Shear Strength Testing of Fasteners – Complete Guide

Fasteners like bolts, screws, and studs are designed to hold components together under different types of loads. One of the most important mechanical properties of a fastener is its shear strength.

Shear strength testing determines how much force a fastener can withstand when the load is applied perpendicular (sideways) to its axis before failure.

In this guide, we explain shear strength testing of fasteners in simple language, including test methods, standards, calculations, and procedures.

What is Shear Strength of a Fastener?

Shear strength is the maximum load a fastener can handle before it breaks due to sideways force.

Unlike tensile strength (which pulls the bolt lengthwise), shear force tries to cut the bolt across its cross-section.

In simple words:

Tensile force = pulling force

Shear force = cutting force

Shear testing ensures the fastener can handle lateral loads safely.

Why Shear Strength Testing is Important?

Shear loads are common in:

• Structural steel connections

• Bridges and buildings

• Automotive assemblies

• Machinery joints

• Oil & gas structures

If shear strength is insufficient:

• Bolts may snap

• Joints may fail

• Equipment may collapse

• Safety hazards may occur

That’s why shear testing is critical in industrial fasteners.

Types of Shear Strength Tests

There are mainly two types of shear testing:

________________________________________

1. Single Shear Test

In a single shear test:

• One cutting plane is created

• Load is applied across one cross-section

• The fastener is cut into two pieces

This test is simpler but slightly less accurate compared to double shear.

________________________________________

2. Double Shear Test

In double shear test:

• Two shear planes are created

• The bolt is sheared at two points

• Load distribution is more balanced

Double shear testing gives more accurate and realistic results.

Shear Strength Testing Procedure (Step-by-Step Table)

Below is the standard procedure used in shear testing of fasteners

Shear Strength Testing Procedure of Fasteners

Step No.	Testing Step	Description
1	Sample Selection	Bolt or screw selected from production batch
2	Visual Inspection	Check for cracks, thread damage, surface defects
3	Mounting in Shear Fixture	Fastener placed in hardened steel shear jig
4	Alignment	Proper alignment ensured to avoid bending stress
5	Load Application	Load applied using Universal Testing Machine (UTM)
6	Controlled Loading Rate	Load increased at uniform speed
7	Failure Point Recording	Maximum load at failure recorded
8	Calculation	Shear strength calculated using formula
9	Reporting	Test report prepared with load & failure details

Shear Strength Calculation Formula

Shear Strength = Maximum Load at Failure ÷ Shear Area

Where: Shear Area = Cross-sectional area of bolt shank

For round bolts: Shear Area = p × d² ÷ 4 (d = bolt diameter)

Example: Bolt diameter = 10 mm

Failure load = 30,000 N

Shear strength = 30,000 ÷ Shear Area

Shear Strength vs Tensile Strength

Generally:

• Alloy steel shear strength ˜ 60% of tensile strength

• 300 series stainless steel ˜ 50–55% of tensile strength

Example:

If tensile strength = 800 MPa

Estimated shear strength ˜ 480 MPa

This is an approximation. Actual testing gives accurate values.

Standards for Shear Strength Testing

Shear testing is conducted as per international standards:

AISI S904-17

Standard for testing steel screws in cold-formed steel construction.

ISO Standards

Mechanical testing methods for fasteners.

ASTM Standards

Used for metals and composite material testing.

IS 5242 (1979)

Indian standard for shear strength testing of fasteners.

Following proper standards ensures reliable and accepted results worldwide.

________________________________________

Equipment Used in Shear Testing

Shear testing is performed using:

• Universal Testing Machine (UTM)

• Hardened steel shear fixtures

• Load measurement sensors

• Digital data recording system

Proper calibration of machine is mandatory for accurate results.

________________________________________

Factors Affecting Shear Strength

Several factors influence shear strength:

• Material composition

• Heat treatment

• Bolt diameter

• Threaded vs unthreaded section

• Surface finish

• Manufacturing quality

Higher grade fasteners generally provide higher shear strength.

________________________________________

Single vs Double Shear – Comparison Table

Feature Single Shear Double Shear

Shear Planes One Two

Accuracy Moderate High

Load Distribution Uneven Balanced

Common Usage Basic testing Structural testing

Result Reliability Good More accurate

________________________________________

Applications Where Shear Strength is Critical

Shear testing is important in:

• Structural steel joints

• Automotive chassis bolts

• Heavy equipment assembly

• Bridge construction

• Oil & gas structures

• Crane and lifting equipment

Proper shear strength ensures safe load-bearing performance.

________________________________________

Quality Testing at Pankaj International

At Pankaj International, we ensure:

Mechanical property testing

Shear and tensile testing

Proof load testing

Hardness testing

Dimensional inspection

Third-party inspection (if required)

Our fasteners are manufactured as per ASTM, ISO, DIN, and IS standards to ensure global quality compliance.

________________________________________

Conclusion

Shear strength testing of fasteners is a critical mechanical test that determines how much sideways force a bolt or screw can withstand before failure.

Single shear and double shear tests are performed using calibrated universal testing machines. Shear strength is calculated based on maximum load at failure divided by cross-sectional area.

For alloy steel fasteners, shear strength is typically around 60% of tensile strength, while stainless steel fasteners range between 50–55%.

If you are looking for high-quality industrial fasteners tested for shear strength and mechanical performance, Pankaj International is your trusted manufacturing partner.