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a machine part mounted under a nut or bolt head. Plain washers (Figure 1, a) are used to increase the load distribution where the load-bearing surface is uneven or of a soft material, where the bolt hole is elongated, or where the hole diameter is enlarged. Bevel washers (Figure l,b) and spherical washers (Figure 1, c) are used to prevent the nut or bolt head from warping during tightening. Open, or C, washers (Figure 1, d) are quick-release types used in fixtures to save time in removing a used part and mounting a new one. Packing washers made of a soft material
are mounted under the heads of threaded plugs to provide a hermetic seal. Spring lock washers (Figure l,e) reduce the likelihood that a bolt or nut will loosen since the elastic force of the compressed washer acts on the connection. Tab lock washers have sections that can be bent (Figure 1, f) to prevent a nut or bolt from turning with respect to a load-bearing shaft or other part. End plates (Figure 1, g) prevent axial displacement of parts mounted on a shaft (such parts may be held fixed or rotate on the shaft).