Bahco 7455-300 Mechanical Torque Wrench User Manual

1. Introduction

This manual provides comprehensive instructions for the safe and effective operation, maintenance, and care of your Bahco 7455-300 Mechanical Torque Wrench. This precision tool is designed for applying specific torque values to fasteners, ensuring proper assembly and preventing damage from over or under-tightening. Please read this manual thoroughly before using the wrench.

2. Safety Information

Always observe the following safety precautions when using the torque wrench:

• Wear appropriate personal protective equipment, such as safety glasses.
• Ensure the workpiece is securely clamped before applying torque.
• Do not use the torque wrench as a breaker bar or for loosening fasteners. It is designed for tightening only.
• Avoid dropping the wrench, as this can affect its calibration and accuracy.
• Do not exceed the maximum torque capacity of the wrench (300 Nm).
• Keep the wrench clean and free from grease or oil to maintain a secure grip.
• Store the wrench in its protective case when not in use, and always set it to its lowest torque setting before storage to relieve spring tension.

3. Product Overview

The Bahco 7455-300 is a robust mechanical torque wrench featuring a 1/2-inch drive and a torque range of 60-300 Nm (Newton meters). It incorporates both metric and imperial scales for versatile application.

Figure 1: Bahco 7455-300 Mechanical Torque Wrench. This image displays the full length of the silver-colored torque wrench, showing the fixed square drive head on the left, the main body with visible metric and imperial scales, and the knurled adjustment handle on the right.

Key Features:

• Drive Size: 1/2-inch square drive.
• Head Type: Fixed head with 32 teeth, providing an 11.25° action angle for precise adjustments in confined spaces.
• Torque Range: 60-300 Nm (Newton meters) and equivalent imperial scale.
• Accuracy: ±4% for tightening operations, ±6% for reverse operations.
• Scales: Clearly marked metric (Nm) and imperial (ft-lb) scales.
• Construction: Durable silver finish, mechanical operation.

4. Setup

1. Unpacking: Carefully remove the torque wrench from its packaging. Inspect for any signs of damage.
2. Initial Setting: Before first use, ensure the wrench is set to its lowest torque value to relieve any tension from shipping.
3. Familiarization: Locate the main scale (Nm) and the micrometer scale (for fine adjustments). Identify the locking mechanism, typically at the base of the handle.

5. Operating Instructions

5.1 Setting the Torque Value

1. Unlock the Handle: Rotate the locking mechanism (usually a knurled ring at the base of the handle) counter-clockwise to unlock the adjustment handle.
2. Set Main Torque: Rotate the handle until the desired main torque value aligns with the center line on the main scale. For example, to set 100 Nm, rotate until the '100' mark on the main scale aligns with the edge of the micrometer scale.
3. Fine Adjustment: Continue rotating the handle until the desired fine adjustment value on the micrometer scale aligns with the center line. For example, if the main scale is at 100 Nm and you need 105 Nm, rotate the micrometer scale until '5' aligns with the center line. The total setting is 100 + 5 = 105 Nm.
4. Lock the Handle: Rotate the locking mechanism clockwise to securely lock the adjustment handle in place. Failure to lock the handle will result in inaccurate torque application.

5.2 Applying Torque

1. Attach Socket: Select the correct 1/2-inch drive socket for your fastener and attach it firmly to the wrench head.
2. Position Wrench: Place the socket onto the fastener. Ensure the wrench is positioned so that you can apply force smoothly and steadily.
3. Apply Force: Apply a slow, steady, and continuous pull or push to the handle. Do not use jerky movements.
4. Listen for Click: Continue applying force until you feel and hear a distinct "click" from the wrench. This indicates that the preset torque value has been reached.
5. Stop Immediately: Once the click is heard/felt, stop applying force immediately. Further tightening will result in over-torquing.
6. Reset for Next Use: After each use, it is recommended to reset the torque wrench to its lowest setting (60 Nm) to relieve tension on the internal spring, preserving its accuracy over time.

6. Maintenance

• Cleaning: Wipe the wrench clean with a soft, dry cloth after each use. Do not use solvents or harsh chemicals, as these can damage the finish or internal components.
• Storage: Store the torque wrench in its original protective case in a dry, clean environment. Always set the wrench to its lowest torque setting (60 Nm) before storage to prevent spring fatigue.
• Calibration: Torque wrenches are precision instruments and require periodic calibration to maintain accuracy. It is recommended to have your Bahco 7455-300 calibrated annually or after any significant impact or misuse by a qualified service center.
• Lubrication: The internal mechanism is factory-lubricated and generally does not require user lubrication. Unauthorized disassembly will void the warranty.

7. Troubleshooting

8. Specifications

9. Warranty and Support

For warranty information, technical support, or service inquiries regarding your Bahco 7455-300 Mechanical Torque Wrench, please refer to the warranty card included with your product or visit the official Bahco website. Do not attempt to repair the tool yourself, as this may void the warranty and compromise its accuracy and safety.

Bahco Official Website: www.bahco.com