Bolt is a type of fastener consisting of a head and a screw (a cylinder with external threads). A bolt must fit with a nut to securely connect two parts with through-holes
The connection form connected by the bolt and nut is called bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a detachable connection.
Bolts can be classified according to six aspects, such as the force mode of connection, head shape, length, tooth type performance grade and production accuracy.The details include:
1.Bolts are divided into ordinary ones and those with hinged holes according to the force mode of connection.
2.Bolt according to the head shape: hexagonal head, round head square head, countersunk head and so on. Hex head bolts, called hex bolts for short, are the most commonly used.
3.According to the length of the thread is divided into full thread and non-full thread two types.
4.According to the thread of the tooth type is divided into coarse teeth and fine teeth two types, rough teeth in the mark of the bolt is not shown.
5. Bolts can be 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. The bolts above 8.8 (including 8.8) are made of low carbon alloy steel or medium carbon steel and have been heat treated (quenching + tempering), generally known as high strength bolts. Class 8.8 bolts (excluding Class 8.8) are commonly called ordinary bolts.
6.According to the production accuracy of ordinary bolts can be divided into A, B, C three grades, A, B for refined bolts, C for coarse bolts.
In addition, bolt detection methods are divided into manual and machine two kinds. Manual is the most primitive and most commonly used consistent detection method. In order to minimize the outflow of defective products, general production enterprise personnel visually inspect the packaged or delivered products to eliminate defective products (including tooth damage, mixing, rust, etc.).
The other way is the machine automatic detection, mainly magnetic particle detection. Magnetic particle detection is to use the interaction between the magnetic leakage field and the magnetic powder at the defect of the bolt, aiming at the possible defects of the bolt (such as cracks, slag inclusion, mixing, etc.) and the difference in the permeability of steel, the magnetic field at the discontinuous of these materials will change after magnetization.
Forming part of the magnetic flux leakage workpiece surface generated leakage magnetic field, so as to attract magnetic powder to form a defect of magnetic powder accumulation – magnetic marks, under the appropriate lighting conditions, showing the position and shape of the defect, the accumulation of these magnetic powder to observe and explain, has achieved the purpose of eliminating defective products.
Post time: Dec-13-2022