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Drill Size Chart and Tap Size Chart


The drill bit is typically rotated at high speeds and pressed into the material to remove material and form the hole. The size of the drill bit is chosen based on the desired hole diameter.Tapping is the process of creating internal threads inside a drilled hole. A tap is used, which is a cutting tool with threads that match the desired thread type and size. The tap is rotated and pressed into the hole, cutting into the material to form the threads. Taps come in different sizes and thread types to match specific requirements. When it comes to the selection of drill bit sizes and tap sizes, there are standard drill and tap size chart for reference.

What is the Drill and Tap Size Chart?


A drill and tap size chart is a reference guide that provides information on the recommended drill bit size and tap size for specific thread types and diameters. It helps in selecting the appropriate tools for drilling holes and creating threads during machining or assembly processes.

Drill Size Chart and Tap Size Chart

The chart typically consists of a table or grid format, with columns representing different thread sizes or types, and rows indicating the corresponding drill bit and tap sizes. The drill bit size is specified in terms of diameter, while the tap size may include information about the thread type, pitch, and diameter.

The purpose of a drill and tap size chart is to ensure that the drilled holes and threads are compatible and properly sized for secure and accurate fastening. It assists in selecting the correct drill bit size to create a hole with the appropriate diameter to accommodate the desired thread size. The recommended tap size ensures that the internal threads are correctly formed to match the corresponding external thread.

By referring to the chart, engineers, machinists, or fabricators can quickly identify the appropriate drill bit and tap sizes for a specific thread size or type. This saves time, promotes accuracy, and helps ensure proper fit and functionality of threaded connections.

It’s important to note that drill and tap size charts are based on industry standards and common practices. However, specific applications may have unique requirements, such as special thread forms, materials, or tolerance specifications. In such cases, it’s recommended to consult relevant standards, engineering references, or seek expert advice for accurate drill and tap size selections.

Why To Use Drill and Tap Size Chart?


A drill and tap size chart provides a reference guide for selecting the appropriate drill bit size and tap size when performing drilling and tapping operations. It lists the corresponding sizes for various thread types and diameters, helping to ensure proper hole preparation and thread creation.

Here’s why drill and tap size charts are useful:

  • Size selection: The chart helps in selecting the correct drill bit size for drilling the hole to accommodate the desired thread size. It provides the recommended drill bit diameter based on the thread type and size, ensuring a proper fit for the tap.
  • Thread compatibility: Different thread types, such as UNC (Unified National Coarse), UNF (Unified National Fine), or metric threads, require specific tap sizes. The chart indicates the appropriate tap size for the corresponding thread type and diameter, ensuring compatibility and proper thread engagement.
  • Accuracy and efficiency: Using the recommended drill bit and tap sizes ensures accuracy and efficiency in the drilling and tapping process. It helps avoid issues such as oversized or undersized holes or threads, which can lead to poor thread engagement, weakened connections, or thread stripping.
  • Standardization: Drill and tap size charts are based on industry standards and commonly used thread sizes. They provide a standardized reference, allowing engineers, machinists, and fabricators to communicate and work with consistent thread sizes and hole preparations.
  • Time and cost savings: By using a drill and tap size chart, you can quickly identify the appropriate sizes for your desired thread type and diameter. This saves time in the planning and preparation stages, reducing the risk of errors and the need for rework. It also helps in selecting the right tools, reducing the chance of tool breakage or damage.

Remember, while drill and tap size charts provide general guidelines, specific applications may have unique requirements. It’s important to consider factors such as material type, thread engagement requirements, and tolerance specifications when selecting drill bit and tap sizes. Always refer to appropriate industry standards, engineering references, or consult with experts for accurate drill and tap size requirements for your specific application.

The Types of Drill Bit Sizes


  • Fractional Inch Sizes: Fractional inch sizes are commonly used in the United States and are represented in inches. Examples include 1/16″, 1/8″, 3/16″, 1/4″, 3/8″, 1/2″, etc. Fractional inch drill bits are often used for general drilling applications.
  • Numbered Sizes: Numbered drill bit sizes are represented by a number, such as #1, #2, #3, and so on. These sizes are typically used for specific applications, such as tapping or screw clearance holes.
  • Letter Sizes: Letter sizes are represented by letters of the alphabet, starting from A and going up to Z. Examples include A, B, C, D, E, F, etc. Letter sizes are often used for specific applications where precise hole sizes are required.
  • Metric Sizes: Metric drill bit sizes are commonly used in countries that follow the metric system. They are represented in millimeters (mm). Examples include 2mm, 5mm, 10mm, etc. Metric drill bits are widely used in industries that follow metric measurements.
  • Wire Gauge Sizes: Wire gauge drill bit sizes are based on the American Wire Gauge (AWG) system. These sizes are commonly used for drilling holes to accommodate wire sizes or for electrical applications.
  • Step Drill Bits: Step drill bits have multiple stepped sizes within a single bit, allowing for drilling different hole diameters without the need for changing bits.

