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The rods are bent to 90º, forming two arms of unequal length resembling an "L". The tool is usually held and twisted by its long arm, creating a relatively large torque at the tip of the short arm; it can also be held by its short arm to access screws in difficult-to-reach locations and to turn screws faster at the expense of torque. [1]
Torque charts are available to specify the required torque for a given fastener based on its property class (fineness of manufacture and fit) and grade (tensile strength). Spring Analogy for a Bolted Joint. When a fastener is tightened, a tension preload is develops in the bolt, while an equal compressive preload forms in the clamped parts.
Robertson screwdrivers are easy to use one-handed, because the tapered socket tends to retain the screw, even if it is shaken. [3]: 85–86 They also allow the use of angled screwdrivers and trim-head screws. The socket-headed Robertson screws are self-centering and reduce cam out. They also stop a power tool when set, and can be more easily ...
The screw thread concept seems to have occurred first to Archimedes, who briefly wrote on spirals as well as designed several simple devices applying the screw principle. Leonardo da Vinci understood the screw principle, and left drawings showing how threads could be cut by machine. In the 1500s, screws appeared in German watches, and were used ...
The number series of machine screws has been extended downward to include #00-90 (0.047 in = 0.060 in − 0.013 in) and #000-120 (0.034 in = 0.060 in − 2 × 0.013 in) screws; [3] however, the main standard for screws smaller than #0 is ANSI/ASME standard B1.10 Unified Miniature Screw Threads. This defines a series of metric screws named after ...
The torque applied to the fastener must be determined such that it does not contribute to a service condition where the fastener enters a low-cycle fatigue regime. In general, the use of torque-to-yield fasteners is deprecated except in cases where the materials and structures comprising the entire assembly are certified to be within tolerances ...
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The term fine adjustment screw typically refers to screws with threads from 40–100 TPI (Threads Per Inch) (0.5 mm to 0.2 mm pitch) and ultra fine adjustment screw has been used to refer to 100–254 TPI (0.2 mm to 0.1 mm pitch). These screws are most frequently used in applications where the screw is used to control fine motion of an object.