The tap drill size is the diameter of the hole that needs to be drilled before tapping. In order to find the right size, you need to know the thread count of the screw you're using. For example, a #10-24 screw has 24 threads per inch, so you would need to drill a #10 hole. There are a few different ways to measure tap drill size in the USA. The most common way is by using a standard chart, which can be found online or in many hardware stores. This chart lists the various diameters of taps and their corresponding drill bit sizes. Another way to determine tap drill size is by using a formula. This formula takes into account the threads per inch (TPI) of the tap. To use this method, first divide the TPI by 4. Then, add 0.005 to that number and subtract that from the major diameter of the tap (in inches). For example, let's say you're using a 1/4-20 tap. 20 TPI divided by 4 equals 5, plus 0.005 equals 5.005, minus 1/4 equals 0.755". This would be the correct size to drill for your tap in order to create threads that are tight and secure. Keep in mind that these formulas are generalities - there may be slight variations depending on the manufacturer or type of material you're working with. It's always best to consult a professional or experienced individual before beginning any project involving taps and drilling! Tap Drill Size in The USA - A Complete Chart. A tap drill chart is a table that shows the recommended tap drill sizes for various screw threads. The most common thread size in use today is the Unified Thread Standard (UTS), which is used in the United States, Canada, and Mexico. The UTS standardizes screw threads by diameter, pitch (the distance between each thread) and shape (either square or rounded). Inch Sizes (all measurements in inches) Tap Size and Pitch. Cutting Taps. Forming Taps. Drill Size. Decimal Equiv.Drill Size. Decimal Equiv.0-803/64.046954.05501-7253.059551.06702-5650.07005/64.07812-6450.070047.07853-4847.078543.08903-5646.08102.30.09054-4043.089038.10154-4842.09352.60.10245-4038.101533.11305-4437.10402.90.11426-3236.10651/8.12506-4033.11303.25.12808-3229.136025.14958-3629.136024.152010-2426.147011/64.171910-3221.159016.177012-2416.17708.199012-2815.18007.20101/4-207.20101.22801/4-283.213015/64.23405/16-18F.2570L.29005/16-24I.2720M.29503/8-165/16.3125S.34803/8-24Q.3320T.35807/16-14U.3680Y.40407/16-2025/64.3906Z.41301/2-1327/64.421915/32.46821/2-2029/64.453112.25.48239/16-1231/64.484417/32.53129/16-1833/64.515613.50.53155/8-1117/32.531214.75.58075/8-1837/64.578115.25.60043/4-1021/32.656245/64.70313/4-1611/16.687523/32.71887/8-949/64.7656.*.*7/8-1413/16.8125.*.*1-87/8.8750.*.*1-1259/64.9219.*.*1-1/8 - 763/64.9844.*.*1-1/8 - 121 3/641.0469.*.*1-1/4 - 71 7/641.1094.*.*1-1/4 - 121 11/641.1719.*.*1-3/8 - 61 7/321.2188.*.*1-3/8 - 121 19/641.2969.*.*1-1/2 - 61 11/321.3438.*.*1-1/2 - 121 27/641.4219.*.* Metric Sizes (measurements in millimeters and inches) Tap Size and Pitch mm. Cutting Taps. Forming Taps. Drill Size mm. Decimal Equiv. in. Drill Size mm/in. Decimal Equiv. in. M1.6 x 0.35 1.25 .0492 1.45 .0571 M1.8 x 0.35 1.45 .0571 1.65 .0650 M2 x 0.40 1.60 .0630 1.80 .0709 M2.2 x 0.45 1.75 .0689 2.00 .0787 M2.5 x 0.45 2.05 .0807 2.30 .0906 M3 x 0.50 2.50 .0984 7/64 .1094 M3.5 x 0.60 2.90 .1142 3.20 .1260 M4 x 0.70 3.30 .1299 3.70 .1476 M4.5 x 0.75 3.70 .1476 4.10 .1614 M5 x 0.80 4.20 .1654 14 .1820 M6 x 1.00 5.00 .1969 7/32 .2188 M7 x 1.00 6.00 .2362 F .2570 M8 x 1.25 6.70 .2638 7.40 .2913 M8 x 1.00 7.00 .2756 19/64 .2969 M10 x 1.50 8.50 .3346 U .3680 M10 x 1.25 8.70 .3425 9.40 .3701 M12 x 1.75 10.20 .4016 11.20 .4409 M12 x 1.25 10.80 .4252 11.50 .4528 M14 x 2.00 12.00 .4724 33/64 .5156 M16 x 2.00 14.00 .5512 19/32 .5938 M16 x 1.50 14.50 .5709 15.25 .6004 M18 x 2.50 15.50 .6102 39/64 .6094 M18 x 1.50 16.50 .6496 17.25 .6791 M20 x 2.50 17.50 .6890 * .* M20 x 1.50 18.50 .7283 * .* M22 x 2.50 19.50 .7677 * .* M22 x 1.50 20.50 .8071 * .* M24 x 3.00 21.00 .8268 * .* M24 x 2.00 22.00 .8661 * .* M27 x 3.00 24.00 .9449 * .* M27 x 2.00 25.00 .9843 * .* M30 x 3.50 26.50 1.0433 * .* M30 x 2.00 28.00 1.1024 * .* M33 x 3.50 29.50 1.1614 * .* M33 x 2.00 31.00 1.2205 * .* M36 x 4.00 32.00 1.2598 * .* M36 x 3.00 33.00 1.2992 * .* M39 x 4.00 35.00 1.3780 * .* M39 x 3.00 36.00 1.4173 * .