Общий каталог OSG 2018 - 2019 - страница 650

Threading Terminology Tap and Screw Thread Terminology Allowance: The minimum clearance or maximum interference which is Pitch Diameter: On a straight screw thread, the diameter of an intended between mating parts. imaginary cylinder where the width of the thread and the width of the space between threads is equal. Angle of Thread: The angle included between the flanks of a thread measured in an axial plane. Point Diameter: The diameter at the leading end of the chamfered portion. Back Taper: A slight taper on the threaded portion of the tap, making the pitch diameter near the shank smaller than that at the chamfer. Radial: The straight face of a land, the plane of which passes through the axis of the tap. Basic: The theoretical or nominal standard size from which all variations are made. Rake: The angle of the cutting face of the land in relation to an axial plane intersecting the cutting face at the major diameter. Chamfer: The tapered and relieved cutting teeth at the front end of the threaded section. Common types of chamfer are taper, 8 to 10 Relief: The removal of metal behind the cutting edge to provide threads long, plug, 3 to 5 threads, semi (or modified) bottom = 2.5 clearance between the part being threaded and a portion of the - 3 threads and bottoming, 1-1/2 threads. threaded land. Also, see back taper. Crest: The top surface joining the two sides or flanks of a thread. Chamfer Relief: The gradual decrease in land height from cutting edge to heel on the chamfered portion of the tap land to provide radial Cutting Face: The leading side of the land. clearance for the cutting edge. Flute: The longitudinal channels formed on a tap to create cutting Con-eccentric Relief: Radial relief in the thread form starting back of a edges on the thread profile. concentric margin. Heel: The following side of the land. Eccentric Thread Relief: Radial relief in the thread form starting at the cutting edge and continuing to the heel. Height of Thread: In profile, distance between crest and bottom section of thread measured to the axis. Root: The bottom surface joining the flanks of two adjacent threads. Hook Face: A concave cutting face of the land. This may be varied Side or Flank Thread: The surface of the thread which connects the crest for different materials and conditions. to the root. Interrupted Thread: Alternate teeth are removed in the thread helix Shank: The portion of the tap by which it is held. on a tap having an odd number of flutes. Spiral Point: An oblique cutting edge ground into the lands to provide a Land: Threaded sections between the flutes of a tap. shear cutting action on the first few threads. Lead of Thread: The distance a screw thread advances axially in Square: The squared end of the tap shank by which the tap is driven. one turn. Thread: The helical formed portion of the tap which produces the pitch Major Diameter: The largest diameter of the screw or nut on a straight in a pre-existing hole. screw thread. Thread Lead Angle: The angle made by the helix of the thread at the Minor Diameter: The smallest diameter of the screw or nut on a straight pitch diameter, with a plane perpendicular to the axis. screw thread. Threads per Inch: The number of threads in one inch of length. Neck: The reduced diameter, on some taps, between the threaded portion and the shank. Thread: Single: A thread in which lead is equal to pitch. Pitch: The distance from a point on one thread to a corresponding point Double: A thread in which lead is equal to twice on the next thread, measured parallel to the axis. the pitch. Triple: A thread in which lead is equal to triple the pitch. 650 Threading Technical WWW.OSGTOOL.COM