
(11) Spiral direction: there are left and right rotation, commonly used right-hand rotation, the drawing does not indicate the general use of right-hand rotation.

4. Specified drawing method of spring:
(1) On the view of parallel coil spring line, the outline of each coil is drawn as a straight line.
(2) For springs with more than 4 effective coils, only 1-2 coils at both ends can be drawn (excluding support rings). The middle is connected by a dotted line through the center of the spring wire.
(3) In the drawing, when the rotation direction of the spring is not specified, the spiral spring is all drawn as right rotation, and the left rotation spring is also drawn as right rotation, but the word “left” should be marked.