What Is Countersunk Screw?
Countