What Size Drill Bit for 1/4 20 Tap? A Comprehensive Guide

Determining the appropriate tool size for drilling is crucial for effective construction or repair work. Therefore, understanding what size of drill bit should be used for a 1/4″ 20 tap is a question that often concerns individuals working with these tools. This post is dedicated to offering insights into this aspect, along with essential techniques for dealing with different materials.

Drill Bit Size for a 1/4″ 20 Tap

In the world of construction, details matter. But you can rest at ease when it comes to selecting the appropriate drill bit size for a 1/4″ 20 tap because a #7 drill bit with a diameter of 13/64″ (0.203″) is the best choice. However, a few key considerations are worth heeding before you begin your drilling venture.

It’s crucial to know that if the hole is too small, the bolt may protrude from the center and if the hole is too large, the bolt threads may not connect efficiently with the drilled hole. Another vital factor that may influence the recommended tap drill size relates to the hardness of the material you’re drilling into. Different materials exhibit varying levels of hardness that affect how they interact with certain tools.

Here’s a table showcasing the appropriate drill bit sizes for a 1/4″ screw with different threads per inch:

Screw SizeThreads Per InchDrill Bit Size (75% Thread)Drill Bit Size (50% Thread)

Material Considerations When Drilling a 1/4″ 20 Tap

Various materials necessitate slightly different approaches to drilling. For example, hard materials such as steel, stainless steel, and iron usually demand finer threading at approximately 50%. Under these particular circumstances, the suitable drill bit would be 7/32″ for a 1/4″ 20 tap.

In contrast, softer materials like aluminum, plastic, and brass require a different approach. Always remember to refer to the manufacturer’s instructions to ensure you’re using the correct size tap drill.

How to Drill

Once the drill bit size is decided, the drilling process can commence. When it comes to drilling into metal, it’s important to secure the metal with at least two clamps to avoid any potential injuries caused by spinning metal.

Safety should be a priority whenever you drill. It’s recommended to wear safety eyewear and heavy-duty work gloves to protect your eyes and hands from sharp material remnants.

Marking the location for drilling is the first practical action. You can use masking or painters tape to assist in maintaining the step drill bit’s position, which provides a visual aid and ensures precision.

A step drill bit is an essential tool in any craftsman’s arsenal as it’s designed to start with a small hole and then expand into a bigger one. Effectively utilizing a step drill bit becomes increasingly pivotal when cutting into different types of metal and tougher woods.

How to Use 1/4″ 20 Taps

The purpose of tapping is to create a threaded hole where the screw can securely fit in. The primordial step after drilling the initial hole is to deburr its edge and eliminate any sharp edges. This step protects the integrity of your work while also ensuring safety.

Subsequent to this, a chamfering process will facilitate the tapping process. After thorough cleaning of any debris or dust accumulated in or around the hole, you can set up the tap for the next step.

Pecking: A Tip for Successful Tapping

When tapping threads into a hole, the bottom line is to be patient. It’s recommended that you employ a technique involving alternate forward and backward movement. This method safeguards your tap or drill bit from beginning or breakdown, especially when dealing with hard materials needing high torque for penetration.

In this method, often termed as “pecking,” you turn a full turn of the tap in and then a half-turn out. This tap-dance performs a brilliant job of making the most consistent thread tapping.


This guide has provided you with a comprehensive understanding of what size of drill bit should be used for a 1/4″ 20 tap, how to consider the material, how to handle the drilling process, and how to successfully tap threads into your hole. Always remember that safety comes first, and don’t shy away from seeking advice or help when required.

By following these guidelines, your construction or repair project involving a 1/4″ 20 tap will likely turn out to be a huge success. Whether you’re a novice in DIY projects or a seasoned professional, we hope this information has been valuable to you. Stay tuned for more such comprehensive guides to assist you in all your future projects.

Leave a Comment