Extension Springs FAQ
What is the difference on an extension spring with “crossover” style ends verses “machine”?
As you can see from the chart below on a crossover the wire leaves the body of the spring and first crosses over the middle of the spring while the machine style comes up off the body first. Crossover tends to be cheaper than machine to form. Crossovers aslo are used on smaller spring with wire sizes .047 and under and outside diameters .500 and under.
|End style - crossover||End of extension spring which is formed by coming across the center of the spring then forming a circle for the end.|
|End style - machine||End of extension spring which is formed by coming directly off the body then forming a circle across the center for the end.|
What is the difference between and extension spring with a “loop” verses a “hook”?
As you can see from the pictures below, a spring with a hook has a gap form the end of the wire to the body while a loop is a complete circle and has no gap.
|End type - hook||End of extension springs with one coil in which there is a gap between the coils and the end of the wire.|
|End type - single loop||End of extension springs with one coil in which there is no gap between the coils and the end of the wire.|
What is the “initial tension” of an extension spring?
It is the amount of force in pounds that it takes to first open up the coils of an extension spring. We measure the force when a sheet of paper fits between the coils when is starts to extend.
What are the differences in hook relationships that are available for an extension spring?
Below are the three most common relationships that an extension might have. Also not shown is “random” which is the cheapest of all and should be noted on all prints if it’s not an important factor in the application.
|Relationship of ends||The relative position of the plane of the hooks or loops of an extension spring to each other measured in degrees