Common tightening methods for hexagonal bolts

1. Torque control method:

- Manual torque wrench: Set the torque value according to bolt specs and preload needs. For M10 hex bolts in general industrial equipment with medium tightness requirements, 30 - 50N·m might be set. Operators turn it until a "click" sound indicates the set torque is reached. Suitable for low-precision preload scenarios like mechanical housing fixing and furniture assembly.

- Electric torque wrench: Used in large-scale production or high-precision scenarios like auto manufacturing lines. It's pre-programmed for accurate torque output. For example, cylinder head bolts in cars need ±5% torque accuracy, which it can achieve. It's efficient and ensures consistent tightening quality.

2. Angle control method:

First tighten to a starting torque to close gaps, then rotate the bolt 90° - 120° for final tightening. Good for high-strength bolt connections in steel structures of large bridges or heavy machinery where large forces are involved.

3. Marking method: 

Mark the bolt head and connector. Tighten preliminarily to misalign marks, then continue until they align again. Simple but low-precision, for simple and low-preload scenarios like farm tool assembly or temporary brackets.

4. Hydraulic stretching method: 

For large bolts (diameter over 50mm) in big structures like ships and offshore platforms. A hydraulic tensioner elongates the bolt, and preload is controlled by calculating the elongation. For ship main engine anchor bolts, it ensures reliable and uniform connections.