Unified (UN) screw threads are a standard form of thread used in the United States and other countries around the world. They are widely used in a variety of applications, including fasteners, machinery, and other equipment that requires secure and reliable threaded connections. The thread standard is defined in ANSI/ASME B1.1(2019). The UN thread system...
The nominal size is the basic major diameter of the designated thread. It can be specified as fractional diameter, screw number, or the decimal equivalent. The nominal size is interpreted a designation only, without dimensional significance beyond the designation. Refer to the standard for major diameter tolerance.
The number of threads per inch is related to the pitch, it is the inverse of the pitch. In the designation, it is nominal only, and does not indicate tolerance.
The Unified thread form is indicated with the UN or UNR symbol.
The thread series symbol in a Unified thread designation indicates the specific type and characteristics of the thread. This symbol helps identify the thread's design and intended application. Common thread series symbols include: UN: Unified , the general series used for both coarse and fine threads. UNR: Unified , requires rounded root. UNC: Unified Coarse,...
Thread classes define how much (if any) allowance is required between mating threads, and how large the tolerance zone is for the male and female threads. Since these values are different for internal and external threads, each class identifier (1, 2, or #) must include either an A or B to distinguish between external and internal thread limits. Class...
Because they are designed to be assembled together, thread dimensions are different for internal and external threads. To distinguish between the two, the letter A is used to designate external thread and B is used to indicate internal threads. The A or B symbol is actually part of the class symbol. See thread class.
Unless otherwise noted, all threads are right-handed. Use LH to indicated a left-hand thread.
Unified (UN) screw threads are a standard form of thread used in the United States and other countries...
The nominal size is the basic major diameter of the designated thread. It can be specified as fractional...
The number of threads per inch is related to the pitch , it is the inverse of the pitch. In the designation,...
The Unified thread form is indicated with the UN or UNR symbol.
The thread series symbol in a Unified thread designation indicates the specific type and characteristics...
In the Unified Thread Series, graded pitch series refer to the different classifications of thread pitches...
In the Unified Thread system, pitches are available which do not fall into the graded pitch series....
UNS threads represent unique combinations of diameter and pitch, adhering to the Unified Thread Standard...
Thread classes define how much (if any) allowance is required between mating threads, and how large t...
Because they are designed to be assembled together, thread dimensions are different for internal and...
