Screw Torque Calculator
Calculate the optimal torque for screws and bolts to ensure proper fastening without material damage.
Safety Disclaimer: This calculator provides estimations only. Always refer to manufacturer specifications when available. Improper torque application may result in fastener failure, damage to materials, or safety hazards. When in doubt, consult a professional engineer.
Torque Calculation Results
Fastener Type:
Material:
Diameter: mm
Thread Pitch: mm
Grade/Class:
Lubrication State:
Recommended Torque:
N·m ( ft·lb)
Torque Range:
Note: Always refer to manufacturer specifications when available. These values are estimates based on general engineering principles.
About Our Screw Torque Calculator
Our Screw Torque Calculator is a precision tool designed to help engineers, mechanics, technicians, and DIY enthusiasts determine the optimal torque values for various fasteners. Applying the correct torque ensures that fasteners are tight enough to prevent loosening while avoiding damage to the fastener or substrate material.
Why Torque Matters
Proper torque application is critical for several reasons:
- Joint Integrity: Insufficient torque may lead to loose connections and joint failure
- Fastener Protection: Excessive torque can cause fastener stretching, thread stripping, or breakage
- Material Protection: Proper torque prevents damage to the materials being fastened
- Consistent Assembly: Specified torque values ensure consistency in assembly processes
- Safety: Correctly torqued fasteners are essential for structural integrity and safety in many applications
How Torque is Calculated
The calculator uses industry-standard formulas that take into account multiple factors:
- Fastener Diameter: Larger diameters generally require higher torque
- Thread Pitch: The distance between adjacent threads affects the torque requirement
- Material: Different materials have different strength characteristics
- Grade/Class: Higher grades indicate stronger fasteners that can withstand higher torque
- Lubrication: Reduces friction and can significantly affect required torque
- Friction Coefficient: Varies based on material and surface finish
The basic formula for calculating torque is:
T = K × D × F
Where:
- T is the torque
- K is the nut factor (determined by friction, thread geometry, and lubrication)
- D is the nominal bolt diameter
- F is the clamping force (typically 75-85% of the bolt's yield strength)
How to Use Our Calculator:
- Select the fastener type from the dropdown menu
- Choose the material of the fastener
- Enter the diameter in millimeters
- Specify the thread pitch in millimeters
- Select the appropriate grade or class
- Choose the lubrication state
- For custom fasteners, enter additional parameters as needed
- Click "Calculate Torque" to see the recommended values
Understanding the Results:
Recommended Torque: The ideal torque value for your fastener
Torque Range: The acceptable minimum and maximum values (typically ±5-10% of the recommended value)
Units: Results are provided in both Newton-meters (N·m) and foot-pounds (ft·lb) for convenience
Common Applications
Our Screw Torque Calculator is valuable for numerous applications including:
- Automotive Repair: Engine components, wheels, suspension parts
- Manufacturing: Assembly lines, product development
- Construction: Structural connections, equipment installation
- Woodworking: Furniture assembly, deck building
- Electronics: Assembly of electronic devices and enclosures
- Aerospace: Non-critical fastening applications
- DIY Projects: Home repairs, bicycle maintenance, appliance repair
Remember that while our calculator provides excellent guidance, always defer to manufacturer specifications for critical applications where safety is paramount.
Frequently Asked Questions
What's the difference between torque and tightening angle?
Torque measures the rotational force applied to a fastener, while tightening angle refers to the rotation of the fastener after initial seating. While our calculator focuses on torque values, some critical applications use a combined method called "torque-to-yield" or "torque-plus-angle" tightening. This involves applying a specific torque and then turning the fastener an additional specified angle to achieve precise clamping force. This method is commonly used for cylinder head bolts, connecting rod bolts, and other critical fasteners where precise preload is essential.
Why do lubricated fasteners require different torque than dry ones?
Lubrication significantly reduces friction between the threads and under the fastener head. With less friction, more of the applied torque translates into actual clamping force rather than being lost to friction. This is why lubricated fasteners typically require 20-40% less torque than dry ones to achieve the same clamping force. Using the torque value specified for dry fasteners on lubricated ones can result in excessive clamping force, potentially damaging the fastener or materials. Always consider the lubrication state when determining torque values.
How accurate are calculated torque values compared to manufacturer specifications?
While our calculator provides good estimates based on engineering principles, manufacturer specifications should always take precedence. Manufacturers perform extensive testing specific to their fasteners and applications. Calculated values typically have an accuracy of ±15-20% compared to tested values, which is adequate for many non-critical applications. However, for safety-critical applications—such as vehicle braking systems, structural components, or pressure vessels—always use the torque values specified by the manufacturer or relevant industry standards.