The Rivet That Wasn’t Setting Properly: Rivet Gun Setup, Not the Rivets
A pneumatic rivet gun setting blind rivets. The rivets weren’t flaring properly — some were loose, some were over-set. The customer thought the rivets were defective. The rivets were fine. The gun wasn’t adjusted. This is about rivet gun setup, not about the fasteners.
How a blind rivet sets
A blind rivet has a mandrel (pin) inside a hollow body. The gun pulls the mandrel. As the mandrel pulls, it flares the body on the back side. When the mandrel reaches its break point, it snaps. The rivet is set. If the pull force is too low, the body doesn’t flare (loose rivet). If it’s too high, the body crushes (over-set). The gun’s pull force and stroke must match the rivet size.
The rivet sizes and settings
| Rivet size | Grip range | Pull force needed | Gun setting |
|---|---|---|---|
| 3.2 mm | 1-5 mm | 5000 N | Low power |
| 4.0 mm | 1-7 mm | 7000 N | Medium power |
| 4.8 mm | 1-10 mm | 10000 N | High power |
| 6.4 mm | 2-18 mm | 18000 N | Max power |
What we found
The gun was set to high power (for 4.8 mm rivets) but the customer was using 3.2 mm rivets. The pull force was 10000 N on a rivet that needs 5000 N. The rivet body crushed before the mandrel broke. The rivet was loose (over-set). We adjusted the gun to low power. The rivets set properly.
What we did
1. Matched the gun to the rivet. We set the gun’s pull force to match the rivet size. For 3.2 mm rivets, low power. For 4.8 mm, high power. The rivet flares correctly.
2. Checked the nosepiece. The nosepiece (the tip that pulls the mandrel) must match the rivet size. A 4.8 mm nosepiece on a 3.2 mm rivet doesn’t grip the mandrel properly. We changed to the correct nosepiece.
3. Checked the air pressure. The gun needs 6 bar. The plant air was 4 bar. The pull force was low. The rivets didn’t set. We set the regulator to 6 bar. The gun pulls correctly.
4. Trained the operator. The operator held the gun at an angle. The gun must be perpendicular to the surface. A tilted gun doesn’t pull straight. The rivet flares unevenly. We trained the operator to hold the gun square.
The rivet rule: If rivets aren’t setting, check the gun. Match the pull force to the rivet size. Use the correct nosepiece. Set the air pressure to 6 bar. Hold the gun perpendicular. The rivets that weren’t setting weren’t defective — the gun was wrong for the size.
