Japanese Standard Thread Tolerance
Threads are a fundamental mechanical part used to join two components together. The most common thread type used in Japan is the “Japanese Standard Thread”. This thread type is an ISO metric thread, which means that it has a uniform size and pitch for each thread type. Though all threads, including Japanese Standard Thread, are designed to have a consistent size, there is an allowance for tolerance, or a margin of error in the fit of connecting components. The Japanese Standard Thread Tolerance is a set of limits that specify how much the actual size and pitch of a thread can vary from its nominal size.
The Japanese Standards Association (JSA) is responsible for establishing the Japanese Standard Thread Tolerance. This includes defining any limits of tolerance and specifying a measuring and inspection criteria for determining if a given thread meets tolerance requirements. In this article, we’ll review what the JSA specifies for Japanese Standard Thread Tolerance and discuss some of the implications it can have on the performance of threaded connections.
The Japanese Standard Thread Tolerance specifies the limits of deviation from the thread’s nominal size. In general, it can be broken down into two categories: Fit-in Tolerance and Fit-on Tolerance. Fit-in Tolerance specifies the tolerance in measuring the size of a given thread, and Fit-on Tolerance defines the tolerance for when two threads are connected. The main body of the Japanese Standard Thread Tolerance is the tables and figures that give the numerical values of tolerance limit.
The JSA specifies different limits of tolerance for external and internal threads, as well as classes of tolerance. Classification is based on the size of the thread and the expected use of the connection. For example, for a M12 thread, there are two classes, 2A (coarse) and 3A (fine). Coarse threads have larger tolerance limits than fine threads, so they can be used for looser connections.
The numerical values for the tolerance limits are based on the tolerance deviation from the nominal size. For each class and size of thread, there is a limit of divergence from the nominal size and pitch. The larger the divergence from the nominal size and pitch, the tighter the fit between two connecting parts. A tight fit guarantees the most reliable and secure connection, whereas a loose fit can lead to connection issues.
The Japanese Standard Thread Tolerance also specifies a measuring and inspection criteria for determining if a given thread meets tolerance requirements. The criteria include different geometric parameters, such as the angle and shape of the thread. The parameters are measured by a special tool, called a thread plug gauge, which is used to inspect the quality of a given thread. If a thread fails the inspection, it needs to be repaired or replaced to ensure that it meets the Japanese Standard Thread Tolerance.
In conclusion, the Japanese Standard Thread Tolerance is a set of limits that specify the limits of the divergence from the nominal size and pitch of a given thread. It is established by the JSA and specifies numerical values of tolerance limits as well as a measuring and inspection criteria for ensuring that threads meet tolerance requirements. Understanding the Japanese Standard Thread Tolerance can help ensure reliable and secure connections, as well as avoid connection issues due to tolerance deviations.
