1. Introduction
This manual provides essential information for the safe operation, maintenance, and troubleshooting of your DEWALT 20V MAX* 1/4 in. Brushless Cordless Impact Driver (DCF840B). Please read this manual thoroughly before using the tool to ensure proper function and to prevent injury.
The DEWALT DCF840B is a high-output 20V MAX* 1/4 inch Brushless Cordless Impact Driver designed for driving screws and other fasteners. Its brushless motor delivers up to 1,700 in-lb of torque and up to 3,200 rpm, making it suitable for various applications, including driving large-diameter screws. The compact and lightweight design enhances maneuverability, allowing access to confined areas. An integrated 3-LED work light improves visibility in dimly lit workspaces.
2. General Safety Instructions
Always follow basic safety precautions to reduce the risk of fire, electric shock, and personal injury when using power tools.
- Wear Eye Protection: Always wear appropriate eye protection, such as safety glasses or goggles, that comply with ANSI Z87.1.
- Hearing Protection: Use hearing protection during extended periods of operation.
- Respiratory Protection: Wear a dust mask or respirator when working in dusty environments.
- Maintain a Clean Work Area: Cluttered areas invite accidents. Keep your workspace well-lit and free from obstructions.
- Secure Workpiece: Always secure the workpiece with clamps or a vise. Holding the workpiece by hand is unstable and can lead to loss of control.
- Avoid Accidental Starting: Ensure the switch is in the OFF position before inserting the battery pack.
- Use the Right Tool: Do not force a small tool or attachment to do the job of a heavy-duty tool.
- Dress Properly: Do not wear loose clothing or jewelry. Contain long hair. Keep hair, clothing, and gloves away from moving parts.
- Stay Alert: Watch what you are doing, use common sense, and do not operate the tool when you are tired.
- Check for Damaged Parts: Before further use, carefully check the tool for proper operation and intended function.
- Do Not Operate in Explosive Atmospheres: Do not use power tools in the presence of flammable liquids, gases, or dust.
3. Product Overview
The DEWALT DCF840B Impact Driver is designed for efficiency and durability. Key components include the 1/4 inch hex chuck, variable speed trigger, forward/reverse button, LED work light, and belt hook.
Figure 1: Front angled view of the DEWALT DCF840B Impact Driver. This image shows the compact design, the 1/4 inch hex chuck, and the ergonomic grip.
Figure 2: Side view of the DEWALT DCF840B Impact Driver, highlighting the integrated belt hook for convenient carrying.
Key Features:
- High-Performance Brushless Motor: Delivers up to 1,700 in-lb of torque and 3,200 rpm for efficient fastening.
- Compact Design: Optimized for ergonomics and access to tight spaces.
- Variable Speed Trigger: Provides precise control over fastening applications.
- Integrated 3-LED Work Light: Illuminates dimly lit work areas for improved visibility.
- 1/4 inch Hex Chuck: Allows for quick and easy bit changes.
4. Setup and Assembly
4.1 Battery Installation and Removal (Battery Not Included)
The DEWALT DCF840B operates with a DEWALT 20V MAX* Lithium-Ion battery pack (sold separately).
- To install the battery pack, align the battery pack with the rails inside the tool's handle.
- Slide the battery pack firmly into the handle until it locks into place. Ensure it is fully seated and secure.
- To remove the battery pack, press the release button on the front of the battery pack and pull the battery pack out of the handle.
4.2 Installing and Removing Bits
The 1/4 inch hex chuck allows for quick and secure bit changes.
- To install a bit, pull the chuck collar forward and insert the hex shank of the bit fully into the chuck.
- Release the chuck collar. The bit should be securely locked in place. Pull on the bit to ensure it is properly seated.
- To remove a bit, pull the chuck collar forward and pull the bit out of the chuck.
5. Operating Instructions
5.1 Basic Operation
Before operating, ensure the battery is charged and properly installed, and the desired bit is securely in the chuck.
