What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The capped nut can prevent the bolt connection from directly contacting with the outside world, which is corroded and makes it difficult to disassemble later. Nuts with caps in the prior art are mostly of one-piece structure, and the surface is not treated with anti-oxidation, which is easy to be corroded. In addition to the protective effect, the fastening method is the same as that of ordinary nuts, so it is easy to loosen when subjected to severe vibration. .
Common fastening screws include self-tapping screws, fine-pitch drywall screws, traditional wood screws, and fiberboard screws. The following are the characteristics of commonly used screws, everyone should choose them reasonably. Self-tapping screws The correct application of self-tapping screws should be used for the fastening and connection of metal materials with pre-drilled holes. It has the function of automatically tapping out the internal thread on the metal body, and can complete the thread engagement with it to play a tightening role. However, due to its high thread bottom diameter, when it is used in wood products, the cut into the wood will be shallower; and because the thread pitch is small, there is less wood structure between every two threads. Therefore, it is unreliable and unsafe to use self-tapping screws for wood mountings, especially loose wood. Drywall Screws The proper use of fine-pitch drywall screws is for fastening and joining between metal studs and plasterboard. It suffers from similar drawbacks as self-tapping screws when used on wood mountings. Moreover, due to the large diameter of the head of the dry-wall screw, the embedding of the head is poor, and it is easy to cause unevenness between the head of the screw and the surface of the mounting part after installation. Traditional wood screws Before using traditional wood screws, pre-drilling holes are required on the wooden mounting parts, otherwise it is easy to cause wood cracking. In addition, since the traditional wood screws are not heat-treated, the use of electric tools can easily cause the groove shape to be damaged, and manual installation is very laborious. Fiberboard screws are relatively new types of wood screws, suitable for power tool installation. However, due to its relatively simple thread design, it still cannot effectively solve the stubborn problem of easy cracking when used on hardwood, and it does not have any advantages in screwing speed and screwing torque. [2]
Self-tapping screws, or quick-thread screws, are quick-release fasteners made of steel that are galvanized and passivated on the surface. Self-tapping screws are mostly used for the connection between thin metal plates (steel plates, saw plates, etc.). When connecting, first make a threaded bottom hole for the connected piece, and then screw the self-tapping screw into the threaded bottom hole of the connected piece.
The first person to describe the spiral was the Greek scientist Archimedes (c. 287 BC - 212 BC). An Archimedes screw is a huge spiral contained in a wooden cylinder that is used to irrigate fields by raising water from one level to another. The real inventor may not be Archimedes himself. Maybe he was just describing something that already existed. It may have been designed by the skilled craftsmen of ancient Egypt for irrigation on both sides of the Nile. In the Middle Ages, carpenters used wooden or metal nails to attach furniture to wooden structures. In the 16th century, nail makers began producing nails with a helical thread, which were used to connect things more securely. That's a small step from these kinds of nails to screws. Around 1550 AD, the metal nuts and bolts that first appeared in Europe as fasteners were all made by hand on a simple wooden lathe. Screwdrivers (screw chisels) appeared in London around 1780. Carpenters have found that tightening a screw with a screwdriver holds things in place better than hitting with a hammer, especially with fine-grained screws. In 1797, Maudsley invented the all-metal precision screw lathe in London. The following year, Wilkinson built a nut and bolt making machine in the United States. Both machines produce universal nuts and bolts. Screws were quite popular as fixings because an inexpensive method of production had been found at that time. In 1836, Henry M. Philips applied for a patent for a screw with a cross recessed head, which marked a major advance in screw base technology. Unlike traditional slotted head screws, Phillips head screws have the edge of the head of the Phillips head screw. This design makes the screwdriver self-centered and not easy to slip out, so it is very popular. Universal nuts and bolts can connect metal parts together, so by the 19th century, the wood used to make machines to build houses could be replaced by metal bolts and nuts. Now the function of the screw is mainly to connect the two workpieces together and play the role of fastening. The screw is used in general equipment, such as mobile phones, computers, automobiles, bicycles, various machine tools and equipment, and almost all machines. need to use screws. Screws are indispensable industrial necessities in daily life: extremely small screws used in cameras, glasses, clocks, electronics, etc.; general screws for televisions, electrical products, musical instruments, furniture, etc.
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