20 Free Tap Drill Charts (PDF)

20 Free Tap Drill Charts (PDF)

High precision is a must-have in machining operations in today’s engineering industry. The modern-day design engineer utilizes up-to-date tap drill charts to machine threads and holes with great accuracy and efficiency. Determining the drill bits and taps to use is a taxing feat for every engineer. There are so many variables to consider before machining. We provide you with an all-in-one guide on the most recent charts, how to use them, and how to reduce the risk of thread failure. Let’s jump right in.

What Is A Tap Drill Chart?

A tap drill chart is a machinist’s must-have reference document that contains drill bit sizes, tap sizes, and their equivalent thread specifications that guide an engineer in fabricating threads and drill holes. Tap drill charts employ different measurement systems, including metric, wire gauge number, fractional, and letter. However, after conversion to their individual measuring systems, all charts generate the same measurements.

Tap Drill Charts Templates & Examples

Tap Drill Charts #01

Tap Drill Charts #02

Tap Drill Charts #03

Tap Drill Charts #04

Tap Drill Charts #05

Tap Drill Sizes For Fractional Size Threads


Auxiliary Systems Tap Drill Chart

Bolt Grades Torque Specs


Hole Sizes for Cut Tapping

Imperial Tap Drill Chart




Project Status Report


Tap & Drill Chart

Tap Drill & Thread Height Chart

tap drill chart 20

    How to Convert the Drill Bit Sizes

    You can convert drill bit sizes using elementary math. Take the screw or bolt size in millimeters and subtract its pitch value. Some screws have the letter M and a number representing the screw diameter. The number following sign x is the pitch. Once you subtract, you have your drill sizes. I.e., M12x1.5 is a screw with 1.5 pitch and 12 mm diameter. So in your calculations, you will do this: (12-1.5=10.5) mm.

    How to Use the Drill Chart

    A drill chart contains different columns that help you select the correct drill bit. Firstly, you need to identify the screw or bolt you are working on within standard or metric measurement. Then check the major diameter, which will aid you in calculating threads for fine or coarse threading.

    Check the corresponding thread count (TPI) to aid you in matching the appropriate tap drill size. In the adjacent column, match the size of the screw or bolt to the tap drill size. The chart has the decimal equivalent in inches if you want to use the inch system. The example below will help you better understand to use a drill chart.

    If you have an SAE 12-28 bolt, it indicates the bolt size is 12, and the TPI is 28. Once you have the appropriate size, match it to the corresponding tap drill size. It is that simple. Depending on the conversant systems, you can also convert from the metric to standard measurements systems.

    How to Read a Tap Drill Chart

    In a standard tap drill chart, the first column indicates the tap size of the standard drill sizes as a number. In metric size, the measurements are in millimeters and inches denoted by M, while in inch size charts, the measurements are in inches and usually fractional. The second column list the tap drill size of the drill diameter you need to use and the decimal equivalent. The third column lists the threads per inch, and drill bit size required.

    Tip: Check the measurements system, whether it is in metric or Inch size, to avoid confusion. Alternatively, you can purchase an inclusive chart to suit different clients’ needs.

    Some charts combine metric and Inch size systems in one chart; therefore, you may find more than three columns. However, the metric and size systems are easy to identify since they have unique color codes.


    What are the 5 types of drill bits?

    There are over 20 types of drill bits. The main types are twist, rivet, flat, center, Masonry, auger, countersinking, and hole saw drill bits.

    How do I know what size drill to tap?

    The rule of thumb for identifying tapping drills is to subtract the pitch from the diameter of the thread. For example, the tapping drill for an M5x0.75 thread is (5-0.75= 4.25) mm.

    What does the number on a drill bit mean?

    The numerical markings on the drill bit indicate the diameter of the bit. The markings are fractional, i.e., ¼ and in inches. Drill bit numbers help a machinist identify a particular drill for a specific hole.

    What do symbols on drill mean?

    The symbols on a drill are usually the hammer symbol, drill symbol, and number markings. The drill symbol indicates the settings you need to drill a hole and eliminate torque interference. While number markings show the speed, the chuck will rotate. The hammer symbol imparts some percussion vibration to the drill.

    What is the drill size for a 3/8-16 tap?

    Use a 5/16″ cutting tap drill or S drill size for forming taps. The equivalent in inches is 0.3125.

    What size drill bit do I use for a 6-32 tap?

    People use a 36 drill bit and a 35 bit commonly. However, use #35 drill bit size for cutting 6-32 taps and 1/8 for forming taps.

    What size is a number 7 drill bit?

    0.2010 inches. In the tap drill chart, read off #7 on the drill bit sizes to the equivalent size in inches. You can use the same technique for all other numbered drill bits.

    What size is drill F?

    Size F is a 6.53 mm drill, and 0.2570 inches is the decimal equivalent.

    What size is a number 8 drill bit?

    There are different dimensions for the number 8 drill bit. 0.3346 For 8.50 mm and 0.3425 for 8.70 mm drill bits.

    What size is the AK drill bit?

    AK drill bit is a range of drill bits from the A drill .234 and K .281. Therefore, you may use 5/32 or 11/64 drill bits depending on the holes.

    What is the most common drill bit size?

    The most common drill bit size is 9.53 mm. The 12.7 mm closely follows the 9.53 drill bit.

    What are the Gold drill bits for?

    Gold drill bits provide high resistance to heat buildup and deliver clean holes. Fabricators prefer gold bits due to their durability.

    What is the strongest drill bit?

    Titanium drill bits are harder than cobalt. However, titanium bits can’t be sharpened, unlike cobalt which makes cobalt the better option in the long run.


    To determine an accurate hole without reading from a tap drill chart is impossible for any machinist. Although many engineers have high precision, there is always room for improvement. Once you learn to read and use a tap drill chart, you will be the better engineer the world deserves.