Tap Drill Chart: Everything You Need To Know

Tap Drill Chart Business Mentor
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When it comes to working with metal, having the right tools and knowledge is essential. One tool that is often overlooked but plays a crucial role in metalworking is the tap drill chart. Whether you are a professional machinist or a DIY enthusiast, understanding and using a tap drill chart can greatly improve your efficiency and accuracy. In this article, we will explore what a tap drill chart is, how to read it, and why it is important. So, let's get started!

What is a Tap Drill Chart?

A tap drill chart is a reference tool used in metalworking to determine the appropriate drill bit size for creating threaded holes. It provides a comprehensive list of drill bit sizes and their corresponding thread sizes for various types of taps. By using a tap drill chart, you can ensure that the hole you drill is the correct size to accommodate the tap and produce properly threaded holes.

How to Read a Tap Drill Chart

Reading a tap drill chart may seem daunting at first, but with a little practice, it becomes a valuable skill. Here's a step-by-step guide on how to read a tap drill chart:

Step 1: Identify the Thread Size

The first step in reading a tap drill chart is identifying the thread size you need. This is usually specified in the project's blueprint or can be measured using a thread gauge. The thread size is typically indicated by the number of threads per inch (TPI) or by a metric measurement.

Step 2: Locate the Thread Size on the Chart

Once you know the thread size, find it on the tap drill chart. The chart will have columns for different thread sizes, usually organized by TPI or metric measurements. Locate the column that corresponds to your thread size.

Step 3: Identify the Tap Drill Size

After finding the correct column, look for the row that corresponds to the type of tap you are using. The chart will provide the recommended drill bit size for that particular tap size and thread pitch. This is the size of the hole you need to drill before tapping.

Why is a Tap Drill Chart Important?

A tap drill chart is important for several reasons:

Accuracy: Using the correct tap drill size ensures that the threaded hole you create will be accurate and fit the intended fastener perfectly.

Thread Strength: Using the proper tap drill size helps maintain the strength of the threads. If the hole is too small, the threads may strip or tear. If the hole is too large, the threads may become weak and prone to stripping.

Efficiency: By using a tap drill chart, you can quickly determine the correct drill bit size without trial and error. This saves time and reduces the risk of errors.

Consistency: Using a tap drill chart ensures consistency in hole sizes across different projects. This is especially important if you are working on multiple parts that need to fit together seamlessly.

Sample Tap Drill Chart

Here is a sample tap drill chart for reference:

Sample Tap Drill Chart

Frequently Asked Questions (FAQ) about Tap Drill Charts

Q: Can I use a drill bit that is slightly larger or smaller than the recommended tap drill size?

A: It is generally not recommended to use a drill bit that is significantly larger or smaller than the recommended tap drill size. This can affect the accuracy and strength of the threads.

Q: Can I use a tap drill chart for different materials?

A: Yes, a tap drill chart can be used for different materials. However, it is important to consider the specific properties of the material you are working with. Some materials may require different tap drill sizes for optimal results.

Q: Where can I find a tap drill chart?

A: Tap drill charts are readily available online, in machining handbooks, and in metalworking reference books. You can also create your own tap drill chart based on your specific needs.

Q: Can I use a tap drill chart for metric threads?

A: Yes, tap drill charts are available for both imperial (inch-based) and metric threads. Make sure to use the correct chart for the thread system you are working with.

Q: Are there any alternatives to using a tap drill chart?

A: While a tap drill chart is the most reliable and accurate method for determining the correct drill bit size, there are alternative methods such as using thread gauges or trial and error. However, these methods may not guarantee the same level of accuracy and efficiency as using a tap drill chart.


A tap drill chart is an indispensable tool for anyone working with metal and creating threaded holes. By understanding how to read a tap drill chart and using it correctly, you can ensure accuracy, strength, and efficiency in your metalworking projects. So, next time you reach for your drill and tap, don't forget to consult the tap drill chart!


tap drill chart, metalworking, thread size, drill bit size, thread gauge, accuracy, thread strength, efficiency, consistency, materials, metric threads