Tap drill chart iso#
Tap drill chart series#

Unified threads specify density in threads per inch, while Metric threads specify the thread pitch.

Tap drill chart series#

Thread series are denoted by the major diameter and density of threads. Most screws are identified by their thread series. Those forms which are not standardized by the Unified screw thread system are designated UNS. For example, an extremely fine thread with a flat root contour is designated UNEF. These can be further described by appending more letters. There are many thread forms in the Unified screw thread standard designated by either UN, which defines a flat root contour, or UNR, which defines a round root contour.

Tap drill chart iso#

Common thread forms include the Unified Screw Thread Form, used in the United States of America and measured in imperial units, and the ISO Metric Screw Thread Form, used in many parts of the world and measured with the International System of Units. The pitch diameter is approximately halfway between the major and minor diameters.ДЄ thread form is a set of rules that define the features' scale relative to one another. For most screws, crests and roots do not terminate at a sharp point, so crest and root truncation values are included in the definitions of major and minor diameter. The major diameter is taken from the crests of a thread while the minor diameter is taken from the roots. Each feature is shown in the diagram to the right. Unless otherwise stated, threads have a flank angle of 30В°, resulting in a total angle between flanks of 60В°. The flank angle is defined as the angle the flank makes with a perpendicular ray drawn from the screw axis. The distance between corresponding points on adjacent threads is known as the pitch of the thread. Except in special cases, threads have symmetrical sides inclined at equal angles when a vertical line is drawn through the center of a crest or root. For more details regarding specifications and dimensions, please consult the Machinery's Handbook, available for purchase at many bookstores.ДЄ thread consists of three repeating features: a crest, flank, and root (see drawing to the right). The following is a general overview of screw threading. Click to Enlarge Threading Specifications