Precision lock nuts main types and features in detail
Different types of lock nuts can be distinguished from the structural characteristics, anti-loosening principle, advantages, limitations and typical applications of five aspects, the following is a specific analysis.
1. R-type radial Precision lock nuts
Structural features: the main body is round, one end of the radial with 3 locking screw holes, some models correspond to the position of the axial groove (depth of about 1/3 of the height of the nut), adaptable to hexagon socket head cap screws.
Principle of anti-loosening: first screw the nut to the preset position, and then tighten the radial locking screw, so that the end of the screw extrudes the outer threads of the bolt or forces the nut wall at the groove to deform inward, forming a threaded vice interference fit, eliminating the gap with the help of radial pressure and generating friction torque to prevent loosening.
Advantage: Reliable anti-loosening effect, the anti-loosening torque after locking can reach 80% of the initial pre-tightening torque; the locking screw can be adjusted to realize the second tightening, suitable for frequent adjustment of the position of the scene.
Limitations: radial force may lead to local deformation of the bolt, especially for fine threads; long term use is easy to wear threads, not suitable for high frequency vibration or shock load conditions.
Typical applications: machine tool spindle bearing positioning, ball screw end fixing, precision instrument shaft locking.
2. F-type teeth belly Precision lock nuts
Structure features: the use of special teeth, nut threads belly processing 3 ° - 5 ° micro-angle of inclination, and the standard bolt threads belly to form a wedge-shaped engagement, the shape of most of the hexagonal or round head.
Anti-loosening principle: when tightening, the wedge-shaped structure of the nut threads and the bolt threads closely fit, resulting in axial wedge force, increasing the positive pressure on the threads, so that the friction torque is 30%-50% higher than that of ordinary nuts; when vibration, the wedge-shaped structure automatically compensates for the gap with the change of the load, to maintain the tightness of the mesh.
Advantages: no additional locking parts, simple structure, installation and dismantling is the same as ordinary nuts; uniform thread force, no damage to the bolt, suitable for high-frequency vibration and high-speed rotation scenarios.
Limitations: high requirements for thread processing accuracy, tooth shape error ≤ 0.01mm, the cost is slightly higher than ordinary nuts; preload is not enough to reduce the anti-loosening effect.
Typical applications: automobile engine block connection, rail transportation bogie parts, vibrating screen bearing seat fixing.
3. K-type axial Precision lock nuts
Structural features: one end of the integrated elastic washer (mostly butterfly or wave-shaped, and the nut molded in one piece), or the bottom of the processing of axial elasticity of the claw piece, the main body is often hexagonal or flange design.
Principle of anti-loosening: During the tightening process, the elastic washer or claw piece is compressed to generate axial elasticity, which continuously exerts preload on the threaded sub, offsetting the preload decay caused by vibration or temperature changes; flange-face models can be used to assist in anti-loosening by increasing friction on the contact surface.
Advantage: easy installation, no need for additional washers; uniform axial elasticity, no damage to the bolt, reusable, fatigue life of elastic parts ≥ 50 disassemblies.
Limitations: elastic washers are easy to fail under ≥150℃ high temperature environment for a long time; limited axial elasticity, not suitable for heavy load or large gap occasions.
Typical applications: fixing of motors of household appliances, connection of cylinders of pneumatic components, locking of guide rails and slides of light mechanical equipment.
4. Rn square Precision lock nuts
Structure features: square shape, side length is usually 10%-20% larger than the same specifications of the hexagonal nut; the inner threads can be combined with radial locking (such as radial screw holes) or axial elasticity (such as the bottom of the anti-slip teeth), square side to facilitate the wrench clamping.
Anti-loosening principle: In addition to relying on its own locking structure (e.g. radial screws, anti-slip teeth), the square shape creates an additional anti-rotation torque by adhering to the plane of the device, forming a double anti-loosening guarantee.
Advantages: good clamping stability, especially in the case of small space and limited wrench operation; large contact surface of the square shape, suitable for heavy-duty connections that require anti-rotation.
Limitations: Large size, not suitable for lightweight or compact structures; square corners are easy to bump, need to reserve space when installing.
Typical applications: heavy machine tool table fixing, construction machinery bracket connection, mold guide pillar end locking.
Through the comparison of these five aspects, the characteristics of different types of locknuts can be clearly distinguished, so that it is easy to choose according to the actual working conditions of the type of load, installation space and maintenance requirements.
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