Frame Straightening

TB 9-2510-242-40

5-2

Frame Straightening

a. Temperature Conditions. Straighten the frame under ambient and uniform temperature conditions; that is, do

not apply any external heat. A non-uniform temperature within the section being straightened will create internal

stresses, result in a non-uniform bend back, and reduce the frame's strength.

b. Stresses/Stressing. Every bend in a frame or member is the result of the metal being stressed beyond its yield

strength. Therefore, to cold straighten a frame the metal is again stressed beyond its yield strength, but in the opposite

direction. When restored to its original shape the metal still retains its original characteristics. However, repeated

bending of the metal beyond yield strength will ultimately cause it to fail as a result of work hardening fatigue. Inspect

frame visually for local or overall damage using frame alignment methods in Section VI, Axle Alignment Procedure, and

frame drawings to ensure accuracy.

c. Inspection, A careful frame inspection will determine which members/segments are damaged, to what extent,

in which direction, and over what length. The results of the inspection are used to make a frame repair plan that, based

on the skill and experience of the repair personnel, outlines the sequence of the operations needed to repair a damaged

frame.

d. Application of Straightening Forces. To straighten a bent frame member, bend it back beyond its original

straight form to allow the metal to spring back to the original straight form. To avoid over-bending, the initial

straightening force applied should be only enough to bring the frame member back to its straight form. Remove the

force and measure the spring-back. Re-apply sufficient force to bend the member beyond "straight" by the amount of

measured spring-back. Remove the force and check the member for straightness. Repeat this procedure as necessary

until the bend has been eliminated and the member is in its original straight condition.

5-3

Frame Welding

a. Remove Structure Load. The first step to repair a weld joint is to remove the structural load from members,

member segments and the joint requiring repair. Use jack stands or other cribbing to safely support both sides of the

damaged weld joint. Also place supports at other points to ensure that the frame and members cannot move when old

welds are removed.

b. Align Members. Position members of the damaged segment or joint for proper alignment or fit. Adjust or shim

jack stands and cribbage to obtain proper alignment of members or segments and to close cracks. Broken pieces of

segments shall touch each other. Measure and record type, size, and extent of each damaged weld that is to be

removed for repair.

c. Prepare Weld Joints/Crack. Remove old weld material from the welded joint or the crack. Where groove

welds are to be used, remove material to be replaced from members or segments. Use a portable grinder of suitable

size to make a bevel groove along the length of the