What Size Drill Bit For 1/4″ 20 Tap (Uses and Functions) Explained

The correct size drill bit for drilling a 1/4″ 20 tap is 5/64.

The most common size of tap is M10x1.5 and the size of the corresponding drill bit is usually given as 5/64. This is because the standard metric thread pitch is one millimeter per thread, so one thousandth of a millimeter is called a thousandth or thou (abbreviated as “T”).

Therefore, the drill diameter should be 0.0564 inches (0.1479 mm) or 0.0937 inches (0.2335 mm). The former number refers to American inch-based units, while the latter refers to British inch-based units (which are slightly different).

The actual sizes used in manufacturing are often slightly different from these values, because they are based on measurement tolerances that are related to the accuracy with which a hole can be drilled by hand; an automated machine might have different tolerances and produce holes that are slightly oversize or undersize for this reason.

What Does a 1/4-20 Tap Mean?

A guy with glasses thinking and wonderingA 1/4-20 tap is a type of threading used on many screws and bolts. This type of thread is used in woodworking, metalworking and construction. The number “1” refers to the diameter of the screw’s shaft, while the number “4” refers to its length.

A tap is a tool used to create threads in metal, plastic or other materials. The tool has a cutting edge which creates threads in the material by cutting away material as it moves through the material.

A 1/4-20 tap has a single flute and cuts threads on one side (single-cut) or both sides (double-cut). A single flute means that there is only one groove cut into the tap; double-fluted taps have two grooves cut into them.

How Do you Drill and Tap a 1/4-20 Hole?

There are a number of ways to do this job.

Use a Power Drill With a Tap Holder Attachment

A tap holder in white backgroundThis is much easier than drilling by hand, but it’s still pretty difficult because you have to hold the tap holder in place while tightening down on the chuck with your hand. You run the risk of breaking off or stripping out your threads when tightening down on the chuck too hard, so use care when doing this step!

Use a Twist Drill Bit

A twist drill bit in white background

In this method, you start with a 1/4-20 drill bit and turn it by hand or with an electric drill until the hole is deep enough to accept the tapped part. You then use pliers to unscrew the tap from its handle and insert it into the hole.

Turning it clockwise will cut threads in the metal while also creating a smooth-sided hole through which you can insert your threaded fastener without having to hammer them in with a hammer.

How Do You Determine the Drill Size for a Tapped Hole?

A circular hole in a wood

To determine the size of a tapped hole, first you need to know the size of the bolt that will be inserted into the tapped hole. The most common metric bolts are M3, M4, M5, M6 and M8. The most common imperial bolts are 10-32, 1/4-20 and 5/16-18.

The easiest way to find out what size drill bit you need is to use a bolt gauge. This tool has multiple holes in it that are sized specifically for each type of bolt.

Simply insert your bolt into the appropriate hole until it fits snugly against the edge. Then look at your drill bit chart to see what size drill you should use for your tapped hole!

Another way is to measure the diameter of your bolt head or nut and compare this measurement with a chart of drill bit diameters available online or from your local hardware store.

Uses of ¼″ 20 Tap

Here are some things you can do with your ¼” tap.

Fix the Pipes in Your Home

A system of metal pipes

If you have pipes that leak, you need to get them fixed. The most reliable way of fixing any pipe is by using a tap. A tap is a tool that allows you to make holes on different materials and then create threads in them. If you want to use this tool for fixing your pipes, then all you need is 1/4″ 20 Tap.

This type of tap is designed specifically for making holes in metal surfaces. It can make holes in any material that has a thickness of up to 3 inches. However, if you want to make holes larger than 3 inches, then it’s better if you use a drill bit instead of the 1/4″ 20 Tap.

Connect Two Pieces of Wood Together

Two pieces of wood connected to each other

If you want to join two pieces of wood together, then all you need is 1/4″ 20 Tap and some screws or nails. The first step involves drilling holes through both pieces of wood using the drill bit attached with the 1/4″ 20 Tap.

Afterward, insert screws or nails into these holes and tighten them until they secure both pieces of wood together tightly enough.

Threading a Hole


A cross-section of a threaded hole


The 1/4″ 20 tap is used to cut threads into a hole. This can be done with a hand drill or power drill. The hole should be drilled first, and then the threads can be cut with the 1/4″ 20 tap. This will ensure that you have a perfect fit.

Drilling Holes in Metal

A hole drilled into metal

You can use this tool to drill holes into metal, but only if it is not too thick and if you have access through one side of the material. You will need a hammer drill for this purpose, as it will make it easier to penetrate through the material.

If you don’t have access from one side and you are drilling through thick metal, it is better to use an impact driver instead of using a hammer drill with this tool attached to it.

Screwing Small Screws Into Wood

Pieces of small screws on wood

The 1/4″ 20 tap can also be used for screwing small screws into wood without having to pre-drill them first (as long as there is room for the head of the screw). Just use some lubricant so that there are no problems with getting stuck or breaking off heads when attempting to turn them after they are all inserted properly into their respective holes.

Final Thoughts

The 1/4-20 tap is a tool used to make holes in metal that are the same size as this type of screw. A drill bit is also needed to make these holes, but you can use either a standard drill bit or a step drill bit.

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