Fastener Design Data, Calculations and Thread Standards
This page provides engineering data and design guidance for threaded fasteners, including screws, bolts and threaded systems. It covers thread dimensions, preload, torque, stress areas and bolted joint performance.
Studs – used in high strength or repeated assembly applications
Washers – used to distribute load and prevent loosening
Threaded rods – used in structural and anchoring applications
Fastener Design Considerations
When designing bolted joints, engineers must consider preload, shear loads, tensile stress, thread engagement and fatigue. Proper tightening torque and thread selection are critical to ensure joint reliability and prevent failure.
For tapped holes, the thread engagement (based on nominal diameter D) and tapping drill size must be carefully selected to ensure adequate thread engagement. Typical guidance suggests:
Typical Thread Engagement and Tapping Drill Sizes
The following table provides typical guidance for thread engagement and tapping drill sizes for common metric fasteners. Values are indicative and should be verified for specific materials and applications.
Thread Size
Pitch (mm)
Tapping Drill (mm)
Recommended Engagement
Approx. Engagement Length
M3
0.5
2.5
0.25 × D
0.75 mm
M4
0.7
3.3
0.25 × D
1.0 mm
M5
0.8
4.2
0.20 × D
1.0 mm
M6
1.0
5.0
0.20 × D
1.2 mm
M8
1.25
6.8
0.20 × D
1.6 mm
M10
1.5
8.5
0.20 × D
2.0 mm
M12
1.75
10.2
0.20 × D
2.4 mm
M16
2.0
14.0
0.15 × D
2.4 mm
Note: Softer materials such as aluminium typically require greater thread engagement (up to 1.0 × diameter), while high-strength steel joints may require less.
Applications of Fasteners
Mechanical assemblies and machine construction
Structural steel and construction joints
Automotive and aerospace components
Pressure vessels and piping systems
Maintenance and repair operations
Advantages of Threaded Fasteners
Allow easy assembly and disassembly
Wide range of standard sizes and types
Reliable load transfer in tension and shear
Suitable for many materials and applications
Cost-effective and widely available
Limitations of Fasteners
Can loosen under vibration if not secured
Stress concentrations at threads
Requires correct preload for performance
Potential for corrosion and fatigue failure
Installation errors can lead to joint failure
Frequently Asked Questions
What are fastener engineering tables used for?
They provide standard data for bolt strength, torque, thread dimensions and joint design calculations.
Why is preload important in bolted joints?
Preload ensures the joint remains secure and prevents loosening under load or vibration.
What is a stress area in a screw?
The stress area is the effective cross-sectional area used to calculate tensile strength.
How is tightening torque determined?
Torque is calculated based on bolt size, friction conditions and required preload.
What is thread engagement?
Thread engagement is the length of thread contact needed to safely transmit loads.
Suppliers sites with Screw sizes/Specs
Fuller metric.. Extensive range on DIN/ISO standard screws with dimensions
