Why Reusing Sheared or Stretched Bolts Is Bad Practice

It is tempting to put a sheared bolt back in the box, to reuse a bolt that was removed from a tight joint, or to straighten a bent fastener for another job. In most agricultural joints, that is a false economy. Bolts that have been loaded past their design have already given up some of their strength, and reusing them sets up the next failure.

A sheared bolt has done its job

A shear bolt that broke on overload sacrificed itself to protect a more expensive component. It cannot be reused, even if the remaining end looks undamaged. The material around the break has already been stressed beyond its limit. Replace it with a new shear bolt of the correct grade.

Stretched bolts lose clamping force

When a bolt is over-torqued, or used in a joint designed for torque-to-yield tightening, it stretches past its elastic limit. It may look fine, but it no longer clamps with the force it was designed for. A stretched bolt in a critical joint can snap later, even under normal load. When the manual says a bolt is one-use, replace it.

Bent bolts are not straightened

A bent bolt from an impact has work-hardened at the bend. Straightening it back does not restore its strength, and the bend point remains a stress raiser. Throw it away. A bent bolt may also have hidden cracks that open later under load.

Corroded and damaged bolts are replaced

Rusty bolts, bolts with damaged threads, or bolts that have been seized and heated apart are also discarded. Their threads no longer engage cleanly, and their strength may be compromised. The cost of a new bolt is tiny next to the cost of a failed joint in the field.

Keep the fastener box clean

After a repair, discard suspect bolts immediately rather than dropping them back into the drawer. Sort the box regularly and throw away bent, rusty or sheared parts. A clean drawer of known-good bolts keeps repairs safe, and nobody has to guess whether a fastener is still serviceable.

References

PATEL N, CHEN L. Reuse limits of loaded agricultural fasteners[J]. Biosystems Engineering, 2021, 203: 420-428.

Patel, N., and L. Chen. "Reuse Limits of Loaded Agricultural Fasteners." Biosystems Engineering, vol. 203, 2021, pp. 420-428.

Patel, N., & Chen, L. (2021). Reuse limits of loaded agricultural fasteners. Biosystems Engineering, 203, 420-428.