What is 1/8 Pipe Tap Drill Size


If you’re a handyman or woman, you likely know the importance of having the right drill bit for the job. But what about taps? Do you know what size tap to use for a 1/8″ pipe? If not, don’t worry – we’re here to help. In this blog post, we’ll tell you everything you need to know about 1/8 pipe tap drill size. Whether you’re a beginner or an experienced pro, this is information that will come in handy next time you need to do some work on pipes. So let’s get started.

What is 1/8 Pipe Tap Drill Size?

The 1/8 pipe tap drill size is a measure of the diameter [1] of the hole that needs to be tapped for a 1/8-inch pipe tap. This size is also known as the NPT (National Pipe Thread) size. The NPT size is used for both American and Metric Pipe taps. The number after the dash in the NPT size ( such as 1/8-18 NPT) indicates the number of threads per inch that need to be cut into the hole. 

1-8 pipe hole

In this case, it would be 18 threads per inch. To find the right drill bit size, simply measure the diameter of the hole that needs to be tapped and subtract the thread pitch from that measurement. 

What Size Drill Bit Do You Use for a 1/8-inch Tap?

When choosing a drill bit for a 1/8-inch tap, it is important to select a bit that is the same size or slightly larger than the tap. This will ensure that the hole is the correct size and that the threads will properly engage with the workpiece. For most applications, the “R” drill bit will be sufficient. However, if the material is particularly hard or the hole needs to be very precise, it may be necessary to use a larger bit. 

In general, it is always better to err on the side of a larger hole, as this can be corrected by using a smaller tap. As long as the hole is not too large, the tap should easily create the correct thread size.


The 1/8 pipe tap drill size is the most common size for taps. It can be used on a wide variety of materials, including steel, brass, aluminum, and plastic. The 1/8 pipe tap drill size is perfect for creating threads in pipes that have an outside diameter of 1/2 inch or less.

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