Types of Screw Head Bits

Written by shane grey
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Types of Screw Head Bits
The Phillips bit is a common type of screw head bit (kreuzschrauben und bit image by Wolfgang Dietz from Fotolia.com)

Screw head bits, also called screwdriver bits, appear across the breadth of the building, maintenance and repair industries. Auto mechanics require screw bits for engine, body and interior work, carpenters and roofers for driving fasteners, electricians for wiring terminals and plumbers for installing fixtures. Additionally, manufacturers produce specialised screw bits and screws to increase driving power and security.


The Phillips-head screw bit employs a simple, crossed design. Viewed from above, Phillips-head screws feature two, perpendicularly placed slots that resemble a cross of four equal bars. The screw bit itself tapers to a point. Fine-tipped Phillips bits fit into small-headed screws and blunt-tipped Phillips bits fit into large-diameter screws.


The slotted screw head bit, also referred to as the "flat-head" screwdriver bit, features a single, straight-edged tip. The screws that correspond to this simply designed bit appear as a single slot across the fastener's head.


Star screw head bits typically appear as a star of either 6 or 8 points. The multiple points of the star head bit tightly fit into their corresponding slot, allowing workers to apply extra torque and reduce the occurrence of stripping and slipping during the fastening process.


In colloquial U.S. English, the term "spanner" bit refers to a dual-pronged screw bit. Two thin rods protrude from the end of the bit and snugly fit into corresponding holes atop the head of a screw. The primary advantage of a spanner bit is its relative rarity; it is used frequently as a type of security screw.


The square screw head bit, sometimes called a "square drive" bit, forms a precise, four-sided square at its tip. This bits hole extends deep into the head of its screw, providing the bit's user with increased gripping strength and reduced slipping.


The one-way screw head bit tightens a classic, one-way "security screw." The term security screw refers to a screw that discourages removal. The one-way screw features a straight slot surrounded by roughly wedge-shaped channels. This unique design allows it to be tightened by the average slotted screwdriver, but removed only with a specially designed screw head bit. The only tool capable of removing the one-way screw, the one-way screw head bit, engulfs the screw's head like a socket wrench's socket. Inside the bit's socket, a moulded piece of metal fits precisely into the screw's unusual head slots, allowing for both removal and tightening.

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