# Production strategies

Production strategies can be divided into three main categories:

- Tightening within torque limits: this is the easiest tightening method, it is enough applying torque within the limits.

  Torque vs. Time

  A | Upper torque limit | B | Nominal
  C | Lower torque limit |  |

- Tightening within torque and angle limits: this is a more reliable way to tighten, because an additional information (angle) is used during the tightening process.

  Torque vs. Angle

  A | Upper torque limit | B | Nominal
  C | Lower torque limit | D | Lower angle limit
  E | Upper angle limit |  |

  Using this method, it is possible to detect potential problems on the joint (refer to the following examples):

Torque is correct, but angle is too small: Misalignment problem The hole is not completely threaded (or it is not deep enough) The bolt is stopped by oil in a dead hole There is dirt in the threads The threads are damaged The screw is already tightened |
Angle is correct, but torque is too low: The thread may be stripped out The screw is too soft (tightened over yield) Unexpected low µ (friction coefficient) |

- Tightening with torque and additional angle rotation (torque + angle): the bolt is first tightened to a certain torque and then it is further tightened to a specific angle. The goal is to stress the bolt over the yield point. Even with differences in the angle, the torque (causing clamping force) is quite reliable. Sometimes the joint is specially designed and the analysis of the joint helps making sure that strain is far away from the breaking point.

  Torque vs. Angle

- Tightening to elastic limits (yield) : The bolt is tightened until its elastic limit is reached. This method is used when each bolt must achieve the maximum clamping force. This method is seldom used in the car industry (example: Connecting rods). It is more common in the aerospace industry.

Torque vs. Angle

| These bolts are normally used in special applications and the shank of the bolt is designed with a special thin section to be stretched (this bolt works as a precise spring).

In this Section

- Torque
- Torque (Control) / Angle (Monitor)
- Torque (Monitor) / Angle (Control)
- Torque (Control) / Angle (control) OR
- Torque (Control) / Angle (control) AND
- Torque (Control) / Prevailing Torque (Monitor)
- Loose
- Yield Point