What the Impact Driver Does
An impact driver delivers short, powerful rotational blows when the tool meets resistance. This hammering action happens inside the tool, not on the fastener head. As you pull the trigger and the screw encounters harder material, the internal mechanism releases a burst of torque. This lets you drive long screws into dense wood without the tool twisting your wrist. The impact action is what makes the driver so effective, but it can also strip a screw head or snap the fastener if you do not adjust your technique.
Understanding that the impact only activates under load helps you anticipate when the tool will hammer. You can then control the trigger to avoid overdriving or camming out.
Start with Impact-Rated Hex-Shank Bits
Standard round-shank drill bits or hex bits meant for a chuck will not stay locked in an impact driver. The collet on an impact driver accepts only 1/4-inch hex-shank accessories. More importantly, the bits must be rated for impact use. Impact-rated bits are made from tougher materials, often with a torsion zone that flexes slightly to absorb the shock of the hammering blows. Non-rated bits can snap inside the driver or twist and break, leaving you with a stuck piece of steel in the collet.
Look for the words “impact rated” or “impact ready” on the bit packaging. These bits also tend to have a deeper, sharper cross-section in the tip, which grips the screw head more securely. That grip is essential for preventing cam-out, the slipping action that strips the recess.
Match Bit Size and Type to the Screw Head
A bit that is too small or too large for the screw recess will wobble and slip. Every time the bit slips, it rounds the edges of the screw head. Eventually, the driver cannot engage the fastener at all.
Phillips and Pozidriv are the two most common recess types in home improvement. A Phillips bit looks similar to a Pozidriv, but they are not interchangeable. Pozidriv has extra tick marks between the main cross slots. Using a Phillips bit in a Pozidriv screw head will cause slippage because the taper angles differ. Check the screw box or the fastener itself to confirm which recess you have. Square and star (six-lobe) recesses are more resistant to cam-out because the bit engages the full depth of the recess. For decking and other long screws, star or square drive screws are easier to drive without stripping.
Even within a type, bits come in numbered sizes. A #2 Phillips is the most common for general-use screws. A #1 or #3 will not fit correctly. Inspect the bit for wear. Dull or rounded bits should be replaced immediately because they are a primary cause of stripped screws.
Press Firmly in Line with the Screw
Apply firm, steady axial pressure straight down the axis of the screw. If you hold the driver at an angle, the bit will lever out of the recess as soon as the impact hammering starts. The force of each rotational blow pushes the bit sideways, and without enough downward pressure to keep it seated, the bit will skip across the head.
Keep your free hand away from the bit area entirely. If the bit slips, your hand could be struck by the tool or the spinning fastener. Brace the work with your free hand from the side or clamp the piece down instead.
Start Slowly with the Variable-Speed Trigger
An impact driver has a variable-speed trigger. Squeezing lightly gives you slow rotation. You should begin each screw at low speed, pressing the bit fully into the recess before the tool starts turning. Once the bit is seated and the screw begins to enter the material, you can increase speed gradually. This slow start prevents the bit from bouncing across the head before it finds purchase.
If your model has a speed selector switch or a dedicated mode selector (sometimes labeled “drill,” “screw,” or “impact”), set it to the lowest available speed or the screw-driving mode. Some impact drivers include a “precision drive” mode, which pauses the impact after the screw seats, then delivers a brief burst at low speed to finish. This helps avoid overtightening. Refer to the manufacturer instructions for your specific tool to understand what each mode does.
Stop When the Screw Is Seated
The most common cause of stripped heads and snapped screws is continuing to drive after the screw is tight. An impact driver has no adjustable clutch like a drill. It will keep hammering until you release the trigger. As soon as the screw head makes contact with the surface, ease off the trigger. If you need the screw slightly deeper, use a very short burst and check the depth visually. Overdriving not only strips the head but can also sink the screw so deep that it cracks the wood or breaks the fastener.
For outdoor projects or deck building, stop as soon as the screw head is flush. Driving deeper can compress the wood fibers and create a path for moisture.
Drill Pilot Holes in Hardwood and Near Board Ends
Hardwoods like oak, maple, or even dense plywood put up more resistance than soft pine. Without a pilot hole, the screw has to compress and cut its own path. The resistance builds quickly, causing the impact driver to hammer earlier and harder. That increases the chance of cam-out and stripping.
