What Is a Countersink Bit (And How to Use It Properly)Thumbnail

What Is a Countersink Bit (And How to Use It Properly)


You’ve certainly seen them, screws that lie beneath the surface of the wood.

Not only does it look good, it’s also a lot safer because the head of the screw doesn’t protrude and you can’t get caught on it with your clothes or hurt yourself.

To be able to place the head of a screw flush with the surface of the wood, a countersink drill bit is needed.

But what is a countersink bit? And how do you use it correctly?
That is what you will discover in this article.

Note: To use a tapered countersink bit, it is recommended to drill a pilot hole first. After that, you can use a countersink to be able to sink the screw into the wood.

If you have no idea what a pilot hole is, or you don’t know how to make a pilot hole and what size, I recommend reading my article, “Is A Pilot Hole Necessary? Clearly Explained For The Best Result!

What is a countersink bit

A countersunk bit is a type of drill bit that allows you to widen the entrance to a pilot hole so that the screw head is flush with the surrounding wood rather than sticking out on top of it.

The countersink cannot be used to drill holes; instead, its unique shape is designed to create shallow, wide holes in which the head of a screw fits perfectly.

If the countersink hole can be made deep enough, a filler can be used to cover the screw head. You can make a screw completely invisible in this manner.

The countersink drill bit has an unusual shape, and deep drilling is not an option due to the unusual shape of this type of drill. Don’t get me wrong, it is possible, but you will need to apply a lot of force to the drill and, most importantly, patience.

If you want to drill a deep countersunk hole, for example, to finish with a plug, there are other options. More on this later in this article.

Countersinks come in different forms, all of which you can discover below, as well as how to use them properly.

What does a countersink bit look like

There are different types of countersink bits, which I will discuss later in this article. For now, I will discuss what a tapered countersink bit that is most commonly used looks like, the one-piece countersinks.

What Is a Countersink Bit - Parts of a countersink bit
What Is a Countersink BitParts of a countersink bit

One-piece countersinks have a short shank topped with a conical tip. One or more cutting edges can be present on this conical point.

The number of cutting edges is normally odd, which ensures smooth running when countersinking. As a result, the countersink will also slip less quickly, and it is easier to use with a hand drill.

Countersinks are manufactured with six common angles, namely 60°, 75°, 82°, 90°, 100°, 110° or 120°, the two most common being 82° and 90°.

The different angles are intended for different applications. Here, you will find an overview:

60° for deburring
75° for rivet heads
82° for countersunk screws US standard
90°, 100°, and 110° for countersunk screws
120° for countersinking sheet metal rivets

When to Use a Countersink Drill Bit

A countersink can be used for a variety of reasons. A tapered countersink bit is a versatile drill bit that can be used to countersink screws beneath the surface or completely hide screws, deburr material, prevent tearing, or eliminate hazards.

Hide Fasteners

By drilling a countersink slightly deeper than the fastener head, you can completely conceal the fastener. To fill the hole, cover the fastener head with woodfiller, and give the appearance of smooth, undisturbed wood, wood plugs.

Deburr Material

Burrs can form when drilling a hole through metal or plastic. A burr is an unwanted projection of material produced by machining. By removing the deburred portion, a countersink can be used to deburr the sides of the hole.

Prevent Tear-Out

A screw’s threaded body cuts through wood as it advances. The threads on the fastener heads have been removed. Instead of cutting the wood, it grabs and pulls the fibers, resulting in a tearing out mess.

Tearing out is especially common when inserting fasteners into hardwoods. For the best results, the countersunk pilot hole should be the same size as the tip of the screw or fastener you’re installing.

Eliminate Hazards

A protruding screw or other fastener on a smooth surface can cause problems. When this occurs on a floor they can pose a tripping hazard. furthermore, protruding screw heads can cause scratches and deep cuts on the hands or you can get stuck on them with your clothes. These risks are eliminated by galvanizing your fasteners.

Types of Countersink Bits

Countersink bits are classified into two types: one-piece countersink bits and combination countersink bits. Fluted and cross-hole drills are two types of one-piece countersinks.

One-Piece

One-piece countersinks are exactly that: one-piece. You saw a picture of a one-piece countersink with the indicated parts above.

To use this type of countersink, you must first drill a pilot hole and then change bits to make a countersink. When you need to countersink a lot, switching can cause you to lose a lot of time.

Fluted or Cross-hole

One-piece countersink bits can be divided into fluted or cross-hole countersink bits. The grooves or tunnels in the bit body allow wood chips to escape during use. When these grooves are on the outside of the bit, they are known as flutes. Cross hole countersunk drill bits eject debris through an angled tunnel drilled through the center of the drill, which gives a much cleaner cut.

What is a countersink bit
What is a countersink bitCross hole countersink
6 commonly used boring tools in carpentry (you should have)
What is a countersink bit – Fluted countersink

Combination

Combination countersink bits can be seen as a one-piece countersink bit that is slid over a pilot hole drill. With the pilot drill the pilot hole can be drilled and thanks to the countersink drill a countersink can be formed in one movement.

Combination countersink bits are great because they save time by not having to switch between the drill bit and countersink bit.

6 commonly used boring tools in carpentry (you should have)
What is a countersink bit – Combination countersink bit

Countersink Size Chart

To help you determine which countersink bit you need, take a look at the table below. This way, you are always sure that you are using the right size.

