Diameter of bolt given torque resisted by n bolts Calculator

Bolt Diameter Formula:

\[ d_{bolt} = \sqrt{\frac{8 \times T_{bolt}}{f_s \times \pi \times n \times d_{pitch}}} \]

Torque resisted by bolt (T_bolt):

N·m

Shear Stress in Bolt (f_s):

Number of Bolts (n):

Diameter of bolt pitch circle (d_pitch):

Tolerance:

Bolt Diameter (d_bolt):

1. What is a Bolt Diameter Calculator?

Definition: This calculator determines the required diameter of bolts needed to resist a given torque when multiple bolts are used in a circular pattern.

Purpose: It helps mechanical engineers and designers properly size bolts for applications involving rotational forces.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ d_{bolt} = \sqrt{\frac{8 \times T_{bolt}}{f_s \times \pi \times n \times d_{pitch}}} \]

Where:

\( d_{bolt} \) — Diameter of each bolt (meters)
\( T_{bolt} \) — Torque resisted by the bolts (Newton-meters)
\( f_s \) — Shear stress in the bolt material (Pascals)
\( n \) — Number of bolts in the pattern
\( d_{pitch} \) — Diameter of the bolt pitch circle (meters)

Explanation: The formula calculates the minimum bolt diameter needed to safely resist the applied torque without exceeding the material's shear stress limit.

3. Importance of Bolt Diameter Calculation

Details: Proper bolt sizing ensures structural integrity, prevents mechanical failure, and maintains safety factors in bolted connections under torque loads.

4. Using the Calculator

Tips: Enter the torque value, allowable shear stress, number of bolts, pitch circle diameter, and tolerance percentage (default ±5%). All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What is the bolt pitch circle diameter?
A: This is the diameter of the circle that passes through the center points of all the bolts in the pattern.

Q2: How do I determine the shear stress limit?
A: The shear stress limit is typically 60% of the bolt material's tensile yield strength for conservative designs.

Q3: Why include a tolerance percentage?
A: Tolerance accounts for manufacturing variations and safety factors. ±5% is common but may vary by application.

Q4: Can I use this for metric and imperial units?
A: Yes, but ensure all units are consistent (meters for lengths, N·m for torque, Pa for stress).

Q5: What if my calculated diameter isn't a standard size?
A: Always round up to the next available standard bolt size for safety.