Did you know that it’s dangerous to re-use old frame bolts? Old bolts no longer have their rated strength and can fail under load. This can cause loose frame components that result in vibrations, cab and body damage and loss of vehicle control.

The problem is that threaded nut-and-bolt fasteners are designed to be tightened sufficiently to cause the bolts to stretch under tension. This provides clamping forces on the washers to keep the mounted components firmly together and resist any tendency of the nuts and bolts to rotate and loosen. When the nuts and bolts are removed, the bolts remain in the stretched condition and cannot be re-tightened without pulling them beyond their strength limits.

To avoid this problem, always replace old frame nuts and bolts with new ones of the same diameter and grade. Learn to read the grade marks cast on the head of the bolts. And always use washers on both sides to distribute the clamping load.
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This feature offers a variety of short tips and facts about apparatus maintenance and testing. Look for it every month. Submissions of 150 words or less are welcome from our readers, subject to editing. Send them to Senior Editor Chris Cavette at cavettes@ix.netcom.com.