Shim
From Wikipedia, the free encyclopedia
- For the hill Shim in the Book of Mormon, see Cumorah.
In engineering, a shim is a thin and often tapered or wedged 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. The term comes from a Kentish word of unknown origin, dating to at least as early as 1723, meaning "a slip of wood." Originally a piece of iron fitted to a plow for scraping soil; meaning "thin slip to fill up a space or raise a level" is from 1860. The verb meaning "to wedge up a surface by means of a shim" is attested from 1937.
[edit] Shim materials
Many materials make suitable shim stock, 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 shims, but shims are often created ad hoc from whatever material is immediately available.
[edit] Shim: example usage
Examples of the usage of shim from different engineering disciplines are outlined below:
[edit] Aerospace engineering
Shims are widely used in Aerospace components to fill up extra spaces and it is used in different ways.
[edit] Automotive engineering
In automotive engineering 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 clearances. Clearance is adjusted by changing the thickness of the shim.
[edit] Carpentry
In carpentry or joinery small pieces of wood may be used to align gaps between larger timbers.
[edit] Fantasy
A drug harvested by refining fairy dust as extracted from enslaved fairies who are on mind-control drugs. Shim is an upper, with similar properties to drugs such as cocaine or ecstasy, and has the physical appearance of a pile of glitter. Shim has various side affects including swelling of knees, a taste of marshmellows on the back of the tongue, curling of straight hair and memory loss. Shim also can evoke musical feelings and spontaneously make a person burst out in song or melody.
[edit] Fencing
Thin pieces of metal called shims test that epee tips conform to specifications. If the shim can be inserted into the narrow gap of the weapon tip, the gap is the correct size. Saber has a similar set of shims used to determine whether or not the blade is correct thickness. Foil tips were initially tested with shims as well, but this was abandoned as being useless.
[edit] Lock picking
A small metal device used to quickly open a lock is called a shim. How to make a shim for picking pad locks
[edit] Luthiery
In luthiery shims made of various materials are often used to adjust neck alignment.
[edit] Masonry
In masonry small stones may be used to align or fill gaps between larger bricks or slabs.
[edit] Motorcycle maintenance
In the Robert M. Pirsig novel Zen and the Art of Motorcycle Maintenance one narrator discusses the use of a piece of beer can, as a shim, to tighten the handlebars.
[edit] Nuclear magnetic resonance / Magnetic resonance imaging
In NMR or MRI, "shimming" is used prior to the operation of the magnet to eliminate inhomogeneities in its field.
Initially magnetic field inside an MR scanner is far from being homogeneous. It could be even 100 times worse with respect to its homogeneity than an "ideal" field of the scanner. This is a result of the production tolerances and magnetic field of the "environment" - iron constructions in walls and floor of the examination room get magnetized and disturb the field of the scanner.
There are two types of shimming: active, and passive. The active shimming is done using coils with adjustable current. The passive shimming involves pieces of steel with good magnetic qualities. The steel is placed in the neighbourhood of the permanent or superconducting magnet. It gets magnetized and produces its own magnetic field. Additional magnetic field (produced by coils or steel) adds to the magnetic field of the magnet in such a way that the total field is getting more homogeneous.
[edit] Plumbing
In plumbing shims of metal align pipes.
[edit] Web design and computing
In web design a well known hack or kludge is to use a single-pixel transparent GIF as a shim to align spaces between tables in HTML to ensure a desired page layout. See spacer GIF.
In software engineering or hypermedia a piece of code (such as an API shim), placed between layers after the manner of a physical shim, in order to create a better fit or a smoother flow of code execution across layers.
In computer networking, a piece of extra code inserted between existing layers of the protocol stack to translate a communications protocol as the data is passed between the layers.
See also CPU shim for shims used to protect the core of CPUs from damage.
[edit] Tank (Vessel) levelling
When installing vessels over load cells, it is necessary to have a levelled surface. Thin metal plates (shims) are used for this purpose
[edit] Other Meanings
A shim may also refer to a transsexual, meaning a she and a him
Many people use the term "shim" in a colloquial sense which as a noun means "a collection of things" or "stuff", i.e. "Look at all that shim on the table.
As an adjective, shim can also be used to describe an unpleasant situation, person, place or thing, i.e. "Have you seen that movie? It was so shim.
Other expressions containing the word shim:
Shim vibes
Shim specfic
Shimest
shim-ba
Some variations on shim include:
Chum
Chim
Bim
Bih
Shimmy
[edit] Sources
- Byrnes, Joe. "To the Point; A Brief History of the Shim." American Fencing Summer 2006: 16.
- Howard, Michael. "Faery beasts and mythical animals" Summerset : Capall Bann, c2005.
www.dictionary.com
A shim is a small piece of wood used in construction to put on drywall and trim. http://www.shimcoshims.com/images/products/GS-1040-4-lrg.jpghttp://www.shimcoshims.com/images/products/GS-1040-4-lrg.jpg.
