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The standard designation for a UTS thread is a number indicating the nominal (major) diameter of the thread, followed by the pitch measured in threads per inch.For diameters smaller than 1 / 4 inch, the diameter is indicated by an integer number defined in the standard; for all other diameters, the inch figure is given.
For example, “.750-10 UNC-2A” is male (A) with a nominal major diameter of 0.750 inches, 10 threads per inch, and a class-2 fit; “.500-20 UNF-1B” would be female (B) with a 0.500-inch nominal major diameter, 20 threads per inch, and a class-1 fit. An arrow points from this designation to the surface in question. [19]
Tables of BS Whitworth, BS Fine and BS Pipe Threads: V Thread Form (55°) 1 ⁄ 4 ″-20 BSW ISO 68-1:1998: ISO general purpose screw threads—Basic profile—Part 1: Metric screw threads: V Thread Form ISO 68-2:1998: ISO general-purpose screw threads—Basic profile—Part 2: Inch screw threads: V Thread Form ISO 261:1998
The design was first proposed by the British Association in 1884 [1] [2] with a thread angle and depth based on the Swiss Thury thread, [3] it was adopted by the Association in 1903. The Thury thread was different in that it went both positive and negative all the way up to a size of −20 which was 75.2 mm diameter by 8.23 mm pitch ( p ).
Many thread sizes have several possible tap drills, because they yield threads of varying thread depth between 50% and 100%. Usually thread depths of 60% to 75% are desired. People frequently use a chart such as this to determine the proper tap drill for a certain thread size or the proper tap for an existing hole.
Printable version; In other projects ... some US pipe thread sizes are widely used, as well as many British Standard Pipe threads and ISO 7–1, 7–2, 228–1, and ...
the thread size; Threads are normally right-hand. For left-hand threads, the letters, LH, are appended. Example: Pipe thread EN 10226 Rp 2 + 1 ⁄ 2. The terminology for the use of G and R originated from Germany (G for gas, as it was originally designed for use on gas pipes; R for rohr, meaning pipe.)
The screw itself should be drilled a minimum of 1" into the concrete to hold effectively and a maximum of 1-3/4" or the threads will wear and will lose holding power. Ideally 1-1/4" to 1-1/2" of screw thread in the concrete. [1] So for example, if a 1/2" board is being screwed onto the concrete, a 1-3/4" to 2" concrete screw should be used ...