A shim is a thin and often tapered or

wedge A wedge is a triangular shaped tool, and is 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 converti ...

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 can be bought commercially, for example as

laminated Lamination is the technique/process of manufacturing a material in multiple layers, so that the composite material achieves improved strength, stability, sound insulation, appearance, or other properties from the use of the differing materia ...

shims, but shims are often created

ad hoc Ad hoc is a Latin phrase meaning literally 'to this'. In English, it typically signifies a solution for a specific purpose, problem, or task rather than a generalized solution adaptable to collateral instances. (Compare with ''a priori''.) Com ...

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 ...

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

Applications

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

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

tappet A tappet is most commonly a component in an internal combustion engine which converts the rotating motion of the camshaft into linear motion of the valves, either directly or indirectly. An earlier use of the term was for part of the valve gear ...

s 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 slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...

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, manufacturing, manufactured object, system, or service; # other measured values (such as t ...

. On machinery 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 energy. Pumps can be classified into three major groups according to the method they ...

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 g ...

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, ships, timber bridges, concrete formwork, etc. Carpenters tr ...

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

timber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, wi ...

s. In

masonry Masonry is the building of structures from individual units, which are often laid in and bound together by mortar; the term ''masonry'' can also refer to the units themselves. The common materials of masonry construction are bricks, building ...

, small stones may be used to align or fill gaps between larger bricks or slabs. In

luthiery A luthier ( ; AmE also ) is a craftsperson who builds or repairs string instruments that have a neck and a sound box. The word "luthier" is originally French and comes from the French word for lute. The term was originally used for makers of ...

, a thin strip of various materials (most often steel or wood) can be used beneath the

nut Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edible fruits or seeds * Nut (hardware), fastener used with a bolt Nut or Nuts may also refer to: Arts, entertainment, and media Co ...

or the

saddle The 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 kno ...

of a

stringed instrument String instruments, stringed instruments, or chordophones are musical instruments that produce sound from vibrating strings when a performer plays or sounds the strings in some manner. Musicians play some string instruments by plucking the st ...

(such as a

guitar The guitar is a fretted musical instrument that typically has six strings. It is usually held flat against the player's body and played by strumming or plucking the strings with the dominant hand, while simultaneously pressing selected stri ...

mandolin A mandolin ( it, mandolino ; literally "small mandola") is a stringed musical instrument in the lute family and is generally plucked with a pick. It most commonly has four courses of doubled strings tuned in unison, thus giving a total of 8 ...

ukulele The ukulele ( ; from haw, ukulele , approximately ), also called Uke, is a member of the lute family of instruments of Portuguese origin and popularized in Hawaii. It generally employs four nylon strings. The tone and volume of the instrumen ...

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 usually made of plastic, or occasionally animal skin. Early forms of the instrument were fashi ...

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

neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...

, the angle of the neck can be adjusted by shimming. On some models a strip of

sanding paper upright=1.35, Sheets of sandpaper with different grit sizes (40 (coarse), 80, 150, 240, 600 (fine)). Sandpaper and glasspaper are names used for a type of coated abrasive that consists of sheets of paper or cloth with abrasive material glued to ...

was routinely inserted during final adjustment at the factory. Guitarists have often used strips cut from business cards,

credit cards A credit card is a payment card issued to users (cardholders) to enable the cardholder to pay a merchant for goods and services based on the cardholder's accrued debt (i.e., promise to the card issuer to pay them for the amounts plus the o ...

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

hardwood Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...

precision wedges for that purpose. On

printed circuit boards A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich struc ...

, 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 electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...

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 dissipated away from the device, th ...

. In

nuclear magnetic resonance spectroscopy Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fiel ...

, "'' 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. "Shimming an NMR Magnet", http://gtfg4.chem.upenn.edu/nmrsite/nmrdw/pdf%20files/Shimming.pdf

References

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Materials

Applications

References

Further reading