The crane hook is one of the most critical load-bearing components in lifting operations. Any crack, wear, deformation, or corrosion can lead to serious safety risks. Regular inspection is essential to ensure safe and reliable crane operation.

1. Use a 20x Magnifier for Crack Inspection

Cracks are often difficult to detect with the naked eye, especially in the curved section of the hook body. A 20x magnifying glass should be used for regular inspection.

Invisible cracks do not mean the hook is safe. By the time damage becomes visible to the naked eye, the hook may already be close to failure.

2. Scrap the Hook Immediately if Wear Reaches 5%

A wear level of 5% or more is the absolute rejection limit. There is no acceptable margin once this threshold is exceeded.

When hook wear exceeds 5% of the original dimension, internal stress rises sharply and the risk of fracture increases significantly.

3. Always Measure with a Caliper

Hook opening dimensions must be measured precisely with a caliper—never judged by experience or visual estimation.

For hook sizes 006 to 5, verify the opening dimension a2. If the opening has increased by 15% compared with the original size, the hook must be scrapped.

For other hook models, measure the length value y. If it exceeds the original dimension by 10%, the hook must be scrapped.

4. Scrap the Hook if Twist Deformation Exceeds 10°

Twist deformation indicates that the internal metal structure has already suffered permanent damage.

If hook twist deformation exceeds 10 degrees, the hook must be scrapped immediately. Attempting to bend it back by force will only worsen internal cracking and may cause sudden failure during the next lifting operation.

5. Scrap the Hook if Shank Corrosion Reaches 5% or Threads Are Corroded

Grinding does not solve the problem—it can make corrosion even more severe and increase hidden risks.

If corrosion on the hook shank diameter d1 exceeds 5% of the original dimension, or if the threads show corrosion, the hook must be scrapped immediately.

Expert Reminder: Commonly Overlooked Areas

Some of the most neglected inspection points include:

• Apply grease regularly to the hook neck area
• Open the assembly when necessary to inspect bearing wear

These hidden areas are often overlooked, yet they are critical to maintaining long-term hook safety and performance.