Cam out happens when your screwdriver bit slips out of the screw head while turning it. It’s annoying, damages the fastener head or bit, and causes more cursing than most of us would like to admit.
What is Cam Out?
- Cam out happens when the bit tip slips out of the fastener head
- The spinning in and out of the fastener recess damages either the head or the bit
- Use the correct size bit for the fastener
- Be sure you’re setting the bit straight into the fastener
- Square head, Torx head, and star head fasteners reduce cam out
- Using a socket or nut driver with hex head fasteners will also reduce cam out
What Causes Cam Out?
Camming out a screw, unfortunately, is not particularly uncommon, especially when working with Phillips head screws. These taper in toward the center just like the driver bit tip.
When you pull the trigger on your driver, the spin pushes the insides of the screw, turning it. When you don’t put enough downforce to engage the fastener or you’re working at an angle into it, the torque from your driver can push the bit up and out.
Since drill and impact drivers spin at such high speeds, the bit pushes in and out of the fastener head hundreds of times before you let go of the trigger.
Cheap, soft screws will cam out their heads and make it very difficult to finish the drive or back them out. Sometimes the bit is the softer metal and it starts to round off. Another possibility is that both materials are hard and the bit tip breaks off.
How To Avoid Cam Out
Check Your Tool
One way to avoid cam out is to make sure that you’re using the right size bit for the screw you’re trying to turn. When you’re checking, set the bit in and give a wiggle. There shouldn’t be much play. If there is, go to the next size up.
For instance, before you install any screws, check the sizing on the side of the box. If you’re using a #2 Phillips head, you’ll want a #2 Phillips driver. These will fit pretty snug and a quality bit and fastener pair will barely move at all.
You’ll also want to check the bit itself. Even with proper use, they wear down and round out over time. A worn bit will cam out easier than a new one.
Keep your bit straight up and down while you’re driving. Any tilting will transfer force to the screw unevenly, ultimately causing the bit to disengage and cam out.
When it comes to using a handheld screwdriver, there’s a balance between pushing and turning force. Basically, you can push the bit or driver into the screw with some force, but be more careful with the turning. The folks at NBK recommend applying a 70%/30% pushing to turning force ratio.
Switch To A New Screw
There are quite a few bit and fastener styles available that can help avoid cam out. With more surface area and grip, square, star, and Torx bits and screws avoid stripping out and transfer more torque more easily.
Rather than having a tapered recess and four points of surface area to turn with, the Torx design provides more contact area to grip while maintaining a consistent depth in the head. Cam out with these hexalobular bits is almost impossible as long as you keep the bit heading straight in.
You can also go with a hex head fastener and use a nut driver or socket for many applications. By surrounding the head instead of sliding into it, it’s much easier to keep the pair engaged.
Like the impact driver from the photo? It’s the Makita XDT12 – check out the review here!