Compression spring is under axial pressure of the spiral spring, it is used in the data section for more rounded, useful also rectangle and multi-strand steel rolled a travelling, spring is usually pitch, such as the shape of the compression spring are: Cylindrical, conical, convex and concave and a small amount of noncircular, compression spring there is a certain gap between circle and circle, when under external load spring contraction deformation, deformation energy storage.
Extension spring is a spiral spring that bears axial tension. The extension spring is usually made of circular section material. When not under load, the tension spring between the ring and ring are generally not tight clearance. It is widely used in machines and instruments to control the movement of parts, store energy and measure the size of force. The hooks are in the form of side hook spring, long hook spring, english hook spring, german hook spring, half-round hook spring, duck beak hook spring, etc. The materials are stainless steel, qin steel, high carbon steel, phosphorous copper, oil tempered alloy spring steel, etc.