They generally have a lug across the I.D. of the spring, which engages a slot in the shaft, over which it works. The I.D. can be made with holes to engage an arbor protrusion or can be made in a special shape to fit over a similar shaped shaft. The outside end can be formed as per customer's requirement.
These are generally made of rectangular section material, flat strip, with round edges or normal slit edges with equal or increasing space between coils. Therefore, these are generally used for less than 3600 rotational applications. These are wound flat to achieve torque. For first 3600, torque delivered per revolution is linear. If the these springs are totated more than one turn the coils will touch each other causing friction leading to erratic loads.
Application of Sprial Springs : These are general used as brush springs in D.C. mortors, anti-backslash springs, Alternators, Drill presses, Vertical mill, Counter balance springs etc.
