What Size Drill Bit For 1/4″ 20 Tap?

Drill bits are useful equipment that everyone may use, from a DIYer to a professional craftsperson. However, to avoid damaging the material you are drilling into, you must first understand essential information like what size drill bit is required for a standard 1/4″20 tap.

As a driller, you must be familiar with the many kinds and sizes of drill bits, as well as how they differ.

You have to remember that drill bits are not all the same size. They are made in various sizes to serve a particular purpose.

This article covers the complete list of basic drill bits sizes and how to utilize them. Keep reading to discover the best drill bit for your job.

How do Drill Bits work?

Drill bits are an essential component of DIY enthusiasts’ and professionals’ toolsets.

It would not be easy to carry out fundamental building operations without them. Nothing is too large or little for drill bits, from drilling and fastening the frame on a roof to hanging pictures.

The drill’s chuck holds drill bits in position. When you turn on the drill, the chuck spins around, producing torque and the axial speed required to make the hole.

It firmly grips the drill bits, effectively holding them in place until the operator removes them. Drill bits feature a shank on one end that fits into a drill chuck and cutting edges on the other.

The features and components of standard drill bits vary in many ways. They are as follows:

  1. The Spiral: Rate of twist of the drill bit, which determines the pace of chip removal.
  2. The Point Angle: Angle produced at the bit’s cutting point. For various kinds of material, you will need drill bits with varying tip angles.
  3. The Lip Angle: Determines how much assistance the cutting edge of drill bits receives.
  4. The Mechanic: What suppliers frequently use to define the length of drill bits.

How Many Drill Bit Sizes Are There?

If drill bit sizes were based on holes, there would be an unlimited number of bits. However, standard-sized holes and bits are available on the market.

There will only be a few hundred or so appropriate drill bit sizes for each application area. There are sizes for home repair and construction projects, hobbies, maritime, farming, woodworking, metalworking, aviation, arts and crafts, commercial building projects, equipment, and more.

In reality, most high-quality sets contain anything from 12 to 30 standard drill bit sizes. You can see how many sizes there are by looking at our drill chart displayed below.

There are many types of drill bits you can use for a variety of needs. Also, consider what material you are drilling into.

Let’s start with a simple multi-purpose set for the sake of simplicity. Consider a standard 29-piece set.

The drill bit sizes shown in the table below are standard fractional sizes for this kind of set.

1/16″5/32″1/4″11/32″7/16”
5/64″11/64″17/64″23/64″29/64″
3/32″3/16″9/32″3/8″15/32″
7/64″13/64″19/64″25/64″31/64″
1/8″7/32″5/16″27/64″1/2″
9/64″15/64″21/64″13/32″xxx

There are bigger sets available. Specialty fasteners may need a size that is considered uncommon.

Drill bit sizes lower than 1/16′′ and bigger than 1-1/2′′ would be included in bit sets with even more varied drill bit sizes.

Every comparable bit size known to artisans is between these small and large sizes, ensuring that you always have the precise size required depending on what your task requires.

The typical drill bit sizes for spade bits (13-pieces) are as follows: 1/4′′, 3/8′′, 1/2′′, 5/8′′, 11/16′′, 3/4′′, 7/8′′, 9/16′′, 1′′, 1-1/8′′, 1-1/4′′, 1-3/8′′, and 1-1/2′′.

If you require drill bit sizes bigger than 1′′, Spade bits are frequently used for wood and other soft materials.

What Size of Drill Bit is for 1/4″ 20 Tap?

It doesn’t happen very frequently around the home, but you may need to tap new threads into metal from time to time. Before tapping, drill a smaller hole than the tap but big enough to cut the edges.

Tapping threads is a simple idea, but it may get complex in reality.

If the hole is too tiny, the tapping will extend too far into the center, making screwing the bolt into the hole. However, if the drilled hole is too big, the bolt will not match well enough with the threads.

One of the most popular sizes is a quarter-inch with 20 threads per inch. Therefore you should know what size drill bit for 1/4′′ 20 taps to use. To address the question, the overall size drill bit for a 1/4′′ 20 tap is a #7 drill bit with a 13/64″ dimension.

LudoPam 13/64 Inch Cobalt Drill Bit Set, M35 HSS Twist Jobber Length for Hardened Metal, Stainless Steel, Cast Iron, Pack of 10

The typical tap drill is 75% for ordinary or softer materials, but it can be reduced to 50% for tougher materials that need a tighter connection with the screw or bolt.

When tapping tougher materials, the finer threading of 50% may be preferable. This may affect the size of your drill bit, recommending a 7/32″ drill bit for 50 % tap drill for 1/4″ 20 taps.  

