The deflection angle of the thread fit and the softness […]
The deflection angle of the thread fit and the softness of stainless steel can easily cause the lock of the stainless steel screw
1. The fit of stainless steel screw and stainless steel nut belongs to clearance fit, and has their respective implementation international standard tolerance ranges. Therefore, the central axis of the internal and external threads are basically not on the same straight line when they are matched, and the contact surface of the internal and external threads should be reduced for inclination.
2. The uneven force or tilt during the locking process causes the center axis of the stainless steel screw and the stainless steel nut to maximize the tilt, so that the stainless steel screw and the stainless steel nut thread are not completely in contact with each other. The force or the force on each unit becomes greater.
3. The larger the deflection angle of the stainless steel screw and the stainless steel nut, the smaller the force-bearing area of the threaded fit, and the more likely to damage the tooth pattern.
4. Stainless steel screws are softer than carbon steel screws. If the iron chips are rubbed off during the locking process, they will stick and not fall, which will interfere with the smooth in and out of the threads and cause the bottom of the tooth to die on the top of the tooth.
Excessive locking force and low thermal conductivity of stainless steel can easily lead to thread locking
1. When locking the stainless steel nut, the torque (locking force) must be greater than the friction force of the stainless steel screw and the stainless steel nut itself before the nut can be turned. When the nut rotates and descends along the thread line, the stainless steel screw will be stretched due to the reaction force. When the torque (locking force) exceeds the screw's yield point (safe torque), the screw will have residual strain and maintain the extended state . When the screw stretches beyond its elastic range, it will produce permanent deformation and cause the thread to lock up.
2. During the rotation of the screw and nut, heat is generated due to friction, and the thermal conductivity of stainless steel is relatively low. When the generated pressure and heat destroy the chromium oxide layer (the oxide layer that stainless steel is not easy to rust), the metal tooth pattern will occur directly Clogging, coupled with the softness of stainless steel, leads to adhesion. The greater the locking force, the greater the heat generated, and the easier it is for the stainless steel in the shank of the screw to produce adhesion.
The solution to the locking of stainless steel screws In response to the above-mentioned reasons that are prone to locking, the use of stainless steel screws requires as much attention as possible:
1. Keep the center axis of the stainless steel screw and the stainless steel nut perpendicular to the locked surface to reduce the deflection angle.
2. Use a torque wrench or socket wrench as much as possible to avoid excessive force and control the torque within the safe torque range.
3. Try to use a manual wrench to slow down the locking speed, keep the threads clean, use lubricating oil to reduce the coefficient of friction, reduce heat energy, and thus reduce adhesion.
4. Choose relatively high hardness products to reduce thread shearing.
5. The use of stainless steel anti-locking agent has a significant effect on reducing the lock-up ratio.