Bolt torque is the rotational force applied to a bolt to achieve proper clamping force. It ensures the bolt creates sufficient tension to hold the joint together securely.

Proof load is the maximum load a bolt can withstand without permanent deformation. It's typically 70-90% of the bolt's yield strength and is used to determine safe working loads.

Bolt Torque Calculator

Q: Why is proper torque important?

Proper torque ensures joint integrity, prevents bolt failure, maintains safety, and ensures optimal performance. Under-torquing can cause loose joints, while over-torquing can damage the bolt or joint.

Q: What affects torque values?

Bolt size, material strength, thread pitch, friction coefficient, lubrication, surface finish, and environmental conditions all affect torque values. These factors determine the relationship between applied torque and achieved clamping force.

Bolt Parameters

Bolt Size

Metric bolt size

Bolt Class

Bolt strength class

Thread Pitch

Thread pitch in millimeters

Friction Coefficient

Friction coefficient (0.1-0.3)

Proof Load (%)

Percentage of proof load (50-90%)

Calculation Results

Bolt Torque Calculator: Your Guide to Proper Bolt Tightening

Proper bolt torque is crucial for joint integrity and safety. Our Bolt Torque Calculator helps you determine the correct torque value for your specific bolt application.

Understanding Bolt Torque Requirements

Bolt torque calculations are important for several reasons:

Safety: Prevents joint failure and accidents
Performance: Ensures proper load distribution
Reliability: Maintains joint integrity
Longevity: Prevents premature failure
Compliance: Meets industry standards

How to Use the Bolt Torque Calculator

Select Bolt Size: Choose the appropriate metric bolt size
Select Bolt Class: Choose the bolt strength class
Enter Thread Pitch: Select the thread pitch
Enter Friction Coefficient: Input the friction coefficient
Enter Proof Load: Specify the proof load percentage
Click Calculate: Get torque values

Bolt Torque Calculation Formula

Torque Formula:
T = K × F × d
Where:
T = Torque (N⋅m)
K = Torque coefficient (0.15-0.3)
F = Axial force (N)
d = Nominal bolt diameter (mm)

Axial Force Formula:
F = σ × A × (P/100)
Where:
σ = Yield strength (MPa)
A = Tensile stress area (mm²)
P = Proof load percentage

Common Bolt Classes and Properties

Class 8.8:
- Yield Strength: 640 MPa
- Tensile Strength: 800 MPa
- Typical Use: General purpose
Class 10.9:
- Yield Strength: 900 MPa
- Tensile Strength: 1000 MPa
- Typical Use: High-strength applications
Class 12.9:
- Yield Strength: 1080 MPa
- Tensile Strength: 1200 MPa
- Typical Use: Critical applications

Real-World Examples

Example 1: M10 Class 8.8 Bolt

Bolt Size: M10
Bolt Class: 8.8
Thread Pitch: 1.5 mm
Friction Coefficient: 0.15
Proof Load: 75%
Results:
- Torque: 47 N⋅m
- Axial Force: 31.4 kN
- Clamp Force: 23.6 kN
- Status: Acceptable

Example 2: M16 Class 10.9 Bolt

Bolt Size: M16
Bolt Class: 10.9
Thread Pitch: 2.0 mm
Friction Coefficient: 0.15
Proof Load: 75%
Results:
- Torque: 192 N⋅m
- Axial Force: 128 kN
- Clamp Force: 96 kN
- Status: Acceptable

Frequently Asked Questions

What is bolt torque?

The rotational force applied to a bolt to achieve proper clamping force.

Why is proper torque important?

It ensures proper joint integrity and prevents bolt failure.

What is proof load?

The maximum load a bolt can withstand without permanent deformation.

How do I measure torque?

Use a calibrated torque wrench and follow the manufacturer's specifications.

What affects torque values?

Bolt size, material, thread pitch, friction, and lubrication.