Tap Drill Charts: A Comprehensive Guide For Every Machinist

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23 Printable Tap Drill Charts [PDF] Template Lab
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Tap drill charts are an essential tool for machinists and anyone involved in metalworking. These charts provide valuable information about the size of the hole that needs to be drilled before tapping threads into it. In this article, we will explore the importance of tap drill charts, how to read and use them, and provide some helpful tips and tricks. Whether you are a beginner or an experienced machinist, this guide will help you understand and utilize tap drill charts effectively.

Why are Tap Drill Charts Important?

Tap drill charts serve as a guide to determine the appropriate hole size for threaded holes. They provide information about the diameter and depth of the hole, ensuring that the threads will fit securely and function properly. Using the wrong tap drill size can result in stripped threads, weakened connections, and overall poor performance. By referencing tap drill charts, machinists can avoid these issues and achieve accurate and reliable results.

How to Read a Tap Drill Chart

Tap drill charts typically consist of two columns: one for the size of the tap and another for the corresponding drill size. The drill size is listed in fractions, decimals, or metric measurements, depending on the chart. To determine the correct drill size, locate the tap size in the chart and find the corresponding drill size. For example, if you are using a ¼-20 tap, you would find ¼-20 in the tap size column and look across to find the recommended drill size.

Tips for Using Tap Drill Charts

1. Use the correct type of tap drill chart for your project. There are different charts for metric, fractional, and numbered tap sizes.

2. Always double-check the tap size and corresponding drill size before drilling. Mistakes can lead to costly errors.

3. Consider the material you are working with when selecting the drill size. Softer materials may require a slightly larger hole to accommodate the threads.

4. If you are unsure about the appropriate drill size, consult a tap drill chart or seek advice from experienced machinists.

5. Keep your tap drill charts organized and easily accessible. Having them readily available will save time and prevent mistakes.

Sample Tap Drill Charts

Here are five sample tap drill charts for different thread sizes:

1. Metric Tap Drill Chart

Tap Size (mm) – Recommended Drill Size (mm)

M2 – 1.6

M3 – 2.5

M4 – 3.3

M5 – 4.2

M6 – 5.0

M8 – 6.8

M10 – 8.5

M12 – 10.2

2. Fractional Tap Drill Chart

Tap Size (inches) – Recommended Drill Size (inches)

1/4-20 – 7/32

5/16-18 – 17/64

3/8-16 – 5/16

1/2-13 – 27/64

5/8-11 – 17/32

3/4-10 – 21/32

1-8 – 55/64

3. Numbered Tap Drill Chart

Tap Size (number) – Recommended Drill Size (inches)

No. 4-40 – #43

No. 6-32 – #36

No. 8-32 – #29

No. 10-24 – #25

No. 12-24 – #16

No. 1/4-20 – F

No. 5/16-18 – U

4. Pipe Tap Drill Chart

Tap Size (NPT) – Recommended Drill Size (inches)

1/8-27 – 11/32

1/4-18 – 7/16

3/8-18 – 37/64

1/2-14 – 23/32

3/4-14 – 59/64

1-11.5 – 1-5/32

1-1/4-11.5 – 1-1/2

5. STI Tap Drill Chart

Tap Size (UNC) – Recommended Drill Size (inches)

2-56 – #56

4-40 – #43

6-32 – #36

8-32 – #29

10-24 – #25

1/4-20 – F

5/16-18 – U

Frequently Asked Questions (FAQs)

1. What is a tap drill chart?

2. Why do I need a tap drill chart?

3. How do I read a tap drill chart?

4. Are tap drill charts different for metric and fractional sizes?

5. Can I use a larger drill size than recommended in the tap drill chart?

6. Where can I find tap drill charts?

7. Are tap drill charts the same for all materials?

8. What happens if I use the wrong tap drill size?

9. Can I create my own tap drill chart?

10. How often should I refer to tap drill charts?


tap drill charts, machinists, metalworking, threaded holes, tap size, drill size, metric, fractional, numbered, pipe tap, STI tap, FAQ, thread sizes, hole size, accuracy, reliability, tips and tricks

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