What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Drilling screw is a new invention of people in recent years. A screw is a common term for fasteners, an everyday colloquial language. The tail of the drill tail screw is in the shape of a drill tail or a pointed tail, and no auxiliary processing is required. Drilling, tapping and locking can be directly carried out on the setting material and basic material, which greatly saves construction time. Compared with ordinary screws, its toughness and pull-out force and maintenance force are high, and it will not loosen for a long time after combination. It is easy to use safe drilling and tapping in one operation. Drill tail screw Drill tail screw use: It is a kind of screw, mainly used in the fixing of color steel tiles of steel structures, and can also be used for thin plate fixing of simple buildings. It cannot be used for metal-to-metal bonding. Materials and models The materials are iron and stainless steel, of which stainless steel is divided into various materials. Models are: Φ4.2/ Φ4.8/ Φ5.5/ Φ6.3mm, the specific length can be agreed upon request. According to the different drill tails, it can be divided into: round head rice / cross / plum blossom, countersunk head (flat head) / rice seed / cross / plum blossom, hexagonal washer, round head washer (big flat head), horn head, etc.
According to the force of the connection, it is divided into ordinary and hinged holes. According to the shape of the head: there are hexagonal head, round head, square head, countersunk head and so on. Among them, the hexagonal head is the most commonly used. Generally, countersunk heads are used where connections are required. The English name of the riding bolt is U-bolt. It is a non-standard part. The shape is U-shaped, so it is also called a U-bolt. There are threads on both ends that can be combined with nuts. It is mainly used to fix tubular objects such as water pipes or sheets such as automobile plates. Springs are called riding bolts because of the way they fix things like a person rides a horse. According to the length of the thread, it is divided into two categories: full thread and non-full thread. According to the thread type, it is divided into two types: coarse thread and fine thread. The coarse thread type is not displayed in the bolt mark. The bolts are divided into eight grades: 3.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, and 12.9 according to their performance grades. Among them, the bolts above grade 8.8 (including grade 8.8) are made of low-carbon alloy steel or medium-carbon steel and are heat-treated (quenched). + Tempering), commonly known as high-strength bolts, and below grade 8.8 (excluding 8.8) are commonly known as ordinary bolts. Ordinary bolts can be divided into three grades: A, B, and C according to the production accuracy. Grades A and B are refined bolts, and grade C is rough bolts. For connecting bolts for steel structures, unless otherwise specified, they are generally ordinary rough grade C bolts. There are differences in the processing methods of different grades. Usually the corresponding processing methods are as follows: ① The bolts of grade A and B bolts are processed by lathes, with smooth surfaces and accurate dimensions. High, rarely used; ②C-grade bolts are made of unmachined round steel, the size is not accurate enough, and its material property grade is 4.6 or 4.8. The deformation is large during shear connection, but the installation is convenient and the production cost is low. It is mostly used for tensile connection or temporary fixation during installation.
High-strength hexagon head bolt combination screws for steel structures, mainly used in railway and highway bridges, boiler steel structures, industrial plants, high-rise civil buildings, tower and mast structures, hoisting machinery and their steel structures need to use friction-type high-strength bolt combinations for screws. It is characterized by an extra dodecagon at the end of the bolt, also known as the bolt. When installing, a special electric wrench must be used, which has two socket heads up and down, one is set on the hexagonal body of the nut, and the other is set on the decagon body of the outer hexagon screw. When tightening, apply a clockwise force to the nut, and apply an equal counterclockwise force to the dodecagon body of the bolt, so that the connecting neck between the end of the outer hexagon screw and the dodecagon body is subjected to torsion shearing until the neck is sheared. So far, the installation has come to an end. This torsion shear type high-strength outer hexagon screw is a one-time-use screw and generally cannot be removed after installation.
As one of the indispensable parts in automobiles, the main function of the screw is to fix the parts with through holes and the parts with screw holes together. The existing automobile screws include a screw rod and a head, and the thread pitches on the screw rod are equal. , When in use, directly screw the screw into the screw hole, so as to connect and fix the two parts, this connection method, however, when the screw has different thread spacing or part of the thread is damaged, the thread cannot be repaired and replaced. Then the whole screw will be scrapped.
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