- Forward/Reverse Control: Push the forward/reverse button to the left for forward rotation (driving screws) and to the right for reverse rotation (removing screws). The center position locks the trigger.
- Starting the Tool: Squeeze the variable speed trigger to start the tool. The speed increases as you squeeze the trigger further.
- Stopping the Tool: Release the trigger to stop the tool.
Figure 3: Demonstrates the DEWALT Impact Driver in use, fastening a screw into a wooden deck board. Always ensure a firm grip and proper positioning.
5.2 Variable Speed Trigger
The variable speed trigger allows for precise control over the fastening speed. Apply light pressure for slower speeds and increased pressure for higher speeds. This feature is crucial for starting screws accurately and preventing overtightening or stripping.
5.3 LED Work Light
The integrated 3-LED work light activates when the trigger is pressed, illuminating the work surface. This feature is particularly useful in low-light conditions, enhancing visibility and accuracy.
6. Maintenance
Regular maintenance ensures the longevity and optimal performance of your impact driver.
- Cleaning: Use a clean, damp cloth to wipe down the tool. Do not use solvents or harsh chemicals. Keep the ventilation openings clear of dust and debris.
- Inspection: Periodically inspect the chuck for wear and ensure all screws are tight. Check the battery contacts for corrosion.
- Storage: Store the tool in a dry, secure location out of reach of children. Remove the battery pack when storing the tool for extended periods.
- Lubrication: This tool is factory lubricated and requires no additional lubrication.
7. Troubleshooting
Refer to the table below for common issues and their solutions.
| Problem | Possible Cause | Solution |
|---|---|---|
| Tool does not start. | Battery pack not installed correctly or discharged. Forward/reverse button in center (locked) position. | Ensure battery pack is fully inserted and charged. Move forward/reverse button to desired operating position. |
| Reduced power or speed. | Low battery charge. Overload condition. | Recharge battery pack. Reduce pressure on the tool or use a larger bit if necessary. |
| Bit not holding securely. | Chuck collar not fully released after bit insertion. Worn bit shank. | Ensure chuck collar snaps back into place. Replace worn bits. |
| Tool overheating. | Continuous heavy use. Blocked ventilation slots. | Allow tool to cool down. Clear any obstructions from ventilation slots. |
8. Specifications
Detailed technical specifications for the DEWALT DCF840B Impact Driver.
Figure 4: Back view of the impact driver, displaying the product label with model number and basic specifications.
| Feature | Detail |
|---|---|
| Brand | DEWALT |
| Model Number | DCF840B |
| Power Source | Battery Powered (20V MAX* Lithium Ion) |
| Maximum Rotational Speed | 3200 RPM |
| Voltage | 20V |
| Maximum Chuck Size | 0.25 Inches (1/4 inch Hex) |
| Color | Yellow |
| Included Components | Tool, Belt Hook (Battery and Charger Sold Separately) |
| Special Feature | Variable Speed, 3-LED Work Light |
| Product Dimensions | 4.8"L x 4"W x 9"H |
| Material | Blend, Metal |
| Maximum Torque | 1700 Inch Pounds |
| Item Weight | 0.01 Ounces (Tool Only) |
| Maximum Power | 300 Watts |
| Drill Type | Impact Driver |
| UPC | 885911725927 |
| Batteries Required? | Yes |
| Battery Cell Type | Lithium Ion |
9. Warranty and Support
This DEWALT tool is covered by a Manufacturer Warranty. For specific details regarding warranty coverage, limitations, and how to make a claim, please refer to the warranty card included with your product or visit the official DEWALT website.
For technical assistance, service, or to locate an authorized service center, please contact DEWALT Customer Service or visit their official website:
- DEWALT Official Website: www.dewalt.com
- Customer Support: Refer to the contact information provided on the DEWALT website or your product packaging.
Please retain your proof of purchase for warranty purposes.
