1/2-28 Tap Drill Size — Your Quick Guide

1-8 NPT port

A 1/2 28-tap drill size is a drill bit size used to create a threaded hole in a workpiece. It is a standard-size tap drill used in the United States. The 1/2 28-tap drill size has a diameter of 0.500 inches and 28 threads per inch (TPI).

Understanding the Different Sizes of Tap Drills

Tap drills are available in a variety of sizes, depending on the type of material and thread you need to create. The most common sizes for American Standard Threads (UNC/UNF) are:

Tap Drill Sizes

#4 – 40

#6 – 32

#8 – 32

#10 – 24

#1/4 – 20

#5/16 – 18

#3/8 – 16

#7/16 – 14

#1/2 – 13

#9/16 – 12

#5/8 – 11

#3/4 – 10

#7/8 – 9

#1 – 8

#1 1/8 – 7

#1 1/4 – 7

1/2 – 28

Using the Right Tap Drill Size

When selecting a tap drill size, it is important to choose the size that is most appropriate for the material and thread you are trying to create. For example, a tap drill size of 1/2-28 would be used to create a 1/2-inch thread in a metal workpiece.

The same size tap drill could not be used for a 1/4 inch thread, as it would not create the correct thread pitch.

What Size of Drill Bit is Used for a 1/2-28 Tap?

When drilling a hole for a 1/2 28 tap, it is important to use the correct size drill bit. The correct size drill bit for a 1/2 28 tap is typically a #7 drill bit, which has a diameter of 0.201 inches.

Drill bits also vary by angle to choose the best for ones use

It is important to use the correct size drill bit in order to create the correct thread pitch and to avoid any issues with the tap not seating correctly in the hole.


For making threaded holes in workpieces, the common size in the US is a 1/2 28-tap drill. It has a 0.500-inch diameter and 28 threads per inch (TPI).

It’s crucial to select the tap drill size that is best for the material and thread you want to make while making this decision. A metal workpiece is commonly threaded to 1/2 inch using a 1/2 28-tap drill size.

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