Screwdrivers with anti-cam-out tips or ribs (ACR) offer an improved tool-fastener grip that reduces cam-out and potential fastener damage. Less slippage also translates to greater power transmission, and more efficient screwdriving.
What Makes Them Resist Camming-Out?
Anti-cam-out screwdrivers or screwdriver bits have tips that have either raised ribs or recessed grooves. The edges of these ACO/ACR features dig into the inner walls of fasteners, creating additional friction that helps the driver resist camming-out of the fastener.
Are Anti-Cam-Out Screwdrivers Better than Ordinary Drivers?
Not necessarily, but they absolutely do come in handy when you need an extra bit of grip on a fastener. These days I tend to use ACO/ACR drivers more on slotted screws than Phillips. That’s mostly because I try to use Robertson/square drive screws for most woodworking projects, and hex for most of my other projects.
Phillips screwdrivers are actually designed to cam out from a fastener to avoid applying excessive torque. While I’ve never sheared the head off a screw using a handheld screwdriver, I have damaged plenty of [cheaper/lower quality] fasteners, making their future removal difficult.
ACR drivers are also handy when dealing with partially stripped screwdriver heads. The extra grab they provide can be just enough to loosen a screw before a screw extractor is needed as a last resort.
I use two brands of ACR drivers on a regular basis – 3K ACO drivers from Wiha, and Kraftform Plus drivers from Wera. These days most quality screwdrivers have decent tip coatings that also improve fastener grip, but they’re no substitute for true ACO/ACR grooves.
Product Info via Wera