Drill Bit Sizes For Tapping

One of the most common problems that faced in my early days of DIYing, I really had some trouble with the messy tap and drill bit size chart that I hung on my wall. Those messy numbers and inches figure wasn’t simply easy to understand.

While I got to work with drills of 1/8”, 1/32” or so, I used to have hard time. Often, I misled myself towards wrong sizes of drill bits, and eventually wrong size of wholes.

But in this article, I have to put something that helps you to avoid such mistakes. You’ll find a complete size chart for drill tap and sizes.

What is A Trap Drill for Any Size of Thread?

First thing first, let’s discuss who do handymen and DIYers have to be so precise with the drill bit sizing charts for different sizes.

When you deal with a manufacturing, there must be a female screw thread that needed to be complemented by screws. To make the joint stronger and fastener, one drills a hole first and then tap the hole with a tap.

On that purpose, each of these female screw threads has its size of drill bits that will work on it. And that where workers have to be pitch and diameters.

The Drill and Tap Size Chart

Before talking about the drill size for some common uses, let’s have a look at the complete sizing chart first-


Size of the Tapping
Threads
per inch
Drill size w/ taper
pipe reamer
Drill size w/out
taper pipe reamer
Straight pipe
threads
1/162715/64D1/4
1/82721/64Q11/32
1/41827/647/1629/64
3/8189/1637/6437/64
1/21411/1623/3223/32
3/41457/6459/6415/16
111.51 1/81 5/321 11/64
1 1/411.51 15/321 1/21 33/64
1 1/211.51 23/321 47/641 3/4
211.52 3/162 7/322 7/32

The Rules of Thumb for the Drill Bit Size for Tapings

To go smooth with the chart, here are some rules of thumbs-

  • An ideal tap drill should be of 85% of the major diameter of the coarse thread you are working on.
  • For the fine threads, the size of a tap drill would be 90% of the major diameter.
  • If you’re working with the Metric Drill Bit size standards, then you may go through the Major Minus Pitch that decides the drill bit sizes for any tapings.
Charles Thompson
 

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