What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
In a traditional spring mattress, there are two layers of spring pads that are independent of each other. The manufacturing process of this kind of mattress is complicated, time-consuming and material-consuming, and after long-term use, the springs in the two-layer independent spring cushion are prone to translocation, which deforms the mattress and affects people's sleep.
Among the mold parts used in the can manufacturing industry, some product inner holes need to be processed with stop slots after heat treatment. The inner hole diameter of the product is φ28mm, the width of the slot is about 1.3mm, and the size and shape of the outer end face of the slot adjacent to the orifice The tolerance requirements are very strict, generally within the range of 0.02mm. If the CNC machine tool is used for cutting, the blade loss is very serious because the groove width is too narrow; if the inner hole grinding is used, there is no ready-made grinder and grinding wheel.
NPT, PT, G are all pipe threads. NPT is the abbreviation of National (American) Pipe Thread, which belongs to the American standard 60-degree taper pipe thread, which is used in North America. National standards can be found in GB/T12716-1991 PT is the abbreviation of Pipe Thread, which is a 55-degree sealed conical pipe thread, which belongs to the Whitworth thread family and is mostly used in Europe and the Commonwealth of Nations. Commonly used in water and gas pipe industry, the taper is specified as 1:16. The national standard can be found in GB/T7306-2000 G is a 55 degree non-threaded sealing pipe thread, which belongs to the Whitworth thread family. Marked as G stands for cylindrical thread. National standards can be found in GB/T7307-2001 In addition, the 1/4, 1/2, 1/8 marks in the thread refer to the diameter of the pipe, and the unit is inches. People in the industry usually refer to thread size in points, 1 inch equals 8 points, 1/4 inch is 2 points, and so on. G seems to be the general name for pipe threads (Guan), and the division of 55 and 60 degrees is functional, commonly known as pipe circle. That is, the thread is machined from a cylindrical surface. ZG is commonly known as pipe cone, that is, the thread is made of a conical surface. The general water pipe joints are like this. Rc means conical internal thread ZG means taper pipe thread, 3/4 means inch mark, which is 3/4 inch conical pipe Thread, there is in the Hardware Manual. The national standard stipulates that the major diameter of ZG 3/4 thread is 26.44 mm. Please refer to Metric, American and British Thread Standard Manual (Third Edition). Its representation method should be: ZG 3 /4″. Among them (〃) is the representative symbol for inches. One inch is equal to 8 inches. The origin of 3/4 is 6/8=3/4. Commonly known as 6 points. Similarly, the major diameter of ZG 1/2″ thread≈21 mm. Commonly known as 4 points. ZG 1″ thread diameter ≈ 33 mm. Commonly known as 1 inch. ZG 1 1/2″ thread pipe outer diameter ≈ 48 mm. Commonly known as 1 inch and a half. Taper pipe thread is very similar to pipe thread, the difference is Only in the taper. Note that the basic size of the pipe thread and ordinary thread is different. DN is the nominal diameter
Some heavy equipment such as large motors, large reducers, etc., in order to facilitate the installation and adjustment of equipment and the need for maintenance space, a certain position needs to be moved during equipment installation and maintenance. Usually, a steel base or platform is set under the equipment, and the base or The platform is provided with an oblong bolt installation slot, commonly known as an oblong slot, as shown in Figure 1--Figure 4. When using common hexagon head bolts or common T-bolts with the long circular groove in Figures 1 and 2, auxiliary fixing bolts or welding stoppers are required on the back of the long circular groove to prevent the bolt from rotating when the nut is tightened. In Fig. 3 and Fig. 4, the long circular groove itself has a clamping groove to prevent the rotation of the bolt, but this structure greatly increases the processing cost of the long circular groove.
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