helix angle.pdf

02D Th re ad In se rts Ex te rn al Ho lde r In te rn al Ho lde r Th re ad in g Technical Information for Threading πX Pitch diamiter(D) Helix angle(β) Lead(L) Technical Information for Threading ■ Special Features Ve rtic al T ype Ho lde r External Thread Internal Thread A thread on the internal surface of a cylinder or cone. External Thread A thread on the external surface of a cylinder screw or cone. Major Diameter The largest diameter of a screw thread. Depth of Thread The distance between the crest and root measured from normal to the axis. Pitch The distance between the corresponding points on adjacent thread forms measured parallel to the axis. This distance can be defined in millimeters or by the tpi (threads per inch), which is the reciprocal of the pitch. Helix Angle For a straight thread, where the lead of the thread and the pitch diameter circle circumference form a right angled triangle, the helix angle is the angle opposite of the lead. Straight Thread A thread formed on a cylinder. Taper Thread A thread formed on a cone. Nominal Diameter The diameter of which the diameter limits are derived by the application of deviation allowances and tolerances. Pitch Diameter On a straight thread, the diameter of an imaginary cylinder, the surface of which cuts the thread forms where the width of the thread and groove are equal. Minor Diameter The smallest diameter of a screw thread. A thread which, when viewed axially, winds in a counterclockwise and receding direction. All left-hand threads are designated LH. For a straight thread, where the lead of the thread and the pitch diameter circle circumference form a right angled triangle, the helix angle is the angle opposite of the lead. A thread which, when viewed axially, winds in a clockwise and receding direction. Threads are always right-hand unless they are specified. Major ? Pitch ? Minor? Pitch Helix Angle Thread Angle Root Crest ●Left-hand thread The V partial profile insert cuts without topping the