Fastener replacement

When selecting and installing replacement fasteners, keep the following points in mind:

When replacing fasteners, use only identical bolts, washers, and nuts; they should be the same size, strength, and finish as originally specified.

When replacing graded (or metric class) bolts and capscrews, use only fasteners that have the manufacturer trademark or identification on the bolt head; do not use substandard bolts.

When using nuts with bolts, use a grade (or class) of nut that matches the bolt.

When installing nonflanged fasteners, use hardened steel flat washers under the bolt (capscrew) head and under the hex nut or locknut.

For bolts 4 inches (100 mm) or less in length, make sure that at least 11/2 threads and no more than 5/8-inch (16 mm) bolt length extends through the nut after it has been tightened. For bolts longer than 4 inches (100 mm), allow a minimum of 11/2 threads and a maximum of 3/4-inch (19 mm) bolt length protrusion.

Never hammer or screw bolts into place. Align the holes of the mating components so that the fastener surfaces are flush with the washers, and the washers are flush with the clamped surfaces.

When installing fasteners into threaded aluminum or plastic components, start the fasteners by hand to ensure that cross-threading does not damage the threads.

Do not use lock washers (split or toothed) next to aluminum surfaces.

When installing studs that do not have an interference fit, install them with thread locking compound.

When installing components mounted on studs, use free-spinning (nonlocking) nuts and helical spring (split) lock washers or internal-tooth lock washers. Avoid using locknuts because they tend to loosen the studs during removal. Do not use flat washers.

Do not use lock washers and flat washers in combination (against each other); each defeats the other’s purpose.

Use stainless steel fasteners against chrome plating, unpainted aluminum, or stainless steel.

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