|One, the structure characteristics and kinds of thread spike|
Thread is a solid outer surface or inner surface of cross section, a uniform spiral convex shape.
According to its structural characteristics and use can be divided into three categories:
(a) common thread: tooth shape to triangle, used to connect to or fastening parts.
Common thread according to the pitch is divided into two kinds of coarse thread and fine thread, fine thread connection strength is higher.
(2) the transmission thread: tooth shape with trapezoidal triangle, rectangle, saw and etc.
(3) sealing thread: used in sealing connection, mainly work thread, taper thread and taper pipe threads.
Second, the level of thread with:
Thread fit is the size of the screw thread and loose or tight, cooperate with the rank is the effect on the internal and external thread deviation and tolerance.
(a) with unified inch thread, the thread has three levels: 1 a, 2 a and 3 a, internal thread has three levels:
1 b, 2 b and 3 b, all of them are clearance fit.
Rating the higher the number, with tight.
In inch thread, the deviation provides only 1 a and 2 a, 3 a grade of zero deviation, and level 1 a and 2 a, deviations are equal.
The smaller the number, the greater the tolerance grade,
1, 1 a and 1 b, very loose tolerance grade, its applicable to internal and external thread tolerance to cooperate.
2, 2 a and 2 b, inch series of mechanical fasteners is the most common thread tolerance grade.
3, 3 a and 3 b, spin and form the tight fit, suitable for tolerance of fasteners, key design for safety.
4, external thread, 1 a and 2 a level have a fit tolerance, aaa.
Level 1 a tolerance of 50% larger than 2 a level of tolerance, 75% larger than aaa, internal threads, 2 b level of tolerance is larger than 2 a tolerance of 30%.
1 b 50% larger than 2 b, 75% larger than level 3 b.
(2) metric thread, thread has three levels: 4 h, 6 h and g, internal thread has three levels: 5 h, 6 h, 7 h.
(Japanese standard thread into Ⅰ, Ⅱ precision, Ⅲ level 3, usually situation as Ⅱ level) in the metric thread, H and H basic deviation is zero.
G the basic deviation of positive, e, f and G the basic deviation of negative.
1, H is internal threads commonly used tolerance zone position, is generally not used as surface coating, or use the extremely thin layer of phosphating.
G position basic deviation for special occasions, such as thicker coating, seldom used in general.
2, g are commonly used to plating 6-9 um thin coating, such as product drawing requirements is 6 h bolt, the thread USES 6 g tolerance zone before plating.
3, thread with the best combination into H/g, H/H or g/H, thread for a refined fasteners such as bolts, nuts, standard 6 H/g is recommended for the cooperation.
Standard referenceThe diameter of the typeSurface treatmentlevelThe raw materials
Electric galvanized etc.4.6
10.9Low carbon steel
Medium carbon steel
Alloy steelRail Fastening manufacturers