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ข่าวบริษัท เกี่ยวกับ How to Understand Fastener Preload & Tightening Torque

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How to Understand Fastener Preload & Tightening Torque

2026-10-28

Fastener preload and tightening torque are critical factors to guarantee stable connection performance of bolts, screws and studs. Improper torque setting may cause loose joints, thread slipping or bolt fracture under working load.

What is Preload?

Preload is the tensile force applied to a fastener when it is tightened. It presses the connected components together, prevents separation under vibration, shear force or thermal expansion. For most structural fasteners, appropriate preload can greatly extend service life.

Tightening Torque Basics

Tightening torque refers to the rotational force used to turn nuts or screw heads. It is affected by many variables:

  • Thread friction and surface lubrication
  • Surface coating: galvanized, HDG, black oxide, passivation
  • Material hardness of bolts and mating parts
  • Thread tolerance and cleanliness

Common Mistakes in Torque Control

  1. Over-tightening: Excessive torque leads to bolt yielding or breaking.
  2. Under-tightening: Insufficient preload causes loosening under vibration, which often appears in automotive, machinery and construction equipment.
  3. Ignoring lubrication: Lubricants reduce friction, the same torque value will create much higher preload.

Tips for Selection & Installation

  • Refer to corresponding standards such as ISO, DIN, ASTM for recommended torque values.
  • Use calibrated torque wrenches for important assembly.
  • Do not reuse bolts that have reached yield point after heavy loading.

If you have inquiries about torque requirement for your fastener project, feel free to contact our technical team for customized suggestions.

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ข่าวบริษัท เกี่ยวกับ-How to Understand Fastener Preload & Tightening Torque

How to Understand Fastener Preload & Tightening Torque

2026-10-28

Fastener preload and tightening torque are critical factors to guarantee stable connection performance of bolts, screws and studs. Improper torque setting may cause loose joints, thread slipping or bolt fracture under working load.

What is Preload?

Preload is the tensile force applied to a fastener when it is tightened. It presses the connected components together, prevents separation under vibration, shear force or thermal expansion. For most structural fasteners, appropriate preload can greatly extend service life.

Tightening Torque Basics

Tightening torque refers to the rotational force used to turn nuts or screw heads. It is affected by many variables:

  • Thread friction and surface lubrication
  • Surface coating: galvanized, HDG, black oxide, passivation
  • Material hardness of bolts and mating parts
  • Thread tolerance and cleanliness

Common Mistakes in Torque Control

  1. Over-tightening: Excessive torque leads to bolt yielding or breaking.
  2. Under-tightening: Insufficient preload causes loosening under vibration, which often appears in automotive, machinery and construction equipment.
  3. Ignoring lubrication: Lubricants reduce friction, the same torque value will create much higher preload.

Tips for Selection & Installation

  • Refer to corresponding standards such as ISO, DIN, ASTM for recommended torque values.
  • Use calibrated torque wrenches for important assembly.
  • Do not reuse bolts that have reached yield point after heavy loading.

If you have inquiries about torque requirement for your fastener project, feel free to contact our technical team for customized suggestions.