RAD Torque Presents: Metric Stud Bolt To Nut Size Chart

NOMINAL DIAMETER (NOMINAL BOLT DIAMETER)
The diameter equal to the external diameter of the threads or the overall diameter of the part. (Nominal diameter is more of a label than a size. For example, a bolt and nut may be described as being ½” diameter. But neither the external threads of the bolt nor the internal threads of the nut are exactly .500 in diameter. In fact, the bolt diameter is a little smaller and the nut diameter a little larger. But it is easier to specify the components by a single size designation since the bolt and nut are mating components.)

PITCH (THREAD PITCH)
Pitch is the distance from the crest of one thread to the next or the distance from one thread groove to the next, measured from crest to crest. Pitch is also described as the number of threads per inch.

DIAMETER (BODY DIAMETER)
The smallest or largest pitch diameter that fits onto a screw or into a nut, including all of the form deviations such as lead, thread angle, taper, and roundness. Functional diameter is a measure of the ability to assemble the thread.

THREAD (BOLT THREADS)
A raised, helical rib or ridge around the interior or exterior of a cylindrically shaped object. Threads are found on screws, nuts, and bolts.

THREADS PER INCH
The decimal equivalent of the number of threads in an inch.

COARSE THREADS & FINE THREADS
Coarse threads are those with larger pitch (fewer threads per axial distance), and fine threads are those with smaller pitch (more threads per axial distance). Coarse threads have a larger threadform relative to screw diameter, whereas fine threads have a smaller threadform relative to screw diameter.

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