中文版Fastener measure knowledge
Now in the world the length Measuring unit mainly has two kinds, one kind is the metric system, the Measuring unit for the rice (m), the centimeter (cm), the millimeter (mm) and so on, in Southeast Asia uses and so on Europe, our country and Japan are many, another kind is the British system, the Measuring unit mainly for the inch (inch), is equal in our country old system's city inch, in European and American countries uses and so on US, Britain are many.
1st, metric measurement: (10 enter system)
1m =100 cm=1000 mm
1 cm
0 1 2 3 4 5 6 7 8 9 10 mm
2nd, British system measurement: (8 enter system)
1 inch =8 UK divides 1 inch =25.4 mm3/8￠￠×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
3rd, 1/4￠￠ the following product expresses its name diameter with the designation, for example:
4#, 5#, 6#, 7#, 8#, 10#, 12#
The second chapter thread
First, the thread is one kind in the solid outside surface or on the internal surface section, has the even spiral line bulge shape. May divide into three broad headings according to its unique feature and the use:
(one) plain thread: The tooth shape is a triangle, uses in connecting or the fastening parts. The plain thread divides into the coarse thread and the fine thread two kinds according to the pitch, the fine thread joint strength is high.
(two) transmission thread: The tooth shape has the trapezoid, the rectangle, the sawtooth and the triangle and so on.
(three) seals the thread: Uses in sealing the connection, is mainly is effective the thread, the awl thread and the awl pipe thread.
Second, thread grade of fit:
The thread coordination is turns on lathe gathers between the thread the pine or the tight size, the coordinate rank is the function in the inside and outside thread upper deviation and the common difference stipulation combination.
(one) to the unified inch thread, the external screw thread has three kind of thread ranks: 1A, 2A and the 3A level, the box thread has three ranks:
1B, 2B and the 3B level, is the clearance fit completely. The rank digit is higher, the coordination is tighter. In the inch thread, the deviation only stipulated that 1A and the 2A level, the 3A level's deviation is zero, moreover 1A and the 2A level's rank deviation is equal.
A rank number bigger common difference is smaller, like the chart shows:
1B 2B 3B box thread
Basic pitch diameter
3A external screw thread
2A
1A
1st, 1A and the 1B level, the very loose grade of tolerance, it is suitable for the inside and outside thread allowable deviation coordination.
2nd, 2A and the 2B level, is the British system series mechanical fastener stipulates the most general thread tolerance rank.
3rd, 3A and the 3B level, turns on lathe gathers forms the tightest coordination, is suitable in the common difference tight fastener, uses in the secure key design.
4th, the foreign thread, 1A and the 2A level has a tolerance on fit, the 3A level does not have. 1A level common difference compared to 2A level common difference big 50%, compared to the 3A level big 75%, the internal thread, the 2B level common difference compared to the 2A common difference big 30%. 1B level compared to the 2B level big 50%, compared to the 3B level big 75%.
