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1/8 NPT Drill Size: Mastering The Basics

Hey there! You’re not alone if you’ve ever wondered which drill size to use for a 1/8 NPT (National Pipe Thread). Trust me, it can be a head-scratcher. But fear not!

For a 1/8 NPT drill size, pick a tap drill size that fits the thread to drill for a 1/8 NPT. Assuming it’s not curved, choose an 11/32mm drill bit instead of a 21/64mm bit. Super easy!

In this blog, I will explain everything you need about the 1 8 NPT drill size.

There is no fancy jargon, just plain and simple information to help you confidently tackle your drilling projects. So grab your favourite beverage, sit back, and let’s dive in.

What does NPT stand for?

Picture yourself in a world where pipes can talk to each other in their own way. In the US, they use a unique language called National Pipe Thread, which is often just called “NPT.”

And that’s what we mean when we talk about NPT: the special threading style that pipes use to connect and fit together tightly.

It works like a secret code to make sure pipes can talk to each other and join together perfectly. This is why it’s the standard for pipes and fittings all over the country.

So, the next time you see NPT, know that it’s the secret handshake that keeps our pipes talking.

Understanding The 1/8 NPT Drill Size

Understanding The 1/8 NPT Drill Size

So, what’s the deal with the 1/8 NPT tap drill size? Well, it’s the magic number you need to create threads on an internal pipe.

Imagine: You’re getting your pipes ready for a threading party! NPT stands for National Pipe Thread, the go-to threading style in the good ol’ United States.

The 1/8 NPT size is like the smaller sibling of the standard NPT size, perfect for pipes that handle fluids under high pressure.

Picking The Right Tap Drill Size

Now, here’s where it gets interesting. When choosing a tap drill size, you must consider the material you’re working with and how thick it is.

To compare, choose the right tool for the job. For aluminum and other soft materials, you might need a slightly bigger tap drill size than for steel and other tough materials.

Remember, it’s better to lean towards a larger tap drill size to avoid playing rough and damaging your material.

Related post: What Size Drill Bit For 3/16 Rivet?

For a 1/8 NPT tap, what size drill bit do you need?

what size drill bit do you need?

Let’s talk about drill bits now. Those sharp things that poke holes in things. For a perfect fit, start with the right size drill bit when you tap threads.

Putting on the right shoes goes with your outfit—you wouldn’t go to a nice dinner in flip-flops.

This means that the R-type drill bit works best with a 1/8″ NPT pipe tap. Use a 21/64mm (0.339″”) drill bit if your pipe tap has a curved end.

For the straight guns that don’t taper, get an 11/32mm (0.344″) drill bit.

With 27 threads per inch, these sizes make sure that the link is strong and safe. When you find the last piece of the puzzle, everything fits together perfectly.

Why Size Matters in the Drill-Bit World

Now, you might be wondering why the size of the drill bit matters so much.

Well, think of it this way: using the correct drill bit size ensures that your threads fit snugly, like a handshake between two friends.

It’s too big, like trying to high-five a basketball player with tiny hands—inconvenient and ineffective.

Too small, and you’re left with a loosey-goosey connection that’s just waiting to let you down.

The Lowdown on 1/8 NPT Tap Drill Size

Lowdown on 1/8 NPT Tap Drill Size

To sum up, the 1/8 NPT tap drill size is the hole diameter you need to drill to install a 1/8 NPT threaded fitting. It’s like creating the perfect opening for your thread to call home.

This size is ideal for light-duty applications—think faucets, valves, or hose nozzles.

No worries if you’re scratching your head about what size you need! Some online calculators can do the brain work for you. Easy peasy!


There you have it, my friend! We’ve demystified the 1/8 NPT tap drill size together.

Now, armed with the knowledge of the correct drill size, you’re ready to tackle your next drilling project like a pro.

No more second-guessing, just pure confidence in every turn of the drill. Happy drilling!


What size hole should I drill for a 1 8 NPT tap?

For a 1/8 NPT tap, drill a hole with a 21/64mm bit if it’s tapered, and an 11/32mm bit for non-tapered.

What is 1/8 NPT thread size?

The 1/8 NPT thread size is a standard for pipes in the United States, used for tapping threads on internal pipes.

What is the drill bit for 1/8 thread?

The recommended drill bit for a 1/8 NPT thread is 21/64mm for tapered taps and 11/32mm for non-tapered taps.

How do I determine the right tap drill size for my material?

Consider the material’s hardness; for softer materials like aluminum, choose a larger tap drill size than you would for harder materials like steel.

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