Screw Thread Definitions Major diameter The largest diameter of a straight screw thread This applies to both internal and external threads Pitch di

Screw Thread Definitions Major diameter The largest diameter of a straight screw thread. This applies to both internal and external threads. Pitch diameter On a straight thread, it is the diameter which passes through the thread profiles at such points which make the thread width of the groove equal to one-half of the basic pitch. On a perfect thread, this occurs at the point where the widths of the thread and groove are equal. 3. Thread angle (included) The included angle between the individual flanks of the thread form. 4. Minor diameter The smallest diameter of a straight screw thread. This applies to both internal and external threads. 5. Lead angle On a straight thread, the lead angle is the angle created by the helix of the thread at the pitch diameter with a plane perpendicular to the axis. 6. Lead The distance a screw thread advances axially in one revolution. On a single start, the pitch and lead are identical. The lead is equal to the pitch times the number of starts. 7. Pitch The distance from a point on a screw thread to a corresponding point on the next thread measured parallel to the thread axis. 8. Crest The outer most surface of the thread form which joins the flanks. 9. Root The inner most surface of the thread form which joins the flanks. nut major diameter pitch diameter minor diameter thread angle included pitch lead angle lead NOTE Threads per inch (TPI) not shown The number of threads per inch measured axially. The terms pitch and TPI are often used interchangeably. TPI 1/pitch Technical Information Widia Screw Thread Definitions resultant angle 3.5° 2.5° 1.5° 0.5° -0.5° -1.5° insert size (iC) toolholder shim ordering code 16mm ex. RH/in. LH ex. LH/in. RH SM-YE3-2P SM-YI3-2P SM-YE3-1P SM-YI3-1P SM-YE3 SM-YI3 SM-YE3-1N SM-YI3-1N SM-YE3-2N SM-YI3-2N SM-YE3-3N SM-YI3-3N 22mm ex. RH/in. LH ex. LH/in. RH SM-YE4-2P SM-YI4-2P SM-YE4-1P SM-YI4-1P SM-YE4 SM-YI4 SM-YE4-1N SM-YI4-1N SM-YE4-2N SM-YI4-2N SM-YE4-3N SM-YI4-3N Slanted Shim Kit Because you might occasionally need different shims than those supplied with our standard toolholders, we strongly recommend that shim kits be readily available in every tool shop. insert size shim size (D) ordering code contains slanted shims 3x 16mm ABY3 SM-YE3-2P, 1P, 1N, 2N, 3N SM-YI3-2P, 1P, 1N, 2N, 3N 4x 22mm ABY4 SM-YE4-2P, 1P, 1N, 2N, 3N SM-YI4-2P, 1P, 1N, 2N, 3N