What is the difference between Class 2 and Class 3 fasteners?
What is the difference between Class 2 and Class 3 fasteners? The Class of a thread indicates the tolerance allowed in manufacturing. Class 1 is a loose fit, Class 2 is a free fit, Class 3 is a medium fit, and Class 4 is a close fit. Aircraft bolts are almost always manufactured in the Class 3, medium fit.
Can you mix 2A and 3B threads?
The requirements for screw thread fits for specific application are predicated on end use and can be met by specifying the proper combinations of thread classes for the components. For example, a Class 2A external thread may be used with a Class 1B, 2B or 3B internal thread.
What is the tolerance of 2A and 3A?
The allowance is 30% of the class 2A tolerance. For class 3A, the major and pitch diameter maximums are at the basic size. Also, the pitch diameter tolerance for class 3A is 0.0035 inches, which is smaller than the class 2A tolerance of 0.0047 inches.
What is the difference between UNF 2A and UNF 3A?
Class 1A is a loose commercial fit for easy assembly and disassembly. Class 2A is a medium fit. Class 3A is a tight fit used where a closed fit between mating parts is required.