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The trapezoidal metric thread form is similar to the Acme thread form, except the thread angle is 30°. [4] [5] [6] It is codified by DIN 103. [7] While metric screw threads are more prevalent worldwide than imperial threads for triangular thread forms, the imperially sized Acme threads predominate in the trapezoidal thread form.
A screw thread is an inclined plane wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. More screw threads are produced each year than any other machine element. [1] Threads are generally produced according to one of the many standards of thread systems.
The thread form is slightly modified to increase the minor diameter, and thus the strength of screws and taps. The major diameter still extends to within 1 / 8 H of the theoretical sharp V, but the total depth of the thread is reduced 4% from 5 / 8 H = 5 / 8 cos(30°) P ≈ 0.541P to 0.52P. [5]
Acme thread [6] 29° ASME/ANSI B1.5-1988 [7] Metric trapezoidal threads [1] Tr 30° DIN 103 Buttress threads [6] S 45° DIN 2781 German buttress threads [6] S 30° DIN 513 Square threads [1] Sq 0° (parallel) ? Panzergewinde, "steel conduit thread" Pg 80° DIN 40430 British Association (BA) thread: BA 47° 30' = 47.5° BS 93:2008 Löwenherz ...
where is the tap drill size, is the major diameter of the tap (e.g., 3 ⁄ 8 in for a 3 ⁄ 8-16 tap), and / is the thread pitch (1 ⁄ 16 inch in the case of a 3 ⁄ 8-16 tap). For a 3 ⁄ 8-16 tap, the above formula would produce 5 ⁄ 16, which is the correct tap drill diameter. The above formula ultimately results in an approximate 75% thread.
In oil field tubing, buttress thread is a pipe thread form designed to provide a tight hydraulic seal. The thread form is similar to that of Acme thread [10] but there are two distinct threaded portions of differing diameters and profiles, the larger having a wedging profile, with a tapered sealing portion in between the larger and smaller diameters.
Similarly, M10 (10 mm nominal outer diameter) as per ISO 261 has a coarse thread version at 1.5 mm pitch and a fine thread version at 1.25 mm pitch. The term coarse here does not mean lower quality, nor does the term fine imply higher quality. The terms when used in reference to screw thread pitch have nothing to do with the tolerances used ...
3 & 4: buttress thread 5: round thread 6: square thread DVD drive with leadscrew and stepper motor Floppy disc drive with leadscrew and stepper motor. A leadscrew (or lead screw), also known as a power screw [1] or translation screw, [2] is a screw used as a linkage in a machine, to translate turning motion into linear motion.