What Size Of Drill Bit Should Be Used For A 1/4″ 20 Tap?

It’s already back-breaking to do your home repairs yourself in the first place. Then, you waste time in a hardware store trying to figure out what drill bits you’ll need for a specific tap size. We won’t put you through that! You can easily scroll down and look at all the options that can be used for a 1/4” 20 Tap. But before that, you’ll benefit from learning about tap drill sizes and why it’s so essential to pick the right one!

What is tap drill size?

A good tap drill size is 75% to 90% of the thread. What is a thread, you may ask?

Well, if you ever look at a screw, you’ll realize that it has these 3-dimensional rings on its length. These rings are called threads.

The measurement of these threads determines the screw size.

Since you’re here looking for a 1/4” 20 tap, let’s begin with breaking that measurement down.

1/4” represents the major diameter of the screw. The major diameter is a measurement of the largest circumference of the screw. We can also refer to them as thread peaks.

20 represents how many thread peaks there are in a single inch.

Now that we’ve determined how a screw size is measured and determined, we can go ahead and figure out the best tap drill size for it.

If a tap drill size is roughly 75% to 90% of a threaded screw, then the following drill bit sizes will be perfect for your 1/4” tap:

drill

Drill Bit Size For A 1/4″ 20 Tap

Drill BitScrew SizeDrill Bit Size
#71/4″ 20 Tap13/64″
#31/4″ 28 Tap7/32″
  • A 13/64” tap is 80% the diameter of a 1/4” tap. You can look for the 13/64” drill bit size or #7 -which is what it is also called.
  • 7/32” is roughly 87% of the diameter of a 1/4” tap. Because there are more threads in a given inch in a 1/4” 28 tap, going for a slightly larger drill bit size will ensure a stronger hold while tapping. You can also look for the #3, which refers to a 7/32” drill bit size.

Why must a drill bit be only 75 to 90% of a tap?

Contrary to drilling or simple screwing, tapping is a procedure where a drill bit makes a hole slightly smaller than the screw size. A slightly smaller clearance hole ensures that most of the material is removed from the hole. So, when a tap goes in, it takes the pressure of making threads. It allows the tap to go through and make threads just the perfect size for the screw to be fastened in. A tap drill bit 75 to 90% of the screw size will always favor you in all your tapping endeavors. Especially those that involve tough materials like steel.

Best drill bits for a 1/4” 20 tap

Now that you understand what drill bits you’ll require for a 1/4”20 tap, you can move on to purchasing the sturdy piece of equipment. We’ve picked some great options that would make a great addition to your hardware toolkit at home. Check them out below.

Irwin Drill and Tap Set inclusive of 1/4” 20 Tap and 13/64”

Since you stumbled upon this article looking for a drill bit for a 1/4”20 tap specifically, we’re starting our recommendations with this duo. It’s a high-speed stainless steel drill bit of 13/64” that comes along with its matching tap. Its affordable price and reputable brand name, that’s been around for more than a century, are probably what makes it Amazon’s top choice as well.

Pros

  • We love buying products from American companies.
  • Irwin was established in 1885 and has been around for a long time.
  • More than 400 positive reviews on the product
  • It worked well for the purpose.

Cons

  • Some people have gotten the wrong product, although that may be Amazon’s fault.
  • It seems Amazon has a tendency to screw up these orders at the warehouse.
Irwin Tools
430 Reviews
Irwin Tools
You can trust Irwin.

Bosch CO14B 14PC Cobalt M42 Set

Suppose you’re looking for a heavy-duty drill bit set that you can keep handy around the house. In that case, this Bosch 14-piece drill set will have you drawing the value of your money for years to come. You don’t know when one of the 14 pieces will serve its purpose and which of your home improvement projects! Nonetheless, these sturdy m42 alloy materials infused with 8% cobalt alloy are 10 times more durable, which is why we recommend them. They can pierce through various materials such as stainless steel, cast iron, titanium, hardwood, etc. They’re also highly tolerable of high temperatures, inevitably making them last 10 times longer than standard drill bits.

NameBOSCH CO14B 14 Pc.
Item Weight‎1.06 pounds
Material‎Stainless Steel, Cobalt
Package Dimensions‎8.86 x 4.49 x 1.65 inches

Pros

  • Bosch is another trusted name in the space.
  • You get some very good drills for the price.
  • The delivery came fast.

Cons

  • A few of the customers had drills that may have had manufacturing errors.
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BOSCH 
4,012 Reviews
BOSCH 
BOSCH is a trusted name in home improvement.

Irwin 29PC Set M35 Cobalt Alloy Steel

If home improvement projects are a regular thing for you, then investing a little more than usual would make sense. In this case, we’d recommend you get your hands on this 29-piece drill set by Irwin. It’s made of 5% cobalt steel resistant to higher temperatures making it an overall more long-lived set, perfect to have in your hardware kit at home. The price is a bargain for a name like Irwin and a number of pieces that will suit most of your needs.

NameIRWIN Drill Bit Set
Finish TypeCobalt Alloy Steel
Item Dimensions LxWxH‎12 x 7.5 x 4 inches
Material‎Stainless Steel, Cobalt
Pieces29
Tool Flute Type‎Spiral

Pros

  • It’s a great gift.
  • We love the set.
  • After using it, it seems like another durable set from Irwin.
  • There’s free delivery with Prime.

Cons

  • It’s quite a bit more pricey.
  • Your husband may never leave the garage if you give him this.
Irwin
1,813 Reviews
Irwin
Here's a bigger set from Irwin.

