3/8″ Tap Drill Size

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It’s not always easy to find out what drill bit you require. And at most times, it can get frustrating, especially if you’ve ruined a project just because of the wrong size drill bit. 

However, if you want to know the best drill bit for a 3/8 tap drill size, you’ve come to the right place.

What are the Drill Bit Sizes for a 3/8" Tap?

A 37/64″ drill bit is needed for a 3/8″ NPT tap.

NPT Tap SizeDrill Bit Size

How Tap Sizing Works for 3/8"

To fit the drill bits (shown in our chart), which are six inches long, you specifically need a 3/8″ NPT Tap and Drill.

You also have to remember that 3/8″-16 Tap and 3/8″-24 are not the same thread pitches.

You can utilize e 3/8″ NPT tap in various DIY projects. If you intend to utilize screws or bolts, you can use a 3/8″ NPT tap to drill pilot holes. The material you use can affect how well you can drill them.

Tap Drill bits

A hammer drill is ideal for drilling into concrete and other hard materials. Cordless or corded drills can be used if you’re working with wood. Consider a corded drill if you need extra power.

You’ll need to be extremely careful when drilling a pilot hole in wood. Don’t split the wood while you’re at it! You’ll need a pilot hole to fasten two pieces of hardwood together.

Calculating the Tap Drill Size for 3/8"

The first step is to determine the size of your drill bit. It’s a straightforward procedure that does involve some mental math. Take the tap’s diameter [1] into consideration.

When determining a thread pitch to utilize, you need to consider the diameter of the drill. It doesn’t matter which one you choose, but you should choose the one that best matches your desired outcome.

Compared to a 24-inch tap, a 16-inch tap cannot generate as many threads. For the second time, you’ll want to pick a size that’s most comfortable for you. The drill bits you’ll need will depend on whether you’re using either.

tapping hole

When utilizing a 3/8″-16 tap, you need at least a 5/16″ drill bit. For a 3/8″-24 tap, a Letter Q or 21/64-inch drill bit is required.

Regardless of the taps and thread pitches, there is little difference in diameter. When drilling bit sizes, the smallest distinctions can make a big difference.

Why Do 16" And 24" Taps Require Different Sizing?

With so many options, knowing which is best for your application. They are still both sized the same way.

When comparing the two, pay attention to their thread counts.

Your project will suffer if you use a drill bit that doesn’t fit correctly. Use our chart to determine which 3/8″-16 or 3/8″-24 you should use or prefer. If you need a complete size chart of tap drills, you can check this guide.

Drill Bit Size for 8-32 Taps

Use some scrap material to test if 3/8″-16 or 3/8″-24 works for your project. Preparation is preferable to winging it when it comes to a project.

It all boils down to the type of drill bit you desire. You must consider even the smallest details to get the intended outcome. You may want to drill holes and test before you get started on your project.

You can experiment by switching out the appropriate drill bits to determine which holes produce the required results. Your actual work can begin after deciding what you need between 3/8″-16 and 3/8″-24.


For a 3/8″ tap drill size, various drill bits are compatible. You can narrow down your options by determining the ideal thread length. Because they work well with various materials, pair the appropriate drill bits with instruments you will need.

Robert Johnson is a woodworker who takes joy in sharing his passion for creating to the rest of the world. His brainchild, Sawinery, allowed him to do so as well as connect with other craftsmen. He has since built an enviable workshop for himself and an equally impressive online accomplishment: an extensive resource site serving old timers and novices alike.
Robert Johnson
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