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Chì ci hè u viti

Time: 2020-07-10 Comment: 41

A screw, or bolt, is a type of fastener, typically made of metal, and characterized by a helical ridge, known as a male thread (external thread) or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as a female thread (internal thread), often in the form of a nut or an object that has the internal thread formed into it. Other screw threads are designed to cut a helical groove in a softer material as the screw is inserted. The most common uses of  Screws  are to hold objects together and to position objects.

Un fucile guasgi sempre una testa nantu à un'estremità chì cuntene una forma apposta chì permette à ellu di esse vultiscia, o cundotta, cù una strumenta. L'utili cumuni per e vitture di vittura includenu tornaviti è chjavi. A testa hè di solitu più grande chì u corpu di u viti, chì mantene a vitezza da esse cundotta più in fondu di a lunghezza di a vite è da furnisce una superficie di cuscinetto. Ci sò eccezzioni; per esempiu, Bulloni di carru have a domed head that is not designed to be driven; set screws often have a head smaller than the outer diameter of the screw; J- Bolts  have a J-shaped head which is not designed to be driven, but rather is usually sunk into concrete allowing it to be used as an anchor bolt. The cylindrical portion of the screw from the underside of the head to the tip is known as the shank; it may be fully threaded or partially threaded.[1] The distance between each thread is called the "pitch".

The majority of screws are tightened by clockwise rotation, which is termed a right-hand thread; a common mnemonic device for remembering this when working with screws or bolts is "righty-tighty, lefty-loosey." Screws with left-hand threads are used in exceptional cases. For example, when the screw will be subject to counterclockwise torque (which would work to undo a right-hand thread), a left-hand-threaded screw would be an appropriate choice. The left side pedal of a bicycle has a left-hand thread.

More generally, screw may mean any helical device, such as a clamp, a micrometer, a ship's propeller or an Archimedes' screw water pump.


Differenziazione trà u bolt è u viti
Un bullone in carru cù noce quadrata
Un bullone strutturale cù una rondella esagonale è una rondella.

There is no universally accepted distinction between a screw and a bolt. A simple distinction that is often true, although not always, is that a bolt passes through a substrate and takes a nut on the other side, whereas a screw takes no nut because it threads directly into the substrate. Machinery's Handbook describes the distinction as follows:

Un bullone hè un filettatore filettatu esternamente cuncepitu per l'inserzione attraversu i buchi in parti assemblati, è hè normalmente intenzatu à esse strettu o liberatu da u torcamentu di un dado. Un viti hè un filettatore filettatu esternamente capace d'esse inseritu in i buchi in parti assemblati, di accoppiare cù un filu internu preformatu o di furmà u so filu, è di esse strettu o liberatu da torcia a testa. Un fastener filettatu esternamente chì ùn hè impeditu di esse vultatu durante l'assemblea è chì pò esse strettu o liberatu solu da torcia una noce hè un bolt. (Esempiu: Bolti di Testa Rotonda, Pista Bolti, bulloni di aratu.) Un fermu filettatu esternamente chì hà forma di filu chì pruibisce l'assemblea cun un dado chì hà un filu drittu di a lunghezza di passaghju multipla hè un vite. (Esempiu: Viti di lignu, Viti di tapping.) [2]

Questa distinzione hè in cunfurmità cù ASME B18.2.1 è alcune definizioni di dizziunariu per viti [3] [4] è bolt. [5] [6] [7]

The issue of what is a screw and what is a bolt is not completely resolved with Machinery's Handbook distinction, however, because of confounding terms, the ambiguous nature of some parts of the distinction, and usage variations.[8][not in citation given] Some of these issues are discussed below:
Viti à Macchina

ASME standards specify a variety of "Machine Screws"[9] in diameters ranging up to 0.75 in (19.05 mm). These fasteners are often used with   Nuts  as well as driven into tapped holes. They might be considered a screw or a bolt based on the Machinery's Handbook distinction. In practice, they tend to be mostly available in smaller sizes and the smaller sizes are referred to as screws or less ambiguously as machine screws, although some kinds of machine screw can be referred to as stove bolts.
Viti hex cap

U standard ASME B18.2.1-1996 specifica Viti Hex Cap chì varienu in dimensioni da 0.25-3 in (6.35–76.20 mm) di diametru. Questi fasteners sò assai simili à Bulloni Hex. They differ mostly in that they are manufactured to tighter tolerances than the corresponding bolts. Machinery's Handbook refers parenthetically to these fasteners as "Finished Bulloni hex".[10] Reasonably, these fasteners might be referred to as bolts, but based on the US government document Distinguishing Bolts from Screws, the US government might classify them as screws because of the tighter tolerance.[11] In 1991 responding to an influx of counterfeit fasteners Congress passed PL 101-592[12] "Fastener Quality Act" This resulted in the rewriting of specifications by the ASME B18 committee. B18.2.1[13] was re-written and as a result they eliminated the "Finished Hex Bolts" and renamed them the "Hex Cap Screw"-a term that had existed in common usage long before, but was now also being codified as an official name for the ASME B18 standard.
Bulloni di lug e bolne di testa

These terms refer to fasteners that are designed to be threaded into a tapped hole that is in part of the assembly and so based on the Machinery's Handbook distinction they would be screws. Here common terms are at variance with Machinery's Handbook distinction.[14][15]
Viti Lag
Viti Lag, ancu chjamati bulloni lag
Una vista laterale

Viti Lag (ancu chjamati bulloni lag, anche se questu hè un misnomeru) sò basamente viti di legnu grandi. Viti à a testa quadrata è viti à testa hexale sò cuparti da i standard ASME B18.2.1, è u capu hè tipicamente un hex esterno. Un bullone tipico di lag pò varià in diametru da 1⁄4 in (6.35 mm) à 1 1⁄4 in (31.75 mm), è lunghe da 1⁄4 à 6 in (6.35 à 152.40 mm) o più, cù i fili grossi. di una forma di filu di legnu o di legnu in folla (ma più grande).

