In this method of locking a coiled spring, the washer is placed underneath the nut, as shown in Fig. such cases sometimes two nuts of equal thickness are used as shown in Fig. But as it required a special thin spanner to turn it, in practice, it is more usual to place the taking nut below the lock nut as shown in Fig. Theoretically, the lower nut, which is a lock nut, may be the thin nut, as shown in Fig. This makes the lower nut act as a lock nut. This cause the lower flanks of threads of the lower nut to come in contact with the upper flanks of the threads of the bolt, causing a wedging action between them. Now the upper nut is held by a spanner While the lower nut is pulled in the opposite direction. This virtually makes the upper nut take up all to load, While the lower nut to function simply as a washer since there will not be any contact between the threads of the bolt and the lower nut. When another nut is screwed down hard over the lower nut, it tends to pull the bolt through the lower nut. This method of locking of nut or bolt head is suitable when the nut or bolt head is placed near the vertical edge of the workpiece. You might like: Different Types of Springs and Their Applications #5 Locking By a Tab WasherĪ washer provided with a rectangular projection is called a tab washer. Since the nut is held tight within the grooves of the lock plate, the nut is prevented from slackening. The figure shows the assembly of the locking of a nut by the lock plate. The plate is fixed to the bearing surface by a tap bolt screwed into it. The plate is grooved so that the grooves in the plate receive the hexagonal corners of the nut at every 30° rotation. Initially, the nut is tightened, and then the lock plate is inserted through the nut. The empirical proportions of the lock plate are shown in the figure. This type of locking is employed in heavy engineering work, as in the case of connecting rods, wheel shafts, etc. The dowel pin screwed into the bearing surface prevents the rotation of the collar. When the bolt hole is not close to the vertical edge of the workpiece, this nut is used in conjunction with a separate collar, as shown in the figure. This locking method is possible if the bolt hole is close to the nearest vertical edge, as in the case of the marine engine connecting rods. The projecting dog end of the set screw enters the groove in the cylindrical portion of the nut and prevents the slackening of the nut. The split pin is then inserted in the hole, and the split ends of the pin are opened to prevent it from coming out while in use. After the nut has been finally tightened, a small hole is drilled through the blot close to the top face of the nut. The simplest method of locking a nut using a split pin is shown in the figure. In the friction method, an additional nut called a lock nut or a spring washer is used to lock the nut. The positive locking methods use a split pin, a screw, a lock plate, or a tab washer to lock the nut. However, the tendency of unscrewing is reduced if the threads of the nut and bolt are of a good fit.
The various locking devices for nuts are classified into positive and friction types. To prevent this, some means of locking the nut from unscrewing is necessary.
This consequently may result in a serious breakdown. Under such conditions, because of the working clearance existing between the mating threads, the nut develops a tendency to work loose or unscrew by itself. In addition, sometimes, they are required to carry varying axial loads also, for example, as the crossheads and connecting rods of an engine. The types of nuts and bolts used in the moving parts of machinery will be subjected to continuous vibration. When a nut is tightened over the bolt, a small working clearance exists between the threads of a nut and bolt, even in the highest class of fits.
#Multi nut how to#
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This nut can be easily operated by the thumb and a finger and is used where it must be adjusted frequently.
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