Drill bit size InchesDrill bit size mmScrew size hardwoodScrew size softwood
5/64 inch2 mm#4
3/32 inch2,4 mm#6
7/64 inch2,8 mm#6#8
1/8 inch3,18 mm#8#10
9/64 inch3,6 mm#10#12
What is a countersink bitCountersink chart

Countersink vs Counterbore. What is the difference?

A countersink and a counterbore are two types that are sometimes confused.

Ultimately, these two have the same goal, which is to make the fastener head disappear into the material or sit flush with the top surface.

What is a countersink bit
What is a countersink bittapered countersink bit
What is a countersink bit
What is a countersink bit – counterbore

The top portion of a countersunk hole is the widest point. The hole’s walls taper down to about the size of the fastener, forming a cone or funnel shape. Countersinks are commonly used to hide screws.

A counterbore’s topmost portion is also its widest point, but the walls do not taper. Bolts, washers, and nuts can be hidden in the resulting flat-bottomed hole. You can check the counterbore’s prices on Amazon here.

How to use a countersink bit

I made a description for both the one-piece countersink bit and the combination countersink bit to describe how to use a countersink bit.

I made a supply list for each of them so that you can gather all of the necessary materials before you begin.

How to use a one-piece countersink drill bit

Here is what you need:

Step 1: Mark where you want to drill.
I always use my Pica marker pencil and Kreg Multi-Mark for marking. These are two of the most frequently used tools in my shop. This will allow you to precisely mark the hole’s location.

You can use an awl to create a starting point for the drill bit to make drilling the pilot hole easier. The owl-created starting point will keep the drill from wandering across the surface of the wood.

Related: How to Make a Cool and Unique Awl from Old Scraps THERE IS NO LATHE!

Step 2. Drill a pilot hole first
To make a pilot hole, choose a drill bit that matches the size of the screw. To know which drill to use, you can view the table with the dimensions of screws vs pilot drills here.

You can use a piece of painter’s tape to mark the depth of the pilot hole. All you have to do is stick it on the drill bit equal to the length of the screw. Don’t worry, you don’t have to be precise, the depth of the hole should just be close to the length of the screw.

Once you have made the mark, insert the bit into the drill and drill the hole until the painter’s tape makes contact with the surface of the wood.

Step 3. Drill the countersunk hole
Choose a countersink that matches the angle of the screw head. Insert the bit into the drill.

Then drill the hole deep enough to make the screw head flush with the surface of the wood. Or drill the hole deep enough to hide the screw head with a filler.

Step 4. Install the screw
Use a screwdriver or drill to drive the screw into the countersunk hole. Make sure the head of the drill fits snugly with the countersink and does not protrude above the surface of the wood. If this is the case, you can remove the screw again and perform all the steps again.

How to use a combination countersink drill bit

Here is what you need:

Step 1: Make a note of the location.
Using a pencil and a ruler, mark the location of the hole. You can use an awl to mark a starting point for the drill and keep it from wandering across the surface.

Step 2: Make a countersunk hole.
Choose a combination bit the same size as the screw. The bit should then be adjusted to the screw’s length.

After tightening the screw with the Allen key, insert the bit into the drill. The combination drill is now ready for use. Make sure the screw is securely fastened to prevent the countersink from loosening and shifting while drilling.

Drill the hole deep enough so that the screw head is flush with the surface of the wood.

Step 3: Tighten the screw
Use a screwdriver or drill to drive the screw into the countersink hole, and you’re done.

Is a countersink bit for wood the same as a countersink bit for metal

Normally, a tapered countersink bit for wood is the same as a countersink bit for metal, but that depends on the material they are made from and the manufacturer’s recommendations.

Some countersinks are better suited to wood than hard surfaces such as metal. However, it is possible to find a countersink that can be used on both wood and metal.

A good tip is to look at the price. In general, a higher price will reveal that higher quality materials were used to drill in both wood and metal.

Can You Countersink With a Regular Drill Bit?

A standard drill can be used in place of the countersink bit, but the quality and outcome will be inferior.

This technique yields the best results when drilling in softwood. However, keep in mind that there is always the risk of splintering and tearing around the screw head. Avoid using a standard drill bit when drilling in hardwood. If you want a smooth, beautiful surface, I still recommend using a countersink drill.

The only time you’d use a wood drill is to replace a counterbore. When I want to disguise a screw with a dowel, I use this. With this, I can drill a deep countersink hole into which a dowel can be easily glued.

Best countersink bit set (one-piece countersink)

6 commonly used boring tools in carpentry (you should have)
What is a countersink bitIRWIN Tools 1877791 Set of 5 countersink bits
What is a countersink bit
What is a countersink bit – KEO 53513 Cobalt Steel Single-End Countersink
What is a countersink bit
What is a countersink bit – KEO 53518 Cobalt Steel Countersink Set

Best countersink bit set (combination)

6 commonly used boring tools in carpentry (you should have)
What is a countersink bitSnappy Quick Change Conical Drill Bit Set
What is a countersink bit
What is a countersink bit – Snappy Tools Quick-Change 5-Pc. Countersink
What is a countersink bit
What is a countersink bit – FTG USA Wood Countersink Drill Bit Set

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