Generally speaking, bolt grip lengths should be

• A. Longer than the material
• B. Twice the thickness
• C. Equal to the thickness of the material which is fastened together
• D. Shorter than the material

Answer: (C)

The grip length is the portion of the bolt shank that sits inside the parts being fastened. The best practice is to set this length equal to the combined thickness of the materials being joined. That way, the bolt passes cleanly through all parts, the threaded portion can engage the nut properly, and the parts are clamped with the intended load. If the grip length is longer than the material, part of the bolt would extend beyond the far side, which can interfere with other components or require a longer nut or washers. If it’s too short, the bolt won’t pass through all the parts, so you can’t achieve proper clamping. By matching the grip length to the material thickness, you ensure reliable, correct assembly.