What Size Drill Bit for 1/4” NPT Tap?

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The ¼” NPT tap is a small pipe tap used for cutting internal threads in pipes. ¼” NPT taps are generally made of steel and are usually heavier than most taps If you want to know what size drill bit for a ¼” NPT tap is, read further.

What Size Drill Bit for 1/4” NPT Tap?

A  ¼” NPT Tap needs a drill bit size of 7/16 inches or 0.4375 inches in decimals. NPT taps are commonly called pipe taps by most people. Don’t confuse them with NPTF taps and tapered taps like the 8-32 tap as they are used for different purposes.

Various kinds of drill bits and screws in an opened blue container

The ¼ NPT tap is commonly used for tapping pipe fittings and couplings much like the 1/8″ NPT tap. It can be used in a wide variety of materials.  You also have to apply a sealer for the NPT threads to work.

To check if you’re actually using a ¼” NPT tap, you can refer to the following specifications (for high-speed steel pipe tap only):

  • Tool Type: Taper
  • Thread Diameter Size: ¼ inch
  • Threads per Inch: 18
  • Thread Standard: NPT
  • Flute Count: 4
  • Overall Length: 2 – 7/16 inches
  • Thread Cutting Part Length: 1 – 1/16 inches
  • Chamfer: 2.5P
  • Coating: Bright
  • Cutting Edge Material: HSS
  • Measurement Type: Pipe
  • Series/List #: 2119
  • Thread Size: ¼” – 18

Tips for Using Medium Drill Bits

Deburr the Hole

Most medium drill bits are used for drilling holes. So, deburring the hole is a sensible thing to do. After you’re done drilling, make sure the hole does not have sharp edges or burr left in the hole. Feel the hole until it’s smooth.

It ensures your hole is smooth and clean, so you produce quality work. You can deburr a hole by running it in a bit of power and running the bit around the edges of the hole.

You can also use deburring tools to make the process simpler and easier. Most of them come with an instructional, so you should have no problems learning to properly use them.

Man using a drill to fasten screws for a white window

Know Your Drill Speed

For medium drill bits, it’s important to know the speed of the drill. Drill bits get hotter the faster it spins. When drilling metal or bricks, most people would set their drills to low speed and pressure. This is to avoid overheating and damage to the drill.

The drill’s speed should be adequate for the size of the drill bits, which is medium. The bigger your drill bits are, the slower the speed should be. For medium drill bits, moderate speed is generally what you want. It helps you drill through metal and bricks faster and with better precision.

Maintaining the right speed helps prevent the drill from overheating. If you see smoke coming from your drill, it’s a sign that you should stop what you’re doing and let your drill cool down.

Consider Using Stud Finder

A stud finder ensures you are not drilling into a water pipe or electric cables. Drilling through electric cables can create a huge accident, like electrocuting yourself. So, it’s best to use a stud finder as a safety precaution.

It’s also useful to avoid hitting water pipes which can cause leakage and flooding in your home. You should use a stud finder when drilling with hazardous materials near the drilling spot.

If you’re drilling into an unfamiliar surface, it’s best to use a stud finder to ensure you are drilling precisely and accurately. It’s better to be safe than sorry.


¼” NPT taps need a 7/16 inches drill bit and can be used to cut internal threads. They’re mostly used for tapping fittings and couplings. They’re also one of the smallest NPT taps you can use.