List of Drill and Tap Sizes


1.Drill Bit Sizes (Metric)

Here is an expanded drill bit sizes chart that includes both metric and imperial measurements, ranging from 0.05mm to 38mm:

Drill Bit Size (mm)Drill Bit Size (inch)
0.050.0020
0.10.0039
0.20.0079
0.30.0118
0.40.0157
0.50.0197
0.60.0236
0.70.0276
0.80.0315
0.90.0354
1.00.0394
1.10.0433
1.20.0472
1.30.0512
1.40.0551
1.50.0591
1.60.0630
1.70.0670
1.80.0709
1.90.0748
2.00.0787
2.50.0984
3.00.1181
3.50.1378
4.00.1575
4.50.1772
5.00.1969
5.50.2165
6.00.2362
6.50.2559
7.00.2756
7.50.2953
Drill Bit Size (mm)Drill Bit Size (inch)
8.00.3150
8.50.3346
9.00.3543
9.50.3740
10.00.3937
10.50.4134
11.00.4331
11.50.4528
12.00.4724
12.50.4921
13.00.5118
13.50.5315
14.00.5512
14.50.5709
15.00.5906
15.50.6102
16.00.6299
16.50.6496
17.00.6693
17.50.6890
18.00.7087
18.50.7283
19.00.7480
19.50.7677
20.00.7874
20.50.8071
21.00.8268
21.50.8465
22.00.8661
22.50.8858
23.00.9055
Drill Bit Size (mm)Drill Bit Size (inch)
23.50.9252
24.00.9449
24.50.9646
25.00.9843
25.51.004
26.01.024
26.51.043
27.01.063
27.51.083
28.01.102
28.51.122
29.01.142
29.51.161
30.01.181
30.51.201
31.01.220
31.51.240
32.01.260
32.51.279
33.01.299
33.51.319
34.01.338
34.51.358
35.01.378
35.51.397
36.01.417
36.51.437
37.01.457
37.51.476
38.01.496

2.Drill Bit Sizes (English)

Drill Bit Size (inch)Drill Bit Size (fraction)Drill Bit Size (decimal)
1/641/640.0156
1/321/320.0313
3/643/640.0469
1/161/160.0625
5/645/640.0781
3/323/320.0938
7/647/640.1094
1/81/80.1250
9/649/640.1406
5/325/320.1563
11/6411/640.1719
3/163/160.1875
13/6413/640.2031
7/327/320.2188
15/6415/640.2344
1/41/40.2500
17/6417/640.2656
9/329/320.2813
19/6419/640.2969
5/165/160.3125
21/6421/640.3281
11/3211/320.3438
23/6423/640.3594
3/83/80.3750
25/6425/640.3906
13/3213/320.4063
27/6427/640.4219
7/167/160.4375
29/6429/640.4531
15/3215/320.4688
31/6431/640.4844
1/21/20.5000

3.Tap Sizes (Metric)

Here are common tap sizes in metric measurements:

Tap Size (mm)Pitch (mm)
M1.60.35
M20.4
M2.50.45
M30.5
M3.50.6
M40.7
M50.8
M61.0
M81.25
M101.5
M121.75
M142.0
M162.0
M182.5
M202.5
M222.5
M243.0
M273.0
M303.5
M333.5
M364.0
M394.0
M424.5
M454.5
M485.0
These are just a few examples of commonly used metric tap sizes. There are many more sizes available depending on the specific requirements of your project.

4.Tap Sizes (English)

Tap Size (inch)Threads per Inch (TPI)
#0-8080
#1-6464
#2-5656
#3-4848
#4-4040
#5-4040
#6-3232
#8-3232
#10-2424
#10-3232
1/4-2020
5/16-1818
3/8-1616
7/16-1414
1/2-1313
9/16-1212
5/8-1111
3/4-1010
7/8-99
1-88
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