* Pipe Tap Sizes (measurements in millimeters and inches) Nominal. NPT & NPTF. Pipe Tap Size Without Reamer With Reamer NPSM NPSC NPSF 1/16-27 C .242 A .234 — .250 D .246 1/8-27 Q .332 21/64 T .358 Q .332 R .339 1/4-18 7/16 27/64 15/32 7/16 7/16 3/8-18 9/16 9/16 .603 (special) 37/64 37/64 1/2-14 45/64 11/16 19 mm 18 mm 18 mm 3/4-14 29/32 57/64 61/64 59/64 59/64 1 – 11-1/2 1 9/64 1 1/8 1 13/64 1 5/32 1 5/32 1-1/4 –11-1/2 1 31/64 1 15/32 1 35/64 1 1/2 — 1-1/2 –11-1/2 1 23/32 1 45/64 1 25/32 1 47/64 — 2 – 11-1/2 2 3/16 2 11/64 2 1/4 2 13/64 — Tap Drill Size Calculator. When it comes to choosing the right size drill bit for your project, the tap drill size calculator is an essential tool. This helpful guide will ensure that you select the correct sized drill bit every time, making your projects go smoothly and without any issues. The first step is finding out the thread count of your screw or bolt. This is usually listed on the packaging. Once you know this number, divide it by 4 to get the tap drill size in inches. For example, if you have a 1/4-20 screw, the tap drill size would be .25/.20 = .125 inches. Now that you have the proper tap drill size, simply match it up with the corresponding chart below and find your perfect fit! -For a #4 screw: 5/32” tap drill -For a #6 screw: 3/16” tap drill Tap Drill Size PDF. What is a tap drill? A tap drill is a tool used to create threads in a workpiece by cutting a helical groove into the material. It consists of a cylindrical body with a cutting edge at one end and a handle at the other end. What is the tap drill used for? The tap drill is used to create internal threads in a workpiece, such as a hole in a piece of metal or plastic. It is used in conjunction with a tap handle, which is used to turn the tap drill and cut the threads. How do I determine the tap drill size for a given tap? There are several ways to determine the tap drill size for a given tap. One method is to consult a tap drill size chart, which lists the recommended tap drill sizes for various tap sizes and pitches. Another method is to use a tap and drill size calculator, which can be found online or in machinist handbooks. Are tap drill sizes the same in the USA as in other countries? Tap drill sizes can vary slightly between countries due to differences in tap and thread design standards. In the USA, tap drill sizes are typically based on the Unified Thread Standard (UTS), which is used for most industrial applications. Is it important to use the correct tap drill size? Yes, it is important to use the correct tap drill size when tapping a workpiece. Using the wrong tap drill size can result in a tap breaking or a thread that is too loose or too tight. It can also result in reduced thread strength and potentially even damage to the workpiece. Can I use a different tap drill size than the one recommended by the manufacturer? It is generally recommended to use the tap drill size recommended by the manufacturer, as it has been carefully calculated to produce the best results. However, in some cases, it may be necessary to use a slightly different tap drill size due to the specific requirements of the application. It is important to carefully consider the implications of using a different tap drill size and to consult with a knowledgeable machinist or engineer if in doubt. How do I choose the right tap drill? The right tap drill for your application will depend on the size and pitch of the tap you are using, as well as the material of the workpiece. It is important to consult a tap drill size chart or use a tap and drill size calculator to determine the appropriate tap drill size for your specific application. How do I use a tap drill? To use a tap drill, first drill a hole in the workpiece using a drill bit of the appropriate size. Next, attach the tap drill to a tap handle and insert the tap drill into the hole. Slowly turn the tap handle to cut the threads into the hole. It is important to use a light, consistent force and to periodically back the tap drill out of the hole to clear the chips. Are there different types of tap drills available? Yes, there are different types of tap drills available to suit different materials and threading applications. Some common types of tap drills include taper taps, plug taps, and bottoming taps. It is important to choose the right type of tap drill for your specific application to ensure the best results. Conclusion. Most people in the United States know what a standard drill bit is, but they may not be familiar with tap drill bits. A tap drill bit is a special type of drill bit that is used to create threads in a hole. This type of bit is used for both metal and woodworking applications. The most common sizes for tap drill bits are 1/4 inch, 3/8 inch, and 1/2 inch. These sizes can be found at most hardware stores.