As per the ISO metric screw thread standard, the thread depth should be 0.614 x pitch, which is why a smaller pitch number also results in a lower thread depth value. Now engineers can sit down and manually calculate the right tap drill. Or they can consult a tap drill chart like those found in the next section. Holding the level and square to the material turn the tap wrench until the first cut into the material has been made.

Below is a comprehensive drill and tap size chart for all drills and taps, imperial and metric, up to 36.5 millimetres (1.44in) in diameter. The tap drill size for the M10 1.5 pitch is 8.5 mm. This is the size of the hole that will be created when using a tap with this drilling speed. It is important to note that this number will change depending on the specific tool being used and the type of metal being drilled. For example, stainless steel [ 1] will require a different size tap drill than carbon steel. Conclusion Example (metric fine): For M7.0×0.5, major minus pitch yields 6.5, which at 92.9% happens to be an example that pushes over the outer bound of the 90% ± 2 pp, but major minus pitch is still valid, although smaller drills (6.3mm, 1⁄ 4, 6.4mm) will work well. a b c d e "NC, NF, NEF to one inch in diameter". Sizes.com. Archived from the original on 29 September 2006 . Retrieved 1 September 2006. {{ cite web}}: External link in |work= ( help)Some prefer to use somewhat arbitrary but reliable formulas like: “Dtap = Nominal Diameter – Thread Pitch”. This formula works for both metric and imperial units, and for all 60-degree threads (all ISO, DIN, UTS, UNC, UNS, and UNF bolts). The first tap drill chart below is in mm and the next in inches. Both are available as a printable tap drill chart PDF as well. Tap Drill Chart (mm and inches) The following chart describes how to determine the size of unified male threads when making a bolt or threaded pipe.

Example (inch, fine): For 7⁄ 16-20 (same diameter as the previous example, but this time with 20 threads per inch, which is considered fine), 0.437 in × 0.90 = 0.393 in (i.e., if the threads are to be fine, then a slightly larger diameter drill bit should be used before tapping the hole for the screw). High performance taps" (PDF). guhring.com . Retrieved 7 October 2010. {{ cite web}}: External link in |publisher= ( help) The table below shows the drill hole sizes for standard metric (coarse) threads and metric fine threads. Metric & Metric Fine Tap Drill Chart Ø The major minus pitch also works for inch-based threads, but you must first determine the pitch by looking at the number of treads per inch (TPI; for example, 1⁄ 20 = 0.050 and 1⁄ 13 ≈ 0.077), and your result will only land near a tap drill size (not directly on one).

Step by step External Threads on Rods (Using a Die)

For both of these rules of thumb (85%/90% and major minus pitch), the tap drill size yielded is not necessarily the only possible one, but it is a good one for general use. The “M” indicates the “metric diameter” of its thread (see tap drill chart below), which in our case is 4 mm. The second number (0.7) is the pitch which corresponds to the distance between two adjacent threads in millimeters. Finally, 20 is the length of the bolt in mm, measured from the tip of the thread to the bottom of the head (with the exception of oval headed bolts). a b c d e "Tap Drill Sizes". widell.com. Archived from the original on 14 November 2006 . Retrieved 1 September 2006. {{ cite web}}: External link in |work= ( help)