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Free Printable Tap Drill Size Chart [PDF] Metric, Inch, NPT

    Like most DIY’ers and other handypersons, you probably encounter projects where you need to use a drill and tap. Tap drill charts are few and far between, and it often takes hours of searching to find them. This is mainly because there are many different measurements of how the units interact with one another that was created over half a dozen centuries ago.

    What is Tap Drill Chart?

    Tap Drill Chart
    Tap Drill Chart

    Tap Drill Chart: This is an example chart you can use to find the size of the tap drill you need to make your female thread. It is not the only way of doing it. Men and women have been fighting over it since the dawn of time. Chances are, this will be the last written guideline ever.

    Tap Drill Chart Templates

    Drill Size Conversion Chart

    Drill bit sizes and tap dimensions depend on the type of screws that you are using. For example, there are standard drill bit sizes and tap sizes, metric equivalents, and different metal types or even alloys. You need to know what it is to determine what you need fully. You risk stripping your screw or drilling too deep a hole, ruining it entirely if you don’t.

    When you are following the metric system, especially when dealing with production machinery, you will regularly require threading a whole. Threading as a whole is also referred to as tapping, and it’s a process of preparing an internal thread in a hole that was previously drilled into a piece of metal. The hole is first drilled with a steel cutting tap, after which it is then cleaned out with taps and dies that are ideal for removing chips and burrs. Afterward, the hole will be threaded with the right tap so that that female threaded parts can be screwed into it.

    For Imperial (inch) threads the tapping drill size is calculated in the same way, diameter minus pitch. eg for 3/4.10 UNC pitch = 0.1, diameter = 0.75, tapping drill = 0.65 = 16.5mm.

    How to Use the Drill Tap Wall Chart 

    Ever wonder how drill and tap charts work? In this post, we’ll find out. To understand what makes up a drill and tap chart, let’s first see how the combination of these two tools falls short on their own when it comes to creating female screw tips. Drill bits have to be the right size for a hole.

    That is all that goes into making up the tap of the drill itself. In the case of wood screws, they have a set width. To make the hole of appropriate length and diameters, you have to drill them out first with a particular sized bit. This is what makes up the ‘tap’ in your drill set.

    These charts should be used to make quick drill guides when the size of the drill bit is not known. The sizes range between 5 mm and 57.5 mm and are based on the inside diameter. To use these charts, all you need to know is the exact size of your dia (inside drill bit) minus 1mm then, use the chart on either side of the dia to create your guide. These charts contain hole diameters and hole depths for a variety of metals. While these charts are essential for fabricating accurate measurement tools, they can also be used as wall charts when making quick drill guides for your drill bit holder. For example, you might really need that five-eighths inch hole for your fastener, but you’re trying to match up a 3/8-inch tapping drill. If this is the case, check out your chart to see what drill size would be closest to achieving that five-eighths inch hole.

    How to Read a Tap Drill Chart

    A tap chart or a T-chart is a popular tool to quickly identify the right drill and tap size combination, usually based on a fractional drill size. A typical chart lists drill and tap sizes depicted in fractional numbers (1/16, 1/8, etc.), but it can be used to get a close approximation using letter and decimal equivalents as well. The number of threads per inch will be on the left side of the chart (TPI).

    The higher the number, the bigger the threads or, the smaller the cutters will be needed. You can find the diameter and then the index of taps and dies on the right. This index will list all possible answers directly next to each other. To use this tool, select your cutting instrument and then decide what kind of material you will use for cutting: mild steel, stainless steel, or alloy taps, for example. Then look up your answer on the charts below.


    What size drill do I need for a tap?

    To determine the drill size needed for a tap, you can refer to a tap drill chart. This chart shows the recommended drill bit size for each tap size. Generally, the drill size will be smaller than the tap diameter to allow the tap to cut threads into the hole.

    What are the common tap sizes?

    Some of the most common tap sizes include:
    Metric taps – M3, M4, M5, M6, M8, M10, M12
    UNC/UNF taps – #4, #6, #8, #10, 1/4″, 5/16″, 3/8″, 1/2″
    NPT pipe taps – 1/8″ NPT, 1/4″ NPT, 3/8″ NPT, 1/2″ NPT

    What is a tap drill chart?

    A tap drill chart displays the recommended drill bit size for each diameter and thread pitch of tap. For example, for a 1/4″-20 tap, the drill size would be 7/16″. The chart accounts for the 75% thread depth needed for the tap. Different charts are available for metric, UNC, UNF, and NPT taps.

    What size hole do you drill for a 1/2″ tap?

    For a 1/2″ tap, the recommended drill size is usually 21/64″ or 33mm. This allows the 1/2″ tap to cut threads approximately 0.014″ deep into the hole with a 75% thread depth. Always refer to a tap drill chart for the exact drill bit size needed for the tap’s thread pitch. Drilling the properly sized hole is key to tapping success.

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    Betina Jessen

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