# View of parallel coil spring

On the view of the parallel coil spring, the outline of each coil is drawn as a straight line. 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. 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.

(1) Diameter of spring wire D: the diameter of steel wire for manufacturing 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. That is, N1 = n + N2
(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) Spring direction: it can be divided into left-right rotation, right-hand rotation is commonly used, and right-hand rotation is generally used for those not specified in the drawing.
(12) Spring winding ratio; the ratio of pitch diameter D to steel wire diameter D