Bosch BL2140 13/64” Black Oxide

You came here for a drill bit that can be used for a 1/4” 20 tap size. You figure that a 13/64” is the drill bit you’ll need. Now, you want to grab that and leave. If this sounds like you, click on this link. It’ll lead you to a single 13/64” drill bit that is the best in its price range. Black Oxide is a treatment process where a regular high-speed drill bit is put through excessive temperature to extend its life by 50% more. The treatment makes them tolerant of rust and other wear and tear. The black oxide drill bit is perfect for hard materials such as carbon steels and alloy steels, along with softer metals such as copper, aluminum, plastic, PVC, and wood.

Pros

  • This Bosch product is shipped for free with Prime.
  • We love Bosch.
  • The corrosion resistance of the black oxide is great.

Cons

  • Make sure it’s the drill bit you need.
BOSCH 
542 Reviews
BOSCH 
Get this black oxide option from BOSCH.

Drill America’s Cobalt Extension Drill Bit

Last on our list of recommendations is this Drill America’s Cobalt Extension Drill bit which is 6” in length. So, if you intend to buy a drill bit to focus on drilling deeper holes, you know this will be your best bet. The single Cobalt drill bit may be your hardware toolkit’s first piece of equipment. But with its durability, it may as well be the last one standing. It can drill through tough materials such as aluminum and lighter materials such as sheet metal, wood, or plastic. Lastly, you won’t need a center punch with this drill bit because the 135° split point tip prevents the drill from moving.

Pros

  • Cobalt offers great products.
  • Amazon lets you choose exactly the size you want from the listing.
  • The product is of great quality.

Cons

  • Some people have received the wrong product.
  • You might overextend yourself with DIY projects.
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Cobalt Aircraft
1,825 Reviews
Cobalt Aircraft
It comes in either 6 or 12 inch-lengths.

What To Consider

man using a drill

Like any other skill, drilling and tapping require due diligence to get the job done right. If you’re a beginner, we suggest you look at the following tips before you dig into your new DIY project. Or shall we say drill in?

  • Before you start tapping, you’ll drill a hole. That hole needs to be as square as possible, meaning as perpendicular to the floor (which is a flat surface) as possible. Now, if you’re using a machine, that’s fairly easy to do. However, if you are doing it manually, you may or may not get a straight and usable tap. In this case, consider using a tap guide.
  • Other than a drilling machine, a tap, and a screw, there are other things you’ll need. You’ll need a center punch to prevent the drilling machine from moving and accidentally piercing the wrong spot. This center punch will be used in combination with a hammer. You’ll also need a ratchet, a specific tap holder, or a T-style handle to rotate the tap manually.
  • Besides the hardware, you’ll need some equipment that can deliver water pressure. Though it is not necessary, it does help to clean out the hole from cut-out waste material. You’ll also need to use an oil-based lubricant called “cutting fluid” to smoothen the tapping process.
  • Practice makes perfect. If you are a beginner, we advise you to start with smaller, less significant projects and slowly move towards bigger agendas.

How To Drill

Assuming that you don’t have a drilling press at home, here are the steps to manually drill and tap a hole and secure it with a bolt:

Step 1: The first step is always to mark where you want the hole drilled. Don’t be overconfident. Use a marker to create a small dot wherever you’d like the screw to go.

Step 2: Use a center punch and hammer. Place the tip of the center punch on the dot you created, ensuring it is as perpendicular to the floor as possible. Although drilling the hole straight is more important (next step), it’s always a great idea to start the hole right as well.

Step 3: Attach your drill bit to the drilling machine and place it on the tiny dent you just made with the center punch. Notice how the dent prevents the drill machine from moving? Start drilling the hole, taking care that the hole is as perpendicular to the floor as possible. Use a tap guide if needed.

Step 4: Once the hole has been drilled, use some water pressure to get rid of the excess gunk that has been cleaned out from the hole.

Step 5: The hole has been made. Next, the tap needs to be screwed in to create the threads of the tap. Next, get the tap started by starting to twist the tap into the hole. Use a T-style handle, ratchet, or another tool to rotate the tap. You’ll need to apply some downward pressure to start the tap.

Step 6: Once the tap has been started, it’s a good idea to remove the tap to pour in some of that cutting fluid you have. Then, place the tap and start twisting again.

Step 7: As you are twisting and tapping deeper into the hole, you’ll start to feel some resistance. It is because the chips are getting accumulated in the hole, making it harder and harder for you to rotate the tap.

It is the right time to start pecking. Pecking is the process that allows the chips to break off and cool down while tapping. Twist the handle a half-turn forward and then a quarter-turn in the opposite direction. Keep repeating this process until the entire hole has been tapped.

Step 8: Once the hole has been tapped, the screw should go right in and be secured.

That’s it! You’ve successfully tapped a hole and secured it with a bolt. It ensures a stronger hold that will stay put for years. It will result in tighter joints, and the screw heads won’t be poked out easily.

How To Use 1/4″ 20 Taps

drill bit

The 1/4”20 taps are some of the most common taps that are used. It is because their thread count and diameter fall fairly in the middle on the chart of all drill bits. The diameter is neither too small nor too large. It is perhaps why they’re used in more general, day-to-day situations. Usually, the larger the diameter of the drill bit, the slower you’d want your machine to make the hole. For 1/4” 20 taps, we recommend using the preferred drill bit at a slow to medium speed. Other than that, there is barely any difference in how a 1/4” 20 tap or any other tap is created.

FAQ

What size hole do I drill for a 5/16-18 tap?

The preferred size for a 5/16”-18 tap is 17/64”. You can also search for an ‘F’ labeled drill bit.

What size hole do I drill for a 3/8-16 tap?

To drill a 3/8-16 tap, you’ll need a 5/16” inch drill bit. It is also called the F or G or numbered 88 in a full drill set.

What size hole do I drill for a 10/32 tap?

You’ll need to get your hands on a 5/32” drill bit to make a 10/32 tap. You may also look for a drill bit number 21 in the set.