1¼” NPT taps need a 1 1/2 inches size drill bit and can be used for re-threading damaged pipe threads. They’re mostly used for tapping fittings and couplings much like the 1/8″ 716" HSS Black & Gold KFD Split Point Jobber Length Drill Bit. KFD Killer Force Drill Bits are manufactured from M2 premium grade high speed steel. For use in a wide range of materials such aluminum, iron and stainless steel; 135° split point tip for fast penetration and accurate drilling; Round shank for use in a wide range of tool holding HelicoilDrill Chart. The minimum drilling depths shown below allow for the following recommended practices: Countersinking the drilled hole to prevent a feather edge at the start of the tapped hole. 3/4 - 1-1/2 pitch of insert "set down" to allow for maximum production tolerance. Dimensions are shown for both plug and bottoming taps. For plug ANSIB1.20.1 - NPT - American National Standard Taper Pipe Threads NPT and NPTF pipe threads - dimensions according ANSI/ASME B. British Standard Brass ANSIB1.20.1 - NPT - American National Standard Taper Pipe Threads NPT and NPTF pipe threads - dimensions according ANSI/ASME B. British Standard Brass Threads British Brass Thread is an imperial unit based screw thread. British Standard Cycle Threads British Standard Cycle is a British Imperial screw thread standard. Thispage provided the thread dimensions of 1/2 - 14 NPTF; NPTF stands for National Pipe Thread Fuel, based on ASTM B1.20.3. It is also called Dryseal Pipe Thread. It is a variation of the more popular NPT thread standard based on ASTM B1.20.1. Learn more about NPTF and the difference between NPTF and NPT; 1/2 - 14 NPTF - External Basic Thread BSPTRc 1/8 : Brith Pipe (BSP) Thread Dimensions and Tolerances. All the relevant data for this tread in one spot. Dryseal Pipe Threads (NPTF) British Pipe Threads (BSP) ACME Trapezoidal Threads; Minimum length of useful threads (L min) 4.5 : 0.1772 : Tap Drill Size (T d) 8.4 : 0.3307 : Browse Ads-Free For Just 1.5$ / Month. Login Choosefrom our selection of pipe thread repair inserts in a wide range of styles and sizes. In stock and ready to ship. Drill Bit Size: For Max. Hole Dia. Pkg. Qty. 1/4. 0.394" 33/64 " 33/64 " 12: Drill Bit, Through-Hole Tap, Installation Thefinal drill size of 1 8 is .125. This is because the decimal part of the number, 0.125, represents the diameter of the bit in inches. When looking at drill bits, the smaller the number, the smaller the bit. So a 1 8 bit is smaller than a 48 NPT : Pipe and Fitting Thread Dimensions and Tolerances. All the relevant data for this tread in one spot. 4-8 NPT : Pipe and Fitting Thread Dimensions and Tolerances. 4.31875: 109.696: Tap Drill Size (T) N/A: N/A: 4-8 NPT - Internal (Fitting) Drawing. Overview Drawing. Profile Drawing. 4-8 NPT - Tolerances. Property Minimum Maximum; wnJx4W.