Drilling a pilot hole relieves that resistance. The general guidance is to choose a drill bit diameter equal to the screw’s minor diameter (the solid core of the screw, not the threads). For near the end of a board, a pilot hole also prevents the wood from splitting. Even in softwood, a pilot hole saves time and hardware when you are driving large screws or working close to an edge.
You can drill the pilot hole with a regular drill or a drill/driver before switching to the impact driver. Some impact drivers have a “drill” mode that disables the impact hammering, allowing you to drill a pilot hole with the same tool. Check your tool’s specs before using twist drill bits in an impact driver, because standard twist bits can be brittle under impact.
When a Drill with a Clutch Is the Better Choice
Not every fastening job calls for an impact driver. Small screws, furniture assembly, and work with delicate materials are better handled by a standard drill with an adjustable clutch. The clutch disengages the drive once a set torque level is reached. This prevents overtightening and stripping automatically. An impact driver lacks that feature. Its force is better suited for large deck screws, lag screws, and long fasteners into dense material.
If you are driving into thin sheet metal, particleboard, or soft plastics, the impact action can crack or split the material. Switch to a drill/driver and set the clutch to a low number. You can also use a drill clutch and speed settings guide to learn how to match the clutch setting to the screw size.
For furniture assembly with cam-lock fasteners or machine screws, an impact driver is too aggressive. Use a hand screwdriver or a drill with a light clutch setting.
Common Mistakes and Troubleshooting
Using a worn-out bit
If the bit looks shiny and rounded at the tip, replace it. A fresh bit grips the full depth of the recess and reduces slippage.
Skipping pilot holes
Driving a long screw into hardwood without a pilot hole builds resistance that triggers heavy impact hammering. That hammering can tear the screw head apart. Drill a pilot hole first.
Pulling the trigger too hard
Feathering the trigger gives you control. Pulling it wide open from the start makes the bit jump out of the recess. Practice squeezing slowly until the bit engages.
Using the wrong bit type for the screw head
Phillips vs. Pozidriv confusion is a common cause of stripped screws. Check the screw head carefully. Star or square drive bits are more forgiving for beginners.
Not seating the bit fully before starting
Insert the bit into the screw head before you pull the trigger. If you start the tool while the bit is hovering, you will likely damage the head before the bit seats.
Safety Reminders
Wear eye protection. Screws can snap and send fragments flying. Hearing protection is also wise because an impact driver under load produces a loud hammering noise that can damage hearing with extended use. Keep your free hand away from the bit area. If you hand-start a screw, hold the screw by its sides, not the top. Remove the battery before changing bits or clearing a jammed screw. Keep all guards and safety features in place. Read the tool manual for your specific model and follow all manufacturer instructions.
If you find yourself needing to reach into a tight space, a right-angle drill and attachment guide may help you access awkward fasteners while keeping your hands clear of the bit.
FAQ
Can I use regular drill bits in an impact driver?
Only if they have a 1/4-inch hex shank and are marked impact rated. Standard twist drill bits can shatter under the hammering action. Use impact-rated accessory bits for drilling in impact driver mode.
Why does my impact driver keep stripping Phillips screws?
You may be using a Phillips bit in a Pozidriv head, or the bit may be worn. Firm downward pressure and a slow trigger start also help. For heavy-duty driving, switch to star or square drive fasteners.
Should I use an impact driver for furniture assembly?
Usually not. The high torque and lack of a clutch make it easy to overtighten and strip small screws or damage particleboard. Use a drill with an adjustable clutch set low, or a hand screwdriver.
How do I remove a stripped screw?
Try a wide rubber band between the bit and the screw head for extra grip. If that fails, use a screw extractor kit or a left-hand drill bit. In some cases, you can cut a new slot in the head with a rotary tool and use a flathead screwdriver.
Using an impact driver skillfully means understanding how its impact force works, matching the bit to the fastener, controlling speed and pressure, and knowing when a different tool is the right choice. With practice, you can drive long screws into tough material quickly without ruining the fastener or the workpiece.
