You keep stripping screws because your driver bit is slipping inside the screw head instead of turning it. This is called cam-out, and it happens when the force you’re applying gets redirected upward along the shaft of your screwdriver instead of rotating the screw. The good news: it’s almost always caused by a handful of fixable mistakes in technique, tool choice, or preparation.
How Cam-Out Destroys Screw Heads
The Phillips screw head, by far the most common type in household projects, has a conical shape that tapers toward the bottom of the cross-shaped recess. When you apply torque, some of that energy doesn’t rotate the screw. Instead, it creates an axial force that pushes the driver bit upward and out of the head. Each time the bit slips, it shaves away a tiny amount of metal from the recess walls. Do that enough times and the recess becomes a smooth, rounded bowl that no bit can grip.
This effect gets dramatically worse with power tools. A drill spinning at high speed can strip a screw head in a fraction of a second because the bit is moving too fast for you to react when it starts to slip. The higher the torque, the stronger that upward ejection force becomes.
The Most Common Causes
Wrong Size or Worn-Out Bit
This is the number one reason people strip screws repeatedly. Phillips bits come in sizes #0 through #4, and using a #2 bit on a #1 screw (or vice versa) leaves gaps between the bit and the recess walls. Those gaps mean less contact surface, which means the bit slips under much less torque than it should. The fit should feel snug when you press the bit into the screw head before you start driving.
Worn bits cause the same problem. After dozens or hundreds of screws, the sharp edges of a driver bit round off. The deformation is subtle enough that you might not notice by looking, but the bit no longer seats fully into the recess. If you’ve been using the same bit for a while and screws are suddenly stripping more often, swap in a fresh one before blaming anything else.
Not Enough Downward Pressure
Because of that conical Phillips shape, you need to actively push the bit into the screw while turning. If you ease up on pressure, the cam-out force wins and the bit rides up out of the head. This is especially common when driving screws overhead or at awkward angles where it’s hard to lean into the work. A good rule: press harder than you think you need to, particularly for the first few turns and the last few turns when resistance is highest.
No Pilot Hole
Driving a screw directly into wood without a pilot hole forces the screw to displace all that material on its own. The resistance can be enormous, especially in hardwoods like oak or maple. All that extra resistance means more torque on the screw head, which means more cam-out force. Drilling a pilot hole first reduces driving torque dramatically because the screw threads only need to bite into surrounding wood rather than bore through solid material.
Pilot hole sizing matters. For a common #8 screw in hardwood, you want roughly a 1/8-inch straight bit. In softwood like pine, drop down to 7/64 inch. Go too large and the screw won’t hold; go too small and you’re back to excessive resistance. For larger #10 screws, use 9/64 inch in hardwood and 1/8 inch in softwood. When in doubt, the pilot hole should be slightly smaller than the screw’s inner shaft (the solid core, not the outer thread diameter).
Too Much Speed on the Drill
Running your drill at full speed while driving screws is a recipe for stripped heads. High RPMs give you almost no time to feel when the bit starts to slip. Slow the drill down, especially as the screw head approaches the wood surface. That final quarter-inch is where resistance spikes and most stripping happens. Many drills have a low-speed setting or a clutch with numbered torque settings. Use the clutch: set it low enough that the drill disengages before the bit can strip the head.
Why Phillips Screws Strip So Easily
Phillips screws were actually designed to cam out. When they were introduced in the 1930s, the self-centering cross shape was meant to prevent overtightening on assembly lines. The bit would pop out of the head once torque got too high. That was a feature for factory automation. It’s a frustrating flaw for everyone else.
Pozidriv screws, which look similar but have four extra notches between the cross arms, improved on Phillips by offering better grip. They still use the same basic conical geometry, though, so they can still slip and strip under high torque.
Torx (star-shaped) screws take a fundamentally different approach. Their six-lobed design distributes force radially, meaning outward across six contact points, rather than creating that upward axial force. This eliminates cam-out entirely. You can apply significantly more torque to a Torx screw without the bit slipping, which is why they’ve become standard in construction, automotive, and deck-building applications. If you’re buying screws for a project and have the choice, Torx-drive screws will save you a lot of frustration.
Impact Drivers vs. Drills
If you strip screws regularly with a standard drill, switching to an impact driver can make a noticeable difference. Impact drivers deliver torque in rapid rotational bursts rather than continuous spinning. Each burst drives the bit deeper into the screw head, maintaining contact and reducing cam-out. They also give you better contact with the screw head overall, resulting in fewer stripped heads.
The tradeoff is control. A drill lets you feather the trigger for precise, slow rotation. An impact driver is more of an all-or-nothing tool. For delicate work like brass screws or thin materials, a drill with a properly set clutch is still the better choice. For driving dozens of screws into framing lumber or decking, an impact driver is the clear winner.
How to Remove a Screw That’s Already Stripped
Once a screw head is rounded out, a standard bit won’t grip it. Here are the approaches that actually work, roughly in order of how stripped the head is.
- Wide rubber band method. Place a wide rubber band flat over the stripped head, then press your driver bit through the rubber band into the recess. The rubber fills the gaps and adds friction. This works well for screws that are only partially stripped.
- Valve grinding compound. This abrasive paste, available at any auto parts store, dramatically increases friction between the bit and screw head. Dab some into the stripped recess, seat your bit, and try again. Mechanics have used this trick for decades on stubborn fasteners.
- Manual impact driver. This is a handheld tool you strike with a hammer. The impact converts downward force into rotational force, seating the bit firmly while turning the screw. Extremely effective for screws that are both stuck and stripped.
- Screw extractor bit. These reverse-threaded bits are designed to bite into damaged screw heads. You drill a small hole into the center of the stripped screw, then the extractor grips the inside of that hole and backs the screw out. This is the nuclear option for badly damaged screws.
- Cut a new slot. If the screw head is accessible and above the surface, use a rotary tool or small hacksaw to cut a straight slot across it. Then use a flathead screwdriver to back it out.
Habits That Prevent Stripping
Most screw stripping comes down to preparation and patience. Drill pilot holes, especially in hardwood. Use the correct size bit and replace bits that show any rounding. Set your drill’s clutch to a moderate level rather than driving at full torque. Slow down as the screw head nears the surface. Push firmly into the screw while turning.
If you’re starting a new project, consider buying Torx-drive screws instead of Phillips. The price difference is negligible, and you’ll spend far less time fighting stripped heads. Keep a few sizes of fresh driver bits on hand, since a sharp bit with clean edges is the single most effective prevention against cam-out. A $3 replacement bit is cheaper than the time and frustration of extracting a stripped screw from a finished piece of work.