two threaded drill bits

Drill Bit Size Guide: What Size Do You Need for a 5/16 Tap?

If you’re planning your next do-it-yourself project for your home, you may need some power tools you haven’t considered using before. Once you’ve got your list prepared of all you’ll need to complete your project, like the right wood sizes, paint, and screws, you’ll need to consider what kind of power tool you’ll need to get the job done.

Often, when drilling holes for a project, you’ll have to match a tap and drill bit to the desired hole diameter. For those who may not know the basics, we’ll walk you through what tap and drill bit size you’ll need for your drilling tool and other important things to remember when choosing the correct size.

Understanding Tap and Drill Bit Sizes

Knowing the correct drill bit size before drilling is vital to ensure you have prepared your surface material for drilling. The tap and drill bit sizes need to match to have your equipment working accurately.

Using a drill bit and tap may be straightforward enough, but following the correct instructions and safety tips will help you achieve accurate results. Using the right drill bit size is simple once you have the right information at hand.

Make sure you know how big you need to make your drill holes and measure the hole’s diameter. You must drill these holes before tapping threads into your working surface.

The two main variables you’ll need to determine the drill tap size are the thread size and pitch. From there, you can determine the size of the drill tap. Having the correct thread size and pitch will ensure the threads are correctly formed, and you can tap into the drill hole.

Here are the different measurements you’ll need for determining the correct two sizings:

  • Tap diameter
  • Full thread percentage
  • Thread pitch
  • Size of the drilled hole

It’s best to measure drill tap size with a tap drill calculator or a chart since there are quite a few numerals to consider.

Tap and Drill Bit Size Conversion Chart
three M14 metal taps

To accurately determine what drill bit size and tap size you need, use a conversion chart to get the appropriate size. These are readily available on the internet, such as this one from the University of Florida’s Department of Mechanical & Aerospace Engineering. This chart lists every screw size in both standard and metric formats.

This calculator from Newman Tools also provides a detailed list to help you determine the correct drill bit size from there.

What Drill Bit Size Do You Need for a 5/16 Tap?

For a 5/16” tap, the drill bit size can vary. It is generally recommended you use drill bit size F for a 5/16 tap; however, this can vary based on the hole diameter you want to achieve. For a 0.2570” hole diameter, use an F-size drill bit.

A 5/16-18 tap works great for metal and plastic materials, and its steel composition makes it efficient, durable, and able to withstand high speeds. They’re easy to install and operate and are typically used for creating threads for the workspace you’re drilling.

Best Practices for Tapping

tapping hole with lubricated metal hand tap

To properly tap your drilling hole, following these best practices is essential. Familiarize yourself with the process of drilling and tapping before getting started.

Drilling is one of the most crucial steps in running your project. Prepping your working area by drilling and following correct procedures will ensure that the rest of your job runs smoothly.

First, prep the surface area and your tools before tapping.

Follow the correct techniques for tapping so that your result is accurate and doesn’t damage the material. Apply just enough force on the drilling tool so that the tap can make a pilot drill hole.

But do not use aggressive force and high speeds, as this can quickly damage and split the wood or metal you’re working on. Change the drill speed depending on the material; for instance, drilling through stainless steel will require a higher speed than drilling through wood.

Avoid common mistakes like incorrectly drilling the hole with the wrong size and using the wrong drill bit. Hold the drill straight and avoid slanting so you don’t create a bigger hole than you need.

Make sure to secure the tap to the drill so objects are not damaged in your work area. Additionally, ensure your workstation is clear, electrical wiring is out of the way, and your working material is properly secured on your workbench.


How do I determine the correct size drill bit for my tap?

To determine the correct size drill bit for your tap, use some simple math to calculate the tap-drill diameters:  Nominal diameter - Thread pitch = Tap-drill diameter.

Can I use a larger drill bit than the recommended size?

While you can use a smaller drill bit than the recommended size, you shouldn’t use a larger drill bit than the recommended size. The larger drill bit simply won’t fit into the screw’s central core diameter.

What happens if I use a smaller drill bit than the recommended size?

Using a smaller drill bit than the recommended size is fine, but small holes may cause the material being drilled to split or crack. A smaller hole could allow the screw to securely and stably hold your object, but it can cause more damage to the material.

Can I use a different type of drill bit than the recommended one?

To drill accurately with a tap, it is best to use the recommended drill bit. Using a different drill bit than the recommended one will result in compatibility issues, as the shank size and diameter must match the tap. The appropriate drill bit should be utilized to ensure an accurate drilling hole.

How often should I sharpen my tap?

There’s no set time to sharpen your tap, as it depends on use. It’s best to sharpen your tap whenever its edges become dull and weathered. If you can no longer sharpen them, then they may need replacing.

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