drill and tap

Below is a comprehensive drill and tap size chart for all drills and taps, imperial and metric, up to 36.5 millimetres (1.44 in) in diameter.
In manufactured parts, holes with female screw threads are often needed; they accept male screws to facilitate the building and fastening of a finished assembly. One of the most common ways to produce such threaded holes is to drill a hole of appropriate size with a drill bit and then tap it with a tap. Each standard size of female screw thread has one or several corresponding drill bit sizes that are within the range of appropriate size—slightly larger than the minor diameter of the mating male thread, but smaller than its pitch and major diameters. Such an appropriately sized drill is called a tap drill for that size of thread, because it is a correct drill to be followed by the tap. Many thread sizes have several possible tap drills, because they yield threads of varying thread depth between 50% and 100%. Usually thread depths of 60% to 75% are desired.
People frequently use a chart such as this to determine the proper tap drill for a certain thread size or the proper tap for an existing hole.

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  1. K

    Gun smith for drill&tap near Marysville, wa?

    Looking to have a someone drill and tap 3 holes and mount rifle sights on a rem870, does anyone have any recommendations? I’ve gotten a few, but they’ve all turned up as dead ends. Located in Marysville, willing to travel within reason.
  2. K

    ISO gunsmith for drill and tap for rem 870

  3. Quartermaster

    Drilling and tapping in Portland

    Looking for a local gunsmith/machinist to drill and tap my Ruger 22/45 Lite for an under barrel accessory rail. Receiver is aluminum, and I'm not comfortable trying it myself with such fine threads.
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