Why shear tab connections fail inspection
On site, everything looks tight.
But inspectors check one detail:
Thread protrusion.
If the nut bottoms out before clamping the joint, the connection is not actually tight.
It fails inspection.
What nut bottoming really means
Nut bottoming occurs when:
- Bolt threads run out inside the nut
- Nut hits the unthreaded shank or bolt end
- Clamping force stops increasing
- Installer thinks joint is tight but it is not
Why bolt length causes this
If bolt grip length is longer than the bolt’s threaded portion:
- Nut reaches the end of threads too early
- No further tightening is possible
- Joint remains loose internally
Common causes
1. Bolt length selected without considering grip length
2. Extra washers added on site
3. Variations in plate thickness
4. Fully threaded vs partially threaded confusion
What happens if ignored
- Connections fail inspection
- Load is not transferred properly
- Slippage occurs under load
- Rework and delays follow
How to prevent this
Calculate grip length properly
Ensure minimum 2 threads protrude beyond nut
Select partial or full thread appropriately
Avoid unnecessary washers
Verify protrusion during inspection
Final thought
A nut that stops turning is not always tight.
It may just be out of threads.