A drill and tap chart is what specifies the right size of drill bit that one can use to create the correct sized opening that would complement tap dimensions. A tap drill chart is key in matching pairs of female and male thread that tightly secure together. Often it is the corresponding dies and taps that you see together when buying either ones. However, the particular drill chart is essential for sizes of the drills only.

Tap is required to make female screw threads. The die is required to make a male screw thread and has a tiny split on its side that allows for adjustment of the screw, it also allows it to be a bit altered for different degrees of sharpness and different materials.

Tap Drill Chart

How to Convert Drill Bit Sizes

The first thing you do is consult the tap drill chart to look for the accompanying drill bit size for a tap, most of these are available online. There are tap drill charts, which will give you the right tap for drilling in both measurements of millimeters and inches. You will need taps for manufacturing of parts, where a hole is required to be made with a female screw thread when building and fastening. It is true that there are tons of different ways you can make this hole but using a tap to thread the hole is the most common one.

All standard size taps come with at least one drill bit size that corresponds to it. These are a bit bigger than the skinniest area of the male screw, but at the same time also smaller than the thickest area of that screw. When you want to find the right sized drill and tap size, you also need to know if the screws that you will be using are fine or coarse. This helps with thread spacing, which is important in determining the right drill bit size. This is also because then the tap is able to make varying depths between 50 percent and 100 percent, depending entirely on how big a hole is.

Drill Size Chart

How Can One Use the Drill Chart

Expert installers and manufacturers make use of the drill and tap chart to determine what taps and drills sizes to pick out for a combination that results in female screw guides. This is what allows workers and homeowners to in time add the components that would complete predrilled items. Drill and tap charts rely on comparing the size of a drill bit in the chart, to figure out what drill bit makes the right sized hole. After this, manufacturers then drill the hole of the right length, put the tap, and start making the guides. When they twist the taps it carves out guides of the right size. It also ensures a snug fit for treads of screws. Drill charts work nicely with wood and metal components. The guides are built via the correct use of taps and charts for wood screws and machine screws.

If you are going through these charts you will also find Imperial Charts which allow users to compare diameters in inches instead of in millimeters. It fulfills the same purpose, but is essential if you are faced with guides that cover over an inch sized drill bits. Remember depth varies from chart to chart which means metalworkers should know what depth they need so that they only use one chart for making guides.  Here is a simple way you can use them.

Create a fresh thread inside a hole by first re-drilling the existing hole. Look to the tap and drill chart for the correct size and start drilling. Next, position the square of the tap on top of the holder and tighten it. After that place the tip of tap inside the hole, make sure the tap is positioned in a perpendicular direction to the hole. You have to then press down and turn the tap inside the hole. The tap then cuts the thread in the wall of hole. When you have made at least 2 full turns, turn the tap backwards around half or three-fourth of a turn, you might even need 3 instead of 2 turns at first. This helps in loosening the chip.

If you are working with dies you should know that they are used the same way. The only difference is that they are applied on a round rod and not a drilled hole. The size of the die that you pick out has to be the same size as the rod. For instance if you want a rod that is 3/8”, your die has to be of the same size.

Drill Bit Sizes


How to Read a Tap Drill Chart

The tap and die chart corresponds to different drill sizes and diameters. All you have to do to read it is to match the size of drill with the right characteristics like the thread count for every inch and the material type of a drill. Taps cut internal threads to suit different applications.  They are available in the most common 4 types:

  1. Taper tap
  2. Bottoming tap
  3. Plug taps
  4. Machine screw taps

Taper taps are used to cut threads that travel through a hole. Plug taps work on threads that only halfway go through a hole.  Machine screw taps are the smallest you will find and are meant for small diameter holes. You can easily find the size of a hole that you have to drill, by going through the chart. Bottoming taps come in handy when you need threads to go through entirely to the bottom.

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TemplateLab April 29th, 2021