At iFixit, Carsten Frauenheim writes:
It’s hard to keep track of all the different types of screws, fasteners, bolts, bits, and bobs that hold our lives together, from our fridges and phones to cars and planes. If you’ve ever poked around inside a gadget, you’ve probably come face-to-face with a 6-lobed, star-shaped screw.
That’s Torx. It and its new, high-tech cousin, Torx Plus, are the current kings of the screw hill. But what are they, and what makes them so special?
Although the original patents would dispute Frauenheim’s contention that one goal of the Phillips screw was to “cam out” (slip out when overtightened), that tendency remains problematic. Torx screws were introduced in the 1960s to prevent that behavior, utilizing six lobes with straight walls for a better grip. Torx Plus, developed in the 1990s, enhanced this design with elliptical lobes and perfectly vertical walls.
While this progression represents an engineering improvement, it creates a challenge for repair. Frauenheim says that standard Torx drivers will work (albeit not optimally) with Torx Plus screws, but Torx Plus drivers won’t fit in standard Torx screws at all. (Of course, Apple uses proprietary pentalobe screws and tamper-resistant tri-wing screws in addition to Torx and Torx Plus—I had no idea there were so many screw types.)
My main takeaway: it’s better to use a slightly smaller Torx driver than one that fits tightly, because the smaller one will reach the bottom of the screw socket and make more contact with the walls.
