A shim is a thin and often tapered or

wedge A wedge is a triangle, triangular shaped tool, a portable inclined plane, and one of the six simple machines. It can be used to separate two objects or portions of an object, lift up an object, or hold an object in place. It functions by conver ...

d piece of material, used to fill small gaps or spaces between objects. Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear.

Materials

Many materials make suitable shim stock (also often styled shimstock), or base material, depending on the context: wood, stone, plastic, metal, or even paper (e.g., when used under a table leg to level the table surface). High quality shim stock such as laminated shims can be bought commercially, but shims are often created

ad hoc ''Ad hoc'' is a List of Latin phrases, Latin phrase meaning literally for this. In English language, English, it typically signifies a solution designed for a specific purpose, problem, or task rather than a Generalization, generalized solution ...

from whatever material is immediately available. Laminated shim stock is stacked

foil Foil may refer to: Materials * Foil (metal), a quite thin sheet of metal, usually manufactured with a rolling mill machine * Metal leaf, a very thin sheet of decorative metal * Aluminium foil, a type of wrapping for food * Tin foil, metal foil ma ...

that can be peeled off one layer at a time to adjust the thickness of the shim.

Applications

automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...

s, shims are commonly used to adjust the clearance or space between two parts. For example, shims are inserted into or under bucket tappets to control

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or Slurry, slurries) by opening, closing, or partially obstructing various passageways. Valves are technically Pip ...

clearances. Clearance is adjusted by changing the thickness of the shim. In assembly and weld fixtures precision metal shims are used between two parts so that the final production parts are created within the product drawing's specified

tolerances Engineering tolerance is the permissible limit or limits of variation in: # a physical dimension; # a measured value or physical property of a material, manufactured object, system, or service; # other measured values (such as temperature, hu ...

. On

machinery A machine is a physical system that uses power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolec ...

installations (

pumps A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic or pneumatic energy. Mechanical pumps serve in a wide range of applications such ...

motor An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gene ...

s, etc.) the recommended practice requires shims under every equipment support foot. This guarantees a flexibility for adjustments, like a slight raising or lowering of a motor, when parts of the machinery need to be replaced. In

carpentry Carpentry is a skilled trade and a craft in which the primary work performed is the cutting, shaping and installation of building materials during the construction of buildings, Shipbuilding, ships, timber bridges, concrete formwork, etc. C ...

, small pieces of wood may be used to align gaps between larger

timber Lumber is wood that has been processed into uniform and useful sizes (dimensional lumber), including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, window frames). ...

s. In

masonry Masonry is the craft of building a structure with brick, stone, or similar material, including mortar plastering which are often laid in, bound, and pasted together by mortar (masonry), mortar. The term ''masonry'' can also refer to the buildin ...

, small stones may be used to align or fill gaps between larger bricks or slabs. In luthiery, a thin strip of various materials (most often steel or wood) can be used beneath the nut or the

saddle A saddle is a supportive structure for a rider of an animal, fastened to an animal's back by a girth. The most common type is equestrian. However, specialized saddles have been created for oxen, camels and other animals. It is not know ...

of a

stringed instrument In musical instrument classification, string instruments, or chordophones, are musical instruments that produce sound from vibrating strings when a performer strums, plucks, strikes or sounds the strings in varying manners. Musicians play so ...

(such as a

guitar The guitar is a stringed musical instrument that is usually fretted (with Fretless guitar, some exceptions) and typically has six or Twelve-string guitar, twelve strings. It is usually held flat against the player's body and played by strumming ...

mandolin A mandolin (, ; literally "small mandola") is a Chordophone, stringed musical instrument in the lute family and is generally Plucked string instrument, plucked with a plectrum, pick. It most commonly has four Course (music), courses of doubled St ...

ukulele The ukulele ( ; ); also called a uke (informally), is a member of the lute (ancient guitar) family of instruments. The ukulele is of Portuguese origin and was popularized in Hawaii. The tone and volume of the instrument vary with size and con ...

banjo The banjo is a stringed instrument with a thin membrane stretched over a frame or cavity to form a resonator. The membrane is typically circular, and in modern forms is usually made of plastic, where early membranes were made of animal skin. ...

) to raise the height of either. On guitars with a bolt-on or screwed-on

neck The neck is the part of the body in many vertebrates that connects the head to the torso. It supports the weight of the head and protects the nerves that transmit sensory and motor information between the brain and the rest of the body. Addition ...

, the angle of the neck can be adjusted by shimming. On some models a strip of sanding paper was routinely inserted during final adjustment at the factory. Guitarists have often used strips cut from

business card Business cards are card stock, cards bearing business information about a company or individual. They are shared during formal introductions as a convenience and a memory aid. A business card typically includes the giver's name, types of co ...

s, credit cards or picks as shim material, while luthiery supply stores have started to sell specialized

hardwood Hardwood is wood from Flowering plant, angiosperm trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal ecosystem, boreal latitudes they are mostly deciduous, but in tropics and subtropics mostl ...

precision wedges for that purpose. On

printed circuit boards A printed circuit board (PCB), also called printed wiring board (PWB), is a laminated sandwich structure of conductive and insulating layers, each with a pattern of traces, planes and other features (similar to wires on a flat surface) ...

, special CPU shims are used to protect the

central processing unit A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary Processor (computing), processor in a given computer. Its electronic circuitry executes Instruction (computing), instructions ...

when installing a

heat sink A heat sink (also commonly spelled heatsink) is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is thermal management (electronics), ...

. In

nuclear magnetic resonance spectroscopy Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a Spectroscopy, spectroscopic technique based on re-orientation of Atomic nucleus, atomic nuclei with non-zero nuclear sp ...

, "'' shimming'' an NMR magnet" is a procedure to generate homogeneous magnetic field along the sample volume to obtain pure Lorentzian line shapes of various resonances in the spectrum. This is accomplished by manual shimming of individual shims, or automatic shimming procedure. In crew rowing, shims (also called "spacers" or "height washers") are used to adjust the position of the oarlock to match the rower.

References

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Materials

Applications

References

Further reading