page_title: List of screw drives
section_title: Clutch
hierarchical_section_title: List of screw drives / Combination drives / Clutch
caption_attribution_description: English: Close-up of a clutch head screw used to fasten the fuel gauge sending unit to the fuel tank on a 1957 Chevrolet Bel Air sedan.
context_page_description: A screw drive is a system used to turn a screw. At a minimum, it is a set of shaped cavities and protrusions on the screw head that allows torque to be applied to it. Usually, it also involves a mating tool, such as a screwdriver, that is used to turn it. The following heads are categorized based on commonality, with some of the less-common drives being classified as "tamper-resistant".
  Most heads come in a range of sizes, typically distinguished by a number, such as "Phillips #00". These sizes do not necessarily describe a particular dimension of the drive shape, but rather are arbitrary designations.
context_section_description: There are two types of clutch screw drives: Type A and Type G. Type A, also known as a "standard clutch", resembles a bow tie, with a small circular "knot" at the center. These were common in GM automobiles, trucks and buses of the 1940s and 1950s. Type G resembles a butterfly, and lacks the center "knot". This type of screw head is commonly used in the manufacture of mobile homes and recreational vehicles. The clutch head was designed to be driven with a flat-blade screwdriver as well as a clutch driver.
caption: Type A clutch head screw
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