Spring plunger
A spring plunger or detent spring is a spring-loaded mechanical part to ease indexing, positioning, securing, and disassembling of objects without losing parts. The spring force keeps the pin in position during normal use.
Typically, it is a machine part consisting of a hollow cylinder with an internal compression spring acting on a pin. The pin may, for example, be shaped as a rod with either a cylindrical or rounded tip, or a spring-loaded ball if the spring acts against a ball.
Manufacture
Spring plungers can be supplied as a complete unit that is mounted into the workpiece by screwing into threads, or in a pluggable version that is pressed into the workpiece. The sleeve is usually made of free machining steel.Alternatively, it can be made directly into the workpiece by drilling and tapping a hole, then inserting a pin, spring, and finally a set screw.
The spring force is tuned for the intended use. In spring plungers with a screw, the spring pressure can be adjustable within a certain working range.
Different plungers may require different tools for installation, such as a hex key, socket wrench, or flathead screwdriver. Blind hole mounting variants may have tool slots on the same side as the pin.
Materials
At high temperatures or when the parts are exposed to aggressive chemicals, plastic balls or balls made of corrosion-resistant materials such as silicon nitride can be used. The threaded sleeve is then typically made of stainless steel instead of carbon steel.Use
Spring-loaded plungers have a wide range of uses.Some spring plungers are designed to be handled only when assembling or occasionally adjusting equipment. Other spring plungers are designed to be routinely manipulated, and may have an integrated operating lever that is pushed in or a lever that is pulled out to manipulate the object.
Similar principles are used in spring-loaded valves and valve stems, or automatic ejectors on firearms.