What is a Countersink Bit? + How To Use it

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Many experienced woodworkers use a countersink bit to make projects look more professional. However, newbies may use it incorrectly as they’re unfamiliar with this tool or how it works. 

So rather than second-guessing its real purpose, read along as our resident artisans guide you on utilizing these drill bits to ease your drilling experience.

About Countersink Drill Bits

In most workshops, countersink drill bits are used to make pilot holes. These holes are drilled into the workpiece to create an opening for material fasteners like screws. This method allows woodworkers to avoid wood cracks and splits while drilling.

countersink bit

On top of that, these drill bits create a countersink or V-like shape into the material’s face side. If the screws you use have countersunk heads, they’ll be securely driven and blended with the material. 

What are Countersink Bits Used For? Do I Need Them?

Conceals the Screws

If you drill the countersink bits below the wood’s face, the screw can sit low. After that, you can cover it easily using a filler. Additionally, you can get the bits drilled deeper for wood plugs to hide the screws from sight and give the material a cleaner finish. 

Less Splitting

You may not know, but driving screws directly into the material can lead to wood splitting because of its outward motion. 

Our resident woodworkers highly urge you to make pilot holes using countersink drill bits to prevent this from happening. It provides more space for the screw, allowing it to enter the opening smoothly. 

Stop Tearouts

If you don’t want projects to appear unprofessional, you must ensure that tear-outs won’t happen as you drill. More often than not, drilling screws without countersink bits could crush the wood’s fiber except on selected softwoods. 

tip of countersink bit

Trust us when we say it’s harder to avoid tear-outs on hardwood materials like oak without these bits.  

Strong Joint

As the countersink drill bit can make holes that match the screw’s head, it can connect with the workpiece at an adequate force. Given its better material contact, you can form a strong joint between the wood and the screws. 

Two Kinds of Countersink Drill Bits

#1: Fluted Bit

Fluted bits are the market’s most common countersink drill bits. You’ll encounter them in different sizes and composed of one or more cutting edges. These bits are intended for cutting pilot and conical holes. 

#2: Combination Bit

As its name implies, combination bits can drill pilot and countersink holes simultaneously. It’s also available in different sizes, but this bit works faster as it gets the job done in one stroke.

What Kind of Countersink Bit Should I Use?

Fluted Bit

As we mentioned, you can use fluted bits to make pilot holes. We also suggest using them if you’re handling hard materials.

fluted countersink bit

Combination Bit

As you can bore screws in one go using combination bits, they’re effective tools for plugs and dowel buttons. 

Countersink Bit Sizes

Fluted Bit

When buying fluted bits, we highly suggest checking if it matches your screw’s head. You can’t expect the screw to fit or blend if the countersink hole you drilled is too small or too large.

Combination Bit

Unlike the previous option, combination bits are sold in a complete kit or set. It caters to common screw[1] sizes, so there’s not much to worry about. 

Countersink Sizes

Drill Bit Size (Inches)Screw Size Number Screw Size Number 
(For Hardwood)(For Softwood)
⁹/₆₄ inches#10#12
⅛ inches#8#10
⁷/₆₄ inches#6#8
³/₃₂ inches#6
⁵/₆₄ inches#4

How to Identify the Sizes

You can tell if the drill bit is the right tool for your screw if you hold the bit’s end over the screw you’ll be using. These tools are matched if you can see the screw thread on the sides. 

countersink bit sizes for screws

Drilling Tips to Know

How to Use a Fluted Bit: 4 Steps

Tools and Materials You'll Need

Step #1: Measure and Mark the Drilling Spot

For accuracy, even professional users mark the hole’s location before the drilling process. You can use a pencil and multi-purpose marking tool for this step. 

marking drilling spot

After that, grab the awl multi-tool to indicate where the drill bit should start. Doing this can prevent the bit from wandering away from the material.  

Step #2: Start Drilling the Pilot Hole

After the measurements and marks, you can finally drill the pilot holes to accommodate your screws later. 

However, you don’t have to drill as deep as the entire screw’s length. You can use painter’s tape to mark how far the drill should go. 

Step #3: Start Drilling the Countersink Hole

If you followed our previous advice, you already have the right fluted bit that matches the size of the screw. You can follow through by drilling the hole until the screw’s head is flushed into the wood’s face. 

drilling on wood

The deeper you go, the more you can hide the screw’s visibility. You can cover the head with filler or plugs. 

Step #4: Set the Screw

Last but not least, grab a screwdriver or any power drill to set the screw into the countersink hole. 

How to Use a Combination Bit: 3 Steps

Tools

Step #1: Measure and Mark the Drilling Spot

Like the previous method, you must measure the exact spot of the holes using the marking tool and pencil. From there, utilize the awl from your toolbox to make a starting point. 

Step #2: Start Drilling the Countersink Hole

As long as the sizes match, you can adjust the drill bit to align with the length of the screw. You can also tighten the screws via a hex wrench or chucking the drill bit. 

drilling with a countersink bit

As you drill, don’t forget to check if the hole is deep enough for the screw’s head to flush. However, you can always hide it using wood plugs or wood fillers

Step #3: Set the Screw

Finally, use any screwdriver or power drill to insert the screw into the hole you bore. 

Driving Countersink Screws

  1. Choose between a screwdriver and a power drill.
  2. Don’t forget to set the torque properly to prevent tightening.
  3. Never drill too fast. Drive the screw slowly.

Ways to Hide Countersink Screws

You can drill the countersink a bit deeper when trying to hide screws for a finer finish. By doing this method, the screw’s head will be out of sight. 

countersink bit sizes

You can drill as deep as below the wood’s surface so that you use filler or plugs after driving the screws. 

FAQ

What can I use if I don't have a countersink bit?

If you don’t have a countersink drill bit, you can use a normal drill bit with the right size. Before drilling, you must ensure that it’s a bit larger than the screw’s head. 

Are there self-countersinking screws?

Yes, there are self-countersinking screws. These types of screws eliminate any need to bore a pilot hole. 

Conclusion

After learning to use a countersink drill bit, avoiding incorrectly placed screws won’t be as tricky as before. 

On top of that, trust our resident woodworkers when we say that this method makes your work appear more professional and pleasing to the eyes. It also prevents cuts and scratches caused by protruding screws. 

Robert Johnson is a woodworker who takes joy in sharing his passion for creating to the rest of the world. His brainchild, Sawinery, allowed him to do so as well as connect with other craftsmen. He has since built an enviable workshop for himself and an equally impressive online accomplishment: an extensive resource site serving old timers and novices alike.
Robert Johnson
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