What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
In each maintenance, the newly replaced stud bolts and other accessories should be inspected. During the inspection, the focus should be on the head and guide part of the stud bolt. It is also necessary to strictly check that each part of the thread has No cracks or dents, also check the tooth shape of the studs for changes. Is there any abnormality in the thread pitch? If there is any abnormality, it must not be used again. A torque wrench should be used when installing the connecting rod cover. It must be tightened according to the specified standards, the torque should not be too large or too small, and attention should be paid to selecting the stud bolts and studs of the supporting manufacturer.
1. For low strength (below 500 N/mm2 or below 60000 psi) bolts use general soft steel, generally use SAE 1008 or JIS SWRM 8 (or SWRCH 8). 2. Lower strength (600 N/mm2 or 74000 psi) ) bolts use general soft steel, but limited carbon content grade, generally use SAE 1010 - 1015 or JIS SWRM 10 - 15 (or SWRCH 10 - 15). .3. Higher strength ( 800 N/mm2 or 125000 psi ) bolts of medium carbon steel, low carbon boron steel plus quenching and tempering, generally use SAE 1035 - 1040 or SWRCH 35K - 40K. 4. High strength (900 N/mm2 or more or 150000 psi or more) bolts use medium carbon Alloy steel or low carbon boron steel, in terms of application, if the metric Class 10.9 uses low carbon boron steel, the imprint should be added under the series imprint to become 10.9, and the imprint of the inch 8.2 grade is also used with the general Grade 8 bolts The imprint is different for easy identification. High-strength bolts made of low carbon boron steel cannot be used in high temperature conditions. The design strength exceeds Class 12.9 or ASTM A574 ultra-high strength bolts are limited to medium carbon alloy steel plus quenching and tempering. The performance grades of bolts for steel structure connection are divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Among them, the bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and are heat-treated (quenching, tempering), commonly known as high-strength bolts, the rest are commonly known as ordinary bolts. The bolt performance grade label consists of two parts of numbers, which represent the nominal tensile strength value and yield ratio of the bolt material respectively. For example, a bolt with a performance level of 4.6 means: 1. The nominal tensile strength of the bolt material is 400MPa; 2. The yield ratio of the bolt material is 0.6; 3. The nominal yield strength of the bolt material is 400×0.6=240Mpa . Performance level 10.9 high-strength bolts, after heat treatment, can achieve: 1. The nominal tensile strength of the bolt material is 1000MPa; 2. The yield ratio of the bolt material is 0.9; High-strength bolts, processing and manufacturing problems are compared Small, general fastener manufacturing companies can master the manufacturing process; but problems are prone to occur in material selection and heat treatment. Material selection is the primary link. Various alloying elements have a great influence on the properties of the material, and the material must be subjected to spectral composition analysis; secondly, the fracture problem and the choice of heat treatment process have a great influence and are very important. Dealers and traders must control the inspection and performance testing links; automotive fasteners have high requirements and must carefully control the quality.
T-bolt is a common fastener, which is mostly used where there is a T-slot on the workbench or where the connection can only be made from the side to be connected. However, it has the following problems in the actual production and processing process. 1. The T-bolt manufactured according to the current GB37-88 is used in conjunction with the T-slot on the worktable, which is easy to damage the T-slot on the worktable. 2. According to the observation and investigation, it is found that 90% of the damage to the T-bolt manufactured by GB37-88 is thread damage during use, and the T-shaped part is rarely damaged, resulting in a waste of raw materials. SUMMARY OF THE INVENTION The purpose of the present invention is to solve the problem that the current composite T-bolt is easy to damage other equipment and cause waste of raw materials in the actual use process, and to provide a simple structure, easy to use, safe and reliable, and not easy to damage other equipment. , thereby saving raw materials and other advantages of composite T-bolts. In order to achieve the above purpose, the present invention adopts the following technical scheme: a composite T-bolt, which includes a bolt, and one end of the bolt is connected with the T-shaped block cockroach. The T-shaped block is provided with a tapered hole, and the connection between the bolt and the T-shaped block is a cone, which is matched with the tapered hole. The utility model combines the two parts of the T-shaped block and the threaded bolt through the T-shaped block and the taper hole and the cone on the bolt to automatically lock the two parts before use. When the threaded part of the bolt is damaged, only the threaded bolt needs to be replaced. That's it. Compared with the domestic T-shaped bolts currently produced in the manufacturing process, the utility model solves the problems of complicated manufacturing processes and waste of raw materials. It is well known that the manufacture of T-bolts requires processing such as forging, turning, milling, and heat treatment. Since the composite T-bolt is used in combination with the T-block and the bolt, and the T-block is rarely damaged, after purchasing or manufacturing the T-block once, you only need to purchase or manufacture the bolt in the future. Compared with the T-bolts currently produced in China, the composite T-bolts can better protect the T-slots on the working surface. Because the T-bolt currently produced in China will rotate a certain angle around the axis of the T-bolt when fixing the object, the T-bolt will rotate at a certain angle, thereby reducing the contact between the T-bolt T-shaped surface and the T-slot stress surface of the working face. surface, causing stress concentration on this surface. The composite T-bolt avoids the above problems due to the increase of the guide surface, thereby protecting the T-slot. The beneficial effects of the utility model are: 1. Saving raw materials. 2. Reduce processing costs. 3. Simplify the technological process. 4. Protect the T-slot.
Nuts are usually used in conjunction with bolts or screws to fasten other components and are a common and widely used component. In order to make the nut not easy to loosen and fall off when it is subjected to strong vibration and irregular strong toggling, the combined nut has appeared on the market.
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