The Fastener Torque Calculator is a precise engineering tool used to determine the correct torque needed to tighten a bolt or screw to achieve the desired clamping force. This calculation is crucial in mechanical and structural applications, as improper torque can lead to joint failure, component loosening, or even material damage.
By inputting values such as the bolt diameter, desired preload (clamping force), and a torque coefficient (which depends on lubrication and surface conditions), the calculator outputs the necessary tightening torque. This tool is highly applicable in automotive, aerospace, manufacturing, and construction industries where fastener integrity is vital.
This tool belongs to the Mechanical Engineering and Fastener Tools category.
formula of Fastener Torque Calculator
Torque (T) = K × D × F
Where:
T = torque applied to the fastener (in Newton-meters or inch-pounds)
K = torque coefficient or nut factor (dimensionless), usually ranges from 0.15 to 0.25
D = nominal diameter of the bolt (in meters or inches)
F = preload or axial clamping force (in newtons or pounds-force)
Supporting formula for calculating preload:
F = σ × A
Where:
σ = desired tensile stress (in pascals or psi)
A = tensile stress area (in square meters or square inches), often obtained from bolt specification charts
Metric Units:
T (Nm) = K × D (m) × F (N)
Imperial Units:
T (in-lbf) = K × D (in) × F (lbf)
This formula ensures that the joint achieves optimal clamping force without over-tightening or under-tightening.
Reference Table: Torque Estimates for Standard Bolts
| Bolt Size | K (Lubricated) | Preload (N) | Torque (Nm) |
|---|---|---|---|
| M6 | 0.18 | 7200 | 7.8 |
| M8 | 0.18 | 18000 | 25.9 |
| M10 | 0.20 | 28000 | 56.0 |
| M12 | 0.20 | 42000 | 100.8 |
| M16 | 0.22 | 80000 | 281.6 |
These are general estimates and should be verified with actual material and application conditions.
Example of Fastener Torque Calculator
Suppose you are tightening an M10 bolt with the following parameters:
K = 0.20 (standard lubricated condition)
D = 0.010 m (10 mm)
F = 28000 N (preload)
Torque = K × D × F = 0.20 × 0.010 × 28000 = 56 Nm
So, you would need to apply 56 Newton-meters of torque to achieve the required preload on the bolt.
Most Common FAQs
The torque coefficient depends on factors like thread condition, lubrication, and surface roughness. For dry bolts, it’s usually 0.2–0.3, while lubricated bolts are around 0.15–0.2. Manufacturer data or standards like ISO 16047 can provide exact values.
Yes, you can calculate in either metric or imperial units. Just make sure all your input values (bolt diameter, preload) use the same unit system.
Preload ensures that the bolt keeps the parts together under load and avoids loosening. It directly affects the strength and safety of the joint, especially in vibration-prone environments.