Some Failures Caused in Installing Core-pulling Rivets

1.Pull-through: rivet core was pulled out in a whole, but the core fracture wasn’t broken yet, a hole left on the rivet nut after riveting. The causes can be summarized as the pulling force on the rivet core is too large, or mandrel cap diameter is too small, or rivet material is too soft, or rivet body hole surface is too lubricated.

2.Burr: after pull riveting, the fracture burr came out through the hole of rivet body, or the tip protruding formed rough burr. The reasons for the burrs are: the diameter of the mandrel cap is too small, the rivet body material is soft, the hole diameter of the workpiece is too large, the gun nozzle of the rivet gun is too large, the too large distance between the pinch core fracture and the mandrel cap exceeds riveting thickness.

3.Nail-head off: after pull riveting, the nail head couldn’t be inserted into the objects so fell off from rivet body. Nail head falls off because the mandrel cap diameter is too large, or the rivet body is much short that does not match with the riveting thickness.

4. Riveting body cracking: after pull-riveting, riveting body of blind rivet nuts occurs vertical break, or completely split. Reasons for cracking may be: the rivet body has too high hardness after annealing or without heat treatment; the size of the mandrel cap is too large; the harmful impurity contents in the material are too many or there has an interlayer.

5. Rivet stem pop-up or rivet body not plump-up: when in pull riveting, the rivet stem of blind rivets completely ejects, or rivet body is not fully inflated. The reason for this phenomenon is: when the rivet mandrel is being made, the pulling strength is too low; rivet body hardness is high (auneven nnealing); rivet mandrel in the electroplating process has occurred hydrogen embrittlement.

6. Rivet body loosed after riveting: after pull riveting, the rivet body of blind rivet nuts loosed in the workpiece hole. The main reasons are: the rivet stem tension is too low; workpiece drilling is too large; rivet body hardness is too high; the improper design for rivet clamping force.