Description:

Key Features

High Fastening Power The brushless motor delivers up to 1,700 in-lbs of torque with up to 3,200 RPM, giving this impact driver the muscle for large fasteners and tougher driving work without stepping up to a bulkier tool. Compact Reach At just 5.625 inches long, the DEWALT DCF840B 20V MAX 1/4 in. Brushless Cordless Impact Driver is built to get into framing bays, cabinetry, and other tight spots where full-size tools get awkward fast. Control in Low Light A variable speed trigger helps you ease into the fastener instead of stripping it, and the integrated 3-LED work light keeps the bit and screw visible when you are working in dim corners or under framing.

Overview

The DEWALT DCF840B 20V MAX 1/4 in. Brushless Cordless Impact Driver is a compact cordless fastening tool built for driving screws, lag screws, and other common jobsite fasteners with more control than a drill and more access than a larger impact. This is a cordless impact driver designed for fastening in framing, cabinetry, remodeling, and general construction work. Model Number: DCF840B. If you already run on the DEWALT 20V MAX platform and want a bare tool that stays light in the hand without giving up real driving power, this is the kind of impact driver that makes sense.

What matters here is the balance between output and size. The brushless motor delivers up to 1,700 in-lbs of torque, up to 3,200 RPM, and up to 4,200 impacts per minute. In plain terms, that means it has enough power for large-diameter screws and tougher fastening while still giving you the speed to keep moving through repetitive work. The variable speed trigger is not just a spec-sheet item either. It gives you a better start on delicate hardware and a cleaner approach when you need to seat a fastener without overdriving it.

DEWALT kept this tool compact at 5.625 inches long, and that makes a real difference on the job. When you are working between studs, inside cabinets, under decks, or in mechanical spaces, short length matters more than most people think. It lets you keep the bit square to the fastener without twisting your wrist into a bad angle. That shorter nose also helps when you need one-handed control while reaching into a tight spot.

Weight is another reason this tool will appeal to a lot of users. At about 2.2 lbs, it is light enough for overhead fastening, punch-list work, and all-day carry on a belt hook without feeling like dead weight by lunch. The compact and ergonomic layout is there for a reason: less bulk means less fatigue, especially for trades that spend the whole day driving fasteners instead of just grabbing an impact driver once in a while.

For real-world jobsite use, the built-in 3-LED work light is a practical feature, not fluff. If you have ever driven screws in a dim utility room, inside a cabinet box, or late in the day under framing, you know how much easier it is when the bit, fastener head, and work surface are all visible. That added visibility also helps reduce cam-out and stripped heads because you can actually see your bit engagement before you pull the trigger.

The DCF840B uses a 1/4 inch hex drive, which is the standard setup most impact driver users want because bit changes are quick and accessory selection is easy. It is part of the DEWALT 20V MAX battery system, so this bare tool is a good buy for anyone who already owns compatible DEWALT lithium-ion batteries and chargers. Batteries and charger are not included, which is worth knowing up front, but that is exactly what many existing DEWALT users want when they are adding another fastening tool to the trailer or replacing an older body.

This model is a strong fit for carpenters, remodelers, deck builders, installers, general contractors, and serious DIY users who want a compact impact driver with enough output for more than light assembly work. It is especially well suited to anyone who values reach, light weight, and daily-use comfort but still needs real fastening performance for framing screws, cabinet installation, ledger hardware, and general construction fastening.

Built for Tight-Space Fastening

Compact size is the whole story with this tool. When you are fastening between framing members or reaching into deck and cabinet work, a shorter impact driver gives you a straighter shot and better wrist position.

• Tool length of 5.625 in. helps it fit where bulkier impact drivers fight for space
• Lightweight body at 2.2 lbs reduces fatigue during repetitive fastening
• Belt hook keeps the tool close when you are moving up ladders or around a jobsite

Power for Larger Fasteners

This is not just a light-duty installer tool. The DCF840B has the output for tougher fastening jobs where smaller impacts start to stall or make you wait on every screw.

• Brushless motor delivers up to 1,700 in-lbs of torque
• Up to 3,200 RPM keeps driving speed up on repetitive work
• Up to 4,200 impacts per minute helps maintain momentum under load

What's in the Box

• (1) DEWALT DCF840B impact driver
• (1) Belt hook

Battery and charger are sold separately.

Key Specifications

Compatibility

Battery Platform Compatible with the DEWALT 20V MAX lithium-ion battery system. Charger Fit Uses DEWALT 20V MAX chargers. This bare tool does not include a charger. Bit Interface 1/4 in. hex drive accepts standard impact driver bits and bit holders built for hex-shank fastening accessories.

Built For

Carpentry Construction General Contracting Remodeling Cabinet Installation Framing Deck Building DIY / Hobbyist

Pro Tip

When you are driving larger screws or starting a spade bit, feather the variable speed trigger for the first second to keep the bit seated and the fastener straight. That matters even more with a compact impact driver because you can stay square in tight spaces and avoid chewed-up heads.

Warranty & Support

3-year limited warranty, 1-year free service, and 90-day money-back guarantee.

Tool Nut's Take

Tool Nut's Take

DEWALT DCF840B 20V MAX 1/4 in. Brushless Cordless Impact Driver Hits the Sweet Spot

This is the kind of impact driver a lot of pros actually end up reaching for most because it stays compact, light, and fast while still bringing enough torque for real jobsite fastening.

• Who it's for: DEWALT 20V MAX users who want a daily-driver impact for framing, cabinet installs, deck work, punch-list jobs, and general screw fastening.
• Why it stands out: You get 1,700 in-lbs of torque, 3,200 RPM, a brushless motor, and a very compact 5.625 in. length in one bare tool package.
• Worth knowing: This is tool-only, so it is a better value if you already own DEWALT batteries and a charger. If you do, it is an easy add to the kit.

Common Questions

• Is this a brushless impact driver? Yes. The DCF840B uses a brushless motor.
• What battery platform does it use? It is part of the DEWALT 20V MAX system and uses compatible DEWALT 20V MAX lithium-ion batteries.
• What type of bits does it accept? It uses a 1/4 in. hex drive for standard impact driver bits and hex-shank accessories.
• Does it have a work light? Yes. It has an integrated 3-LED work light for dim work areas.