What is 1/4 28 Tap Drill Size


Have you ever wondered what the tap drill size is for a 1/4-28 tap? If so, you’re not alone. In this blog post, we’ll answer that question. Read on to learn more.

What is 1/4 28 Tap Drill Size?

1/4 28 is a tap drill size for creating threads in steel, brass, and bronze. The “1/4” refers to the diameter of the drill bit, and the “28” indicates that 28 threads per inch will be produced. This particular tap drill size is most commonly used for creating threads in pipes and fittings. 

1.4 28 tap drill

When using a 1/4 28 tap drill, it is important to use a lubricant such as cutting oil to prevent the tap from overheating. If the tap becomes too hot, it can damage the workpiece or break the tap. 

What Size Drill Bit Do You Use for a 1/4-28 Tap?

When it comes to tapping holes, the size of the drill bit is just as important as the size of the tap. If the drill bit is too small, it will cause the tap to break or become stuck. If the drill bit is too large, however, it will damage the threads and make it difficult to create a tight seal. For a 1/4-28 tap, the ideal drill bit is the number 3. This will create a hole that is just slightly larger than the tap, making it easier to start the thread without stripping it. 

In addition, using a slightly larger drill bit can help to prevent breaking taps, which can happen when the hole is too small and the tap becomes stuck. With a little care and attention to detail, you can ensure that your project turns out just the way you intended.

How Do You Choose a Drill for a Tap?

When choosing a drill for a tap, the first thing you need to consider is the size of the tap. The tap size will determine the major diameter of the screw, which in turn will dictate the best tap drill size. Generally speaking, a good tap drill is 90% (± 2 pp) of major diameter for fine threads. For metric V threads, the concept of major minus pitch (i.e. the major or widest diameter of the screw in millimeters [1] minus the pitch of the threads of that screw in millimeters per thread) yields a good tap drill diameter. 


Once you know the size of the tap and drill you need, you can then select the specific type of drill based on the material you’ll be drilling into and the finish you’re looking for. With this information in hand, choosing the right drill for your next tapping project should be a breeze.


The 1/4 28 tap drill size is a term that is used in the manufacturing and machining industry. It refers to the size of the drill bit that is used to create a 1/4-inch hole. A 1/4 28 tap drill size is one of the most common sizes that are used in production, and it can be found in a variety of different applications.

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