# Bolt Torque Clamp Force Calculator

Convert between bolt tightening torque and axial clamp force. T = K·F·d, where K is the nut factor (~0.20 for dry steel). Solve torque from force, or force from torque.

> Canonical page: https://elysiatools.com/en/tools/bolt-torque-clamp-force

- **Category:** Math & Numbers

- **Keywords:** bolt torque, clamp force, preload, nut factor, tightening torque, fastener, mechanical engineering

## Overview

The Bolt Torque Clamp Force Calculator allows mechanical engineers and technicians to easily convert between bolt tightening torque and axial clamp force using the standard formula T = K·F·d. By inputting the nut factor, bolt diameter, and either the target clamp force or applied wrench torque, you can quickly determine the corresponding mechanical values required for secure fastener assembly.

## Inputs

- **Calculation Mode** (select)
- **Nut Factor K** (number): Dimensionless nut factor. Typical: 0.20 dry steel, 0.15 lubricated, 0.13 with moly.
- **Clamp Force F (kN)** (number): Axial clamp force in kN. Required in Torque mode.
- **Bolt Diameter d (mm)** (number): e.g. 10
- **Wrench Torque T (N·m)** (number): Applied wrench torque in N·m. Required in Force mode.
- **Decimal Places** (number)

## When to use

- When designing bolted joints and needing to determine the required tightening torque to achieve a target axial clamp force.
- When verifying if an applied wrench torque will exceed the yield strength or safety limits of a specific bolt diameter.
- When adjusting assembly specifications for different lubrication states by changing the dimensionless nut factor (K).

## How it works

- Select the calculation mode: either 'Torque from force' to find the required torque, or 'Force from torque' to find the resulting clamp force.
- Enter the dimensionless nut factor (K), which represents friction conditions (e.g., 0.20 for dry steel, 0.15 for lubricated threads).
- Input the bolt diameter in millimeters and provide either the clamp force in kilonewtons (kN) or the wrench torque in Newton-meters (N·m) depending on the selected mode.
- Click calculate to solve the equation T = K·F·d and view the computed value rounded to your preferred decimal places.

## Use cases

- Calculating assembly torque specifications for structural steel bolts during construction.
- Estimating clamping force generated by pneumatic torque wrenches on automotive cylinder head bolts.
- Adjusting torque values for maintenance procedures when switching from dry to lubricated fasteners.

## Frequently asked questions

### What is the nut factor (K)?

The nut factor is a dimensionless value representing the friction in the bolt threads and bearing face, typically ranging from 0.10 to 0.30.

### What units are used for the inputs?

The calculator uses millimeters (mm) for bolt diameter, kilonewtons (kN) for clamp force, and Newton-meters (N·m) for wrench torque.

### How does lubrication affect the torque calculation?

Lubrication lowers the nut factor (K), meaning less torque is required to achieve the same axial clamp force compared to dry steel.

### Can I calculate the clamp force if I only know the torque?

Yes, select the 'Force from torque' mode, enter your applied torque, bolt diameter, and nut factor to find the resulting clamp force.

### Is thread pitch accounted for in this formula?

No, this calculator uses the simplified T = K·F·d formula, which aggregates thread geometry and friction into the single nut factor (K).

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