A spring plunger or detent spring is a

spring-loaded A spring is a device consisting of an elastic but largely rigid material (typically metal) bent or molded into a form (especially a coil) that can return into shape after being compressed or extended. Springs can store energy when compresse ...

mechanical part used for indexing, positioning, and securing of objects, as well as for making objects possible to disassemble in normal use 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 A cylinder () has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infinite ...

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 (broadly categorized as a ''spring plunger''), or a spring-loaded ball ( ball plunger) 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 Free-machining steel is steel that forms small chips when machined. This increases the material's machinability by breaking the chips into small pieces, thus avoiding entanglement in the machinery. This enables automatic equipment to run without hu ...

. Alternatively, it can be made directly into the

workpiece A workpiece is a piece, often made of a single material, that is being processed into another desired shape (such as building blocks). The workpiece is usually a piece of relatively rigid material such as wood, metal, plastic, or stone. After a ...

drilling Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross section (geometry), cross-section in solid materials. The drill bit is usually a rotary Cutting tool (machining), cutting tool, often multi-point. The bit i ...

and

tapping Tapping is a playing technique that can be used on any stringed instrument, but which is most commonly used on guitar. The technique involves a string being fretted and set into vibration as part of a single motion. This is in contrast to stand ...

a hole, then inserting a pin (or ball), spring, and finally a

set screw In American English, a set screw is a screw that is used to secure an object, by pressure and/or friction, within or against another object, such as fixing a pulley or gear to a shaft. A set screw is normally used without a nut (which disting ...

. The spring force is dimensioned 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 A hex key (also, hex wrench, Allen key and Allen wrench, Unbrako or Inbus) is a simple driver for Bolt (fastener), bolts or screws that have heads with ''internal'' hexagonal recesses (Socket wrench, sockets). Hex keys are formed from a sin ...

socket wrench A socket wrench (or socket spanner) is a type of spanner (or wrench in North American English) that uses a closed ''socket'' format, rather than a typical open wrench/spanner to turn a fastener, typically in the form of a nut or bolt. The most ...

, or flathead screwdriver. Blind hole mounting variants may have tool slots on the same side as the pin. Federndes_Druckstück_2.tif, Spring plunger, cylindrical pin with rounded tip Federndes_Druckstück_3.tif, Ball plunger

Materials

At high temperatures or when the parts are exposed to aggressive chemicals, plastic balls or balls made of

corrosion-resistant Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion enginee ...

materials such as

silicon nitride Silicon nitride is a chemical compound of the elements silicon and nitrogen. (''Trisilicon tetranitride'') is the most thermodynamically stable and commercially important of the silicon nitrides, and the term ″''Silicon nitride''″ commonly re ...

can be used. The threaded sleeve is then typically made of

stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...

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 (for example, to adjust the angle of an exercise bench), and may have an integrated operating lever that is pushed in (''push pin plungers'') or a lever that is pulled out to manipulate the object (''pull pin plunger''). Similar principles are used in spring-loaded valves and valve stems(including

safety valves Safety is the state of being protected from harm or other danger. Safety can also refer to risk management, the control of recognized hazards in order to achieve an acceptable level of risk. Meanings The word 'safety' entered the English la ...

), or automatic ejectors on firearms.

Mechanics

Spring plungers can be used, for example, to lock levers in different positions. Spring-loaded plungers with anti-twist protection enable screwless fastening. Schalthebelarretierung.tif, Spring plungers used to lock a lever Knebel1_(fcm).jpg, Square

with a spring-loaded ball plunger to hold the socket Water_level_1.png, Mechanical levels can often be adjusted with spring-loaded set screws

Electronics

pogo pin A pogo pin or spring-loaded pin is a type of electrical connector mechanism with spring plungers that is used in many modern electronic applications and in the electronics testing industry. They are used for their improved durability over other ...

is a type of

electrical Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...

connector mechanism widely used in modern electronics. Compared to other electrical connectors, they have better durability and are more resistant to mechanical shock and vibration.

Archery

In modern

archery Archery is the sport, practice, or skill of using a Bow and arrow, bow to shooting, shoot arrows.Paterson ''Encyclopaedia of Archery'' p. 17 The word comes from the Latin ''arcus'', meaning bow. Historically, archery has been used for hunting ...

, an archery plunger allows the

arrow An arrow is a fin-stabilized projectile launched by a bow. A typical arrow usually consists of a long, stiff, straight shaft with a weighty (and usually sharp and pointed) arrowhead attached to the front end, multiple fin-like stabilizers c ...

to be deflected as it is fired from the bow.{{Cite web , title=Olympic Archery Explained: The Plunger , url=https://lancasterarchery.com/blogs/news-1/olympic-archery-explained-the-plunger , access-date=2024-12-26 , language=en It allows for adjusting the arrow's relative position on the arrow rest. By adjusting the stiffness and position of the plunger, the arrow can be adjusted to fly with the best possible flight, so that it travels straight.

References

Fasteners Mechanical fasteners