Chapter 1 Measurement of the length of the world today, there are two major units of measurement, a for the metric system, units of measurement for the meter (m), centimeters (cm), millimeters (mm) and so on, in Europe, China and Japan, Southeast Asia, the use of more more than another for the British, the main unit of measurement for the inch (inch), equivalent to China's old system of city-inch, in the United States, Britain and other European and American countries use more. 1, Metric Measurement: (10 M) 1m = 100 cm = 1000 mm 1 cm 0 1 2 3 4 5 6 7 8 9 10 mm 2, imperial measures: (8 M) 1 inch = 8-British sub-1 inch = 25.4 mm 3 / 8 ¢ ¢ × 25.4 = 9.52 1 / 16 3 / 16 5 / 16 7 / 16 9 / 16 11/16 13/16 15/16 0 1 / 8 1 / 4 3 / 8 1 / 2 5 / 8 3 / 4 7 / 8 1 inch 3,1 / 4 ¢ ¢ product with the following code to indicate its title track, such as: 4 #, 5 #, 6 #, 7 #, 8 #, 10 #, 12 #
Chapter II Thread
A thread is a solid or the inner surface of the outer surface of the cross-section, a uniform shape protruding helix. According to their structural characteristics and uses can be divided into three categories:
(A), the general thread: for the triangular-shaped teeth for connecting or fastening parts. Common thread is divided into coarse teeth by the pitch and fine threads of two teeth, small teeth of the connecting thread a higher intensity.
(B), transmission thread: conodonts have a trapezoidal, rectangular, and triangular-shaped, such as sawing.
A thread is a solid or the inner surface of the outer surface of the cross-section, a uniform shape protruding helix. According to their structural characteristics and uses can be divided into three categories:
(A), the general thread: for the triangular-shaped teeth for connecting or fastening parts. Common thread is divided into coarse teeth by the pitch and fine threads of two teeth, small teeth of the connecting thread a higher intensity.
(B), transmission thread: conodonts have a trapezoidal, rectangular, and triangular-shaped, such as sawing.
(C), sealing thread: for sealed connections, mainly useful thread, taper thread pipe thread and the cone.
Second, with the level of thread: Thread thread together with the rotation between the size of loose or tight, with the role of the hierarchy is the thread on the inside and outside the provisions of deviation and tolerance combinations.
Second, with the level of thread: Thread thread together with the rotation between the size of loose or tight, with the role of the hierarchy is the thread on the inside and outside the provisions of deviation and tolerance combinations.
(A), of a unified British thread, external thread threaded three grades: 1A, 2A and 3A level, there are three levels within the thread: 1B, 2B and 3B-class, all with the gap. The higher the rating figures, coupled with tightening. Thread in English, the deviation is only provided for 1A and 2A level, 3A-class bias to zero, and the 1A and 2A grade level, are equivalent to deviation. The smaller the number the greater the tolerance level, as shown: 1B 2B 3B Thread 3A basic outside diameter thread 2A 1A 1,1 A and 1B class, a very loose tolerance level, it applies to both inside and outside the thread with the Tolerance. 2,2 A and 2B class, is the British series of mechanical fasteners provides the most common thread tolerance level. 3,3 A and 3B level, rotating together with the formation of the tight, tight tolerances for fasteners for use in safety critical design. 4, external thread is, 1A and 2A there is a tie in with the tolerance level, 3A-class did not. 1A tolerance level tolerance level than 2A large 50%, more than 75% of large class 3A, for the internal thread, 2B than 2A tolerance level tolerance 30%. 1B-class than the 50 percent scale 2B, 3B scale than 75%.
(B), metric thread, external thread threaded three levels: 4h, 6h and 6g, there are three thread Thread rating: 5H, 6 H, 7H. (Standard thread on the accuracy level is divided into I, II, III levels, usually under conditions of class II) in the metric system in the thread, H and h the basic error of zero. G basic positive deviation, e, f and g of the basic bias is negative. As shown: GH tolerance deviations in the basic thread diameter fghe H outside the thread is commonly used within the thread tolerance zone position, generally not used as surface coating, or thin layer of phosphate. G location for special occasions, the basic bias, such as the thickness of the coating, generally little used. 2, g is used to plating of 6-9um thin coating, such as product drawings 6h bolt requirements, and its pre-plated thread of tolerance with the use of 6g. 3, into a thread with the best combination of H / g, H / h, or G / h, for bolts, nuts and other fine thread fasteners, standard recommended 6H/6g with.