screw

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screw,

simple machinemachine,
arrangement of moving and stationary mechanical parts used to perform some useful work or to provide transportation. From a historical perspective, many of the first machines were the result of human efforts to improve war-making capabilities; the term engineer
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 consisting essentially of a solid cylinder, usually of metal, around which an inclined planeinclined plane,
simple machine, consisting of a sloping surface, whose purpose is to reduce the force that must be applied to raise a load. To raise a body vertically a force must be applied that is equal to the weight of the body, i.e.
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 winds spirally, either clockwise or counterclockwise. It is used to fasten one object to another, to lift a heavy object, or to move an object by a precise amount. The ridge forming the inclined plane is called the thread; in cross section the ridge may be approximately triangular, square, or rounded. The vertical distance from any point on one thread to a corresponding point on the next successive thread is called the pitch. A thread can also be placed on the inner surface of a hollow cylinder. Two screws of the same pitch and diameter, one on the outer surface of a solid cylinder and the other on the inner surface of a hollow cylinder, can be arranged so that one may be driven spirally into the other, as in the common nut and bolt. The thread on the surface of the bolt is called the external, or male, screw; that on the inner surface of the nut, the internal, or female, screw. The common jackscrew used to lift automobiles, houses, and other heavy objects is an application of this principle. The internal screw is situated in the base, the external screw on a metal cylinder; at the top of the cylinder a lever or handle is fastened. As the handle is rotated, the external screw moves up the internal screw and the object placed on top of the jack is lifted. The mechanical advantage of the jackscrew, as of any other screw, is theoretically the ratio between the circumference through which the end of the handle moves and the pitch of the screw. Since, however, there is much friction in the operation of a screw, the amount of workwork,
in physics and mechanics, transfer of energy by a force acting to displace a body. Work is equal to the product of the force and the distance through which it produces movement.
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 put into this machine is much greater than the amount done and the efficiency is small. On the other hand, the small effort necessary to turn the handle, when compared to the enormous load raised, makes such a device of great value. The screw is often used for making delicate adjustments of tools and machines, e.g., in the micrometer screw and in the carburetor of the gasoline engine (for regulating the flow of gasoline). The self-tapping screw has notches in the first few threads that can cut female threads in a hollow cylinder. Wood and metal screws, the carpenter's and machinist's vise, the propeller of a boat or airplane, Archimedes' screw, and many other devices are applications of the screw.

Screw

 

a machine part of cylindrical—sometimes conical—shape, with a helical surface; or a part with helical blades. Screws are grouped as follows: screws that interact directly with an external, or working, medium, and screws that interact with a threaded opening of another part. The first group includes screws used for the production of rotary motion from moving gases and liquids (for example, in a wind engine); for the production of a tractive force (for example, an airplane propeller or a screw propeller on a ship); and for moving gases, liquids, and viscous, friable, or lump materials, sometimes with the creation in them of pressure and agitation (for example, in fans, pumps, screw conveyors, screw presses, and stirring screw conveyors). The second group includes motion screws, heavy-duty (force) screws, micrometer screws, fastening screws, and set screws.

A motion screw is the basic part of the screw mechanism in lathes and machines used for the rectilinear movement of assemblies and components (supports, tables, and so on) along a set of guides. Motion screws generally have a trapezoidal thread shape—less frequently square, triangular, or special—for screwing on nuts.

A heavy-duty force screw is a main part of a screw mechanism designed to produce large axial stresses in presses, furnace pushers, jacks (load-lifting screws), and so on. Force screws generally have a trapezoidal or buttress thread, less frequently a square thread. Short force screws, such as those in jacks, work by compression; they are checked for strength and buckling during their design and manufacture. Long force screws work by tension and are tested for tensile strength.

Micrometer screws have a precision thread with a small pitch; they are used in measuring machines, devices, and instruments (for example, in micrometers).

A fastening screw is a basic part of a detachable screw joint; the body of the screw has a threaded shaft at one end and a head at the other end. Fastening screws for metals and other solid materials usually have a triangular cylindrical thread. Noncritical small-diameter (to 8 mm) fastening screws are also made as self-tapping screws, with a tapered portion of partially shaped thread on the point. This type of screw extrudes the thread (in soft metals) or cuts it (in plastics and hard metals) when screwed into a smooth hole. Wood screws, which are used for fastening wooden parts, have a tapered portion of the thread at the point. The screw head serves both as a clamp for the parts to be joined and as a grip for tightening the screw with a screwdriver, wrench, or other tool. Standard fastening screws with hexagonal, square, and other types of heads are widespread.

Setscrews are generally used for the precise clamping of geodetic and other types of instruments, as well as for fastening screws in screw joints. Setscrews differ in the shape of the head and the clamping (adjusting) point.

N. IA. NIBERG

What does it mean when you dream about a screw?

The dreamer may feel as if they are being turned like a screw in a situation where someone is taking advantage of them.

screw

[skrü]
(design engineering)
A cylindrical body with a helical groove cut into its surface.
A fastener with continuous ribs on a cylindrical or conical shank and a slotted, recessed, flat, or rounded head. Also known as screw fastener.

screw

screw: nomenclature
An externally threaded fastener.

screw

1. a device used for fastening materials together, consisting of a threaded and usually tapered shank that has a slotted head by which it may be rotated so as to cut its own thread as it bores through the material
2. a threaded cylindrical rod that engages with a similarly threaded cylindrical hole; bolt
3. a thread in a cylindrical hole corresponding with that on the bolt or screw with which it is designed to engage
4. Billiards snooker
a. a stroke in which the cue ball recoils or moves backward after striking the object ball, made by striking the cue ball below its centre
b. the motion resulting from this stroke
5. another name for propeller
6. Slang an old, unsound, or worthless horse

screw

(jargon)
(MIT) A lose, usually in software. Especially used for user-visible misbehaviour caused by a bug or misfeature. This use has become quite widespread outside MIT.
References in periodicals archive ?
Wardle continued to lead until the final 800 yards when Hepples turned the screw.
Scotland trailed after Roger Warren's fifth-minute penalty but slowly turned the screw thanks to Chris Paterson, who finished with 13 points.
Despite being on New Hartley soil, Denton turned the screw when it mattered and produced a 3-2 success.
Caerws then turned the screw when Howells found himself unmarked and placed his header into the net.
ENGLAND Under-19s were today staring defeat in the face as Australia turned the screw at Riverside in their bid to square the series at 1-1 in the final match of three.
Kenny Irons hit the third goal in the 36th minute and Huddersfield further turned the screw just two minutes into the second half when substitute Rob Edwards crossed for Stewart to coolly finish.
Record readers have turned the screw on drug pushers with more calls flooding into our Shop A Dealer hotline.
And although O'Connor gave Ulster a lifeline with a penalty, Cardiff turned the screw with Xavier Rush charging through for his side's second try.
But Ballyoran turned the screw in the second-half and Paul McDonald gave them some breathing space with a great volley at the back post.
Cheishvili's men went ahead through Kvirikashvili's seventh-minute penalty and kept the pressure firmly on as their forwards turned the screw.
IG spokesman Jeremy Scott said: "Buyers of England runs were out in force and Pietersen's fifth-wicket stand with Colling wood really turned the screw with one client buying pounds 200 of fall of fifth-wicket runs at 385.
The visitors turned the screw after the break and in 66 minutes Chris Boyle's free-kick was met perfectly by Jim Smith but his powerful header was well saved by Brown.