I materiali sò generalmente sustrato in acciaio di u carboniu cun un revestimentu di galvanizazione di zincu (per resistenza à a corrosione). U revestimentu di zincu pò esse luminoso (electroplated), giallu (electroplated), o gris grigiu dull hot-dip galvanizzati. E bulloni Lag sò aduprati per incuntrà l'infrastruzione di legnu, per rinfriscà i piedi di i macchinari à i pavimenti di legnu, è per altre applicazioni pesanti di carpinteria. L'aggittivu lag hè venutu da un adupratu iniziale principale di tali fasteners: l'aghjunzione di lags cum'è steli di canna è altre parti simili. [16]

These fasteners are "screws" according to the Machinery's Handbook criteria, and the obsolescent term "lag bolt" has been replaced by "lag screw" in the Handbook.[17] However, in the minds of many tradesmen, they are "bolts", simply because they are large, with hex or square heads. In the United Kingdom and Australia, lag screws are known as coach screws.
Normi ​​di u guvernu americanu

The US government made an effort to formalize the difference between a bolt and a screw because different tariffs apply to each.[18] The document seems to have no significant effect on common usage and does not eliminate the ambiguous nature of the distinction between screws and bolts for some threaded fasteners. The document also reflects (although it probably did not originate) significant confusion of terminology usage that differs between the legal/statutory/regulatory community and the fastener industry. The legal/statutory/regulatory wording uses the terms "coarse" and "fine" to refer to the tightness of the tolerance range, referring basically to "high-quality" or "low-quality", but this is a poor choice of terms, because those terms in the fastener industry have a different meaning (referring to the steepness of the helix's lead).
Quistione storica

I vechji standard USS è SAE definìanu e viti di tappe cum'è fermette cù filetti chì sò stati filettati à a testa è i bulloni in quantu di chjavi cù lastre chì eranu parzialmente senza fili. [19] A relazione di sta regula per l'idea chì un perno per definizione piglia una noce hè chjaru (perchè a sezione non roscata di u filu, chì hè chjamatu u grip, era prevista à passà da u substratu senza filettassi). Questu hè oghji una distinzione obsoleta.
Vocabulu cuntrullatu versus lingua naturale

The distinctions above are enforced in the controlled vocabulary of standards organizations. Nevertheless, there are sometimes differences between the controlled vocabulary and the natural language use of the words by machinists, auto mechanics and  Others . These differences reflect linguistic evolution shaped by the changing of technology over centuries. The words bolt and screw have both existed since before today's modern mix of fastener types existed, and the natural usage of those words has evolved retronymously in response to the technological change. (That is, the use of words as names for objects changes as the objects themselves change.) Non-threaded fasteners predominated until the advent of practical, inexpensive screw-cutting in the early 19th century. The basic meaning of the word screw has long involved the idea of a helical screw thread, but the Archimedes screw and the screw gimlet (like a corkscrew) preceded the fastener.

A parola bolt hè ancu una parolla assai antica, è hè stata usata di seculi per riferisce à bastone di metallu chì passavanu da u substratu per esse appiccicatu da l'altra parte, spessu per via di non-filettatu (clinching, forge welding, pinning, wedging, etc.). ). A cunnessione di questu sensu à u sensu di un perno di porta o di u bullone di ballesta hè apparente. In u 19u seculu, i bulloni appiccicati via i fili di viti sò stati spessu chjamati viti in cuntrastu per cuntrastà i viti.

In common usage, the distinction (not rigorous) is often that screws are smaller than bolts, and that screws are generally tapered while bolts are not. For example, cylinder head bolts are called "bolts" (at least in North American usage) despite the fact that by some definitions they ought to be called "screws". Their size and their similarity to a bolt that would take a nut seem linguistically to overrule any other factors in this natural word choice proclivity.
Altri distinzioni

Bolts have been defined as headed fasteners having external threads that meet an exacting, uniform bolt thread specification (such as ISO metric screw thread M, MJ, Unified Thread Standard UN, UNR, and UNJ) such that they can accept a non-tapered nut. Screws are then defined as headed, externally threaded fasteners that do not meet the above definition of bolts.[citation needed] These definitions of screw and bolt eliminate the ambiguity of the Machinery's handbook distinction. And it is for that reason, perhaps, that some people favor them. However, they are neither compliant with common usage of the two words nor are they compliant with formal specifications.

Una pussibile distinzione hè chì una vite hè pensata per taglià u so propiu filu; ùn hà micca bisognu d'accessu da o esposizione à u latu oppostu di u cumpunente affissatu. Sta definizione di viti hè ancu più rinfurzata da cunsiderazione di i sviluppi di vitture cume Tek Viti per rivestimenti di tetti, viti di autoforazione è di autofilettante per diverse applicazioni di fissaggio in metallu, viti di tettu per rinfurzà a cunnessione tra u tettu di u tettu è u rafter, viti per decking etc. D'altra parte, un bullone hè a parte maschile di un sistema di fissaghjulu cuncepitu per esse accettatu da un saccu pre-equipatu (o noce) di esattamente u listessu disegnu di filu.


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