Tap and Drill Bit Size Table

Tap and Drill Bit Size Table

A drill size chart and a tap size chart would be required to identify the appropriate tap drill for a particular thread size or the proper tap for an existing hole.

The drill size chart is a table that lists standard-size drill bits in fractional, metric, wire gauge number and letter measurements. Metric sizes are measured in millimeters, while fractional sizes are measured in inches.

Letter and wire gauge systems relate to tool sizes that rise as the wire gauge lowers from #107 to #1 and then from A to Z. The decimal equivalents are given in English and Metric units.

On the other hand, the tap size chart is a table that includes standard size taps for fractional, metric, and screw sizes, giving the diameter and thread spacing.

Fractional sizes are given inches following the letter “M,” whereas metric sizes are indicated in millimeters. A screw size number refers to a diameter that becomes bigger as the screw size increases.

Thread spacing is given after the diameter. Thread count, measured in threads per inch, is used in fractional and screw size systems, such as UNF threads and UNC threads.

The thread pitch, which is the spacing between threads measured in millimeters, is used in the metric system.

How to Use a Drill bit for a 1/4″ 20 Tap

Step 1:

Determine the position of the 1/4-20 tapped hole. Using the tape measure, locate the hole and mark its position with the scribe.

Step 2:

Align the center punch’s tip with the position of the hole to be tapped. To create a depression for the hole placement, hit the rear of the center punch with the hammer.

This will prevent the drill bit from straying away from the center of the hole.

Step 3:

Place the drill bit in the drill. To secure the drill bit, tighten the chuck of the drill. Put a small amount of cutting fluid into the drill bit. Place the drill bit’s tip on the center mark.

Step 4:

Press down on the drill. Drill the hole, pause, and add more cutting fluid to the drill bit to cool the drill and metal.

Step 5:

Place the 1/4-20 tap in the tee handle. Secure the tap completely inside the tee handle. If the tap becomes loosened from the tee handle, it may break during the threading of the metal.

Cut the tap with cutting fluid. Start the tap in the hole while keeping the tee handle level. Thread the tap into the hole by turning the tee handle clockwise.

If the tap becomes stuck in the hole, spin the tee handle 1/4 turn counter-clockwise to release it. Turn the tap into the hole again and again.

Thread the tap through the hole until it reaches the bottom. To remove the tap, turn it counter-clockwise.

Step 6 :

Mount the flapper wheel on the grinder. Remove the burr from both sides of the tapped hole using the grinder.

To verify that the hole is correctly threaded, insert a 1/4-20 bolt into it. If the bolt won’t thread into the hole, clean the tap and apply cutting fluid to the tap and threaded hole.

Tap the hole again to clean the threads.

FAQs

What should also be considered for Drilling 1/4″ 20 Tap?

When drilling any kind of material for tapping, decide ahead of time whether you will tap with 50 % or 75%. This may vary depending on the hardness of the material, so if you can drill through a scrap piece first, you will have a better sense of how to tap.

How to read a drill bit size?

Drill bits are available in fractional, metric, wire gauge number, and letter dimensions. Metric measurements are in millimeters, whereas fractional measurements are in inches.

The letter and wire gauge systems correspond to tool sizes that increase as the wire gauge decreases from #107 to #1 and then from A to Z. The decimal equivalents of the dimensions are provided in English and Metric units.

How to know which size of a drill bit to use?

Place the drill bit’s shaft in front of the screw. You should only be able to view the screw’s threads.

The drill bit is too large if you can’t see the threads. The bit is too tiny if you can see too much of the screw.

How to convert and find equivalent bit sizes?

You may either use the drill chart or perform the arithmetic yourself to convert sizes.

  • To convert millimeters to inches, multiply by 0.039.
  • In  converting  inches to millimeters, multiply by 25.4

Moreover, a drill bit size gauge is another option for easy-to-fit sizes. These helpful cards may help you quickly determine the size bit you’ll need depending on the screw or hole size you need to drill out.

IRWIN Drill Bit Gauge, 1/16-to-1/2-Inch, 29-Hole (12092)

How to determine the drill size for a tapped hole?

The diameter of the tap-drill is equal to the nominal diameter minus the thread pitch. Using this simple method, you can easily determine appropriate tap-drill diameters.

For a 3/8-16 thread, for example, the drill size is 0.375 0.0625 (pitch) = 0.312 in.

Conclusion

The appropriate size drill bit for a 1/4′′ 20 tap is determined by the thread’s coarseness to be tapped. Remember to check the hardness of the material to be drilled through.

However, according to industry standards, the overall size drill bit for a 1/4′′ 20 tap is a #7 drill bit with a 13/64” shank dimension. When tapping harder materials, try using a 7/32 drill bit.

Always choose ahead of time and test with scrap material if available to have the right tools on hand.