What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Slotted Round Head Wood Screws GB 99-86 Slotted Countersunk Head Wood Screws GB 100-86 Slotted Half Countersunk Head Wood Screws GB 101-86 Hexagon Head Wood Screws GB 102-86 Cross Recessed Round Head Wood Screws GB 950-86 Cross Slotted countersunk head wood screws GB 951-86 Cross recessed countersunk head wood screws GB 952-86
The performance grade 8.8 of stainless steel bolts refers to the material's tensile strength limit of 800MPa and yield limit of 640MPa. The performance grades of stainless steel bolts, studs and studs are divided into 10 grades: from 3.6 to 12.9. The number before the decimal point represents 1/100 of the tensile strength limit of the material, and the number after the decimal point represents 10 times the ratio of the material's yield limit to the tensile strength limit. There are 7 grades of performance grades for nuts, from 4 to 12. The numbers roughly represent 1/100 of the minimum stress that the stainless steel nut is guaranteed to withstand. For unified inch threads, there are three thread grades for external threads: grades 1A, 2A and 3A, and three grades for internal threads: grades 1B, 2B and 3B, all of which are clearance fits. The higher the rating number, the tighter the fit. Classes 1, 1A and 1B, very loose tolerance classes, which are suitable for tolerance fits of internal and external threads. Grades 2, 2A and 2B are the most common thread tolerance grades specified for inch series mechanical stainless steel fasteners. Grades 3, 3A and 3B, screwed together to form the tightest fit, suitable for tight tolerance stainless steel standard parts, for safety critical designs. Metric threads, there are three thread grades for external threads: 4h, 6h and 6g, and three thread grades for internal threads: 5H, 6H, 7H. Thread fit is best combined into H/g, H/h or G/h. For bolts, stainless steel nuts and other refined fastener threads, the standard recommends 6H/6g fit. Carbon steel: The strength grade is marked by ? It consists of two separated numbers. The meaning of the number part before the ? in the marking code represents the nominal tensile strength, for example, 4 in grade 4.8 represents 1/100 of the nominal tensile strength of 400N/MM2. The meaning of the ? and the number part after the point in the marking code represents the yield-strength ratio, that is, the ratio of the nominal yield point or the nominal yield strength to the nominal tensile strength. For example, the yield point of grade 4.8 products is 320N/mm2. The strength grade mark of stainless steel products consists of two parts separated by —. The symbol before — in the sign code indicates the material. Such as: A2, A4 and other signs — indicate strength, such as: A2-70 Carbon steel: The mechanical properties of bolts can be divided into: 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9 in total 10 performance levels
As shown in FIG. 1 and FIG. 2 , a rivet die in the prior art includes a set of top die 1 and cover die 2 arranged opposite to each other. The top die 1 is provided with a cavity 1 in the center that matches the shape of the rivet dome head 3-1. -1, the center of the cover mold 2 is provided with a mold cavity 2-1 that matches the shape of the rivet dome head 3-3.
At present, the connecting shafts of commonly used food processing knives on the market generally use square bayonet, which is not easy to install parts, and it is time-consuming and laborious when replacing parts; Increased processing costs. There is also a link structure with a circular bayonet on the market, but it is easy to loosen and not firm after the entire food processor is used for a period of time, which affects the use of the machine. Therefore, a connection structure that is easy to operate and simple to process is urgently needed.
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