What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
At present, the commonly used fastener loosening prevention methods generally include non-removable anti-loosening solutions and friction-increasing anti-loosening solutions. The non-removable anti-loosening scheme uses welding, bonding or punch point riveting to change the detachable threaded connection into a non-detachable threaded connection. In the non-removable anti-loosening scheme, the threaded fasteners cannot be reused and the operation is troublesome. It is often used in some important occasions that require high anti-loosening performance without disassembly. The anti-loosening scheme that increases the frictional force uses the method of increasing the frictional force of the bolt (screw) head and the end face of the nut to achieve the purpose of anti-loosening. The anti-loosening solution that increases friction is not limited by space and can be disassembled repeatedly, but the reliability is poor. After a certain period of work, the anti-loosening effect will be reduced due to vibration and other reasons.
The maximum unscrewing torque of the lock nut is affected by many factors. For the research on the low-cycle fatigue performance of the lock nut, the pitch diameter of the thread, the helix angle and the bevel angle of the thread remain unchanged. Only the maximum elastic restoring force FNmax and the equivalent friction angle ρe of the thread piece will appear to a certain extent after repeated use. Change. Therefore, it is only necessary to analyze the variation law of the maximum unscrewing moment when the lock nut is subjected to cyclic load from these two aspects.
Washers are divided into: flat washer-C, large washer-A and C, extra large washer-C, small washer-A, flat washer-A, flat washer-chamfer-A, steel structure high Strength washer, spherical washer, cone washer, square bevel washer for I-beam, square bevel washer for channel steel, standard spring washer, light spring washer, heavy spring washer, internal tooth lock washer, internal serrated lock washer, External tooth lock washer, external tooth lock washer, single ear stop washer, double ear stop washer, outer tongue stop washer, stop washer for round nut.
Bolt: A type of fastener consisting of a head and a screw (a cylinder with an external thread), which needs to be matched with a nut to fasten and connect two parts with through holes. This form of connection is called a bolted connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is a detachable connection. [1] Stud: A type of fastener that has no head and only has external threads on both ends. When connecting, one end of it must be screwed into the part with the internal threaded hole, the other end must pass through the part with the through hole, and then the nut must be screwed on, even if the two parts are tightly connected as a whole. This form of connection is called a stud connection, which is also a detachable connection. It is mainly used for occasions where one of the connected parts is thick, requires a compact structure, or is not suitable for bolt connection due to frequent disassembly. [1] Screw: It is also a type of fastener consisting of a head and a screw. It can be divided into three categories according to the purpose: machine screws, set screws and special-purpose screws. Machine screws are mainly used for a fastened connection between a part with a fixed threaded hole and a part with a through hole, without the need for nut matching (this connection form is called screw connection, which is also a detachable connection; it can also be Cooperate with the nut, it is used for the fast connection between two parts with through holes.) The set screw is mainly used to fix the relative position between the two parts. Special purpose screws, such as eyebolts, are used for hoisting parts. [1] Nuts: with internal threaded holes, generally in the shape of a flat hexagonal column, but also in a flat square column or flat cylindrical shape, with bolts, studs or machine screws, used to fasten and connect two parts, make it a whole. [1] 5. Self-tapping screw: Similar to machine screw, but the thread on the screw is a special thread for self-tapping screw. It is used to fasten and connect two thin metal components to make them a whole. Small holes need to be made in advance on the components. Due to the high hardness of this kind of screw, it can be directly screwed into the hole of the component, so that the Forming a corresponding internal thread [1] 6. Wood screw: It is also similar to a machine screw, but the thread on the screw is a special thread for wood screws, which can be directly screwed into wooden components (or parts) to connect a band through The metal (or non-metallic) part of the hole is fastened to a wooden member. This connection is also a detachable connection. [1] 7. Washers: A type of fastener with an oblate annular shape. It is placed between the supporting surface of the bolt, screw or nut and the surface of the connecting part, which increases the contact surface area of the connected parts, reduces the pressure per unit area and protects the surface of the connected parts from damage; another type of elastic washer, It can also play a role in preventing the nut from loosening. [1] 8. Retaining ring: It is installed in the shaft groove or shaft hole groove of the machine and equipment, and plays the role of preventing the parts on the shaft or the hole from moving left and right. [1] 9. Pins: mainly used for positioning the left and right parts, and some are also used for connecting parts, fixing parts, transmitting power or locking fasteners. [1] 10. Rivet: A type of fastener consisting of a head and a shank, which is used to fasten and connect two parts (or components) with holes to make them a whole. This form of connection is called rivet connection, or riveting for short. It is a non-removable link. Because if the two parts joined together are separated, the rivets on the parts must be broken. [1] 11. Components and connection pairs: Assemblies are a type of fasteners supplied in combination, such as a combination of a certain machine screw (or bolt, self-supplied screw) and a flat washer (or spring washer, lock washer); Connection pair refers to a type of fastener that is supplied by a combination of special bolts, nuts and washers, such as high-strength hexagon head bolt connection pairs for steel structures. [1] 12. Welding nail: a heterogeneous fastener composed of a nail rod and a nail head (or no nail head), which is fixed to a part (or component) by welding, so as to be connected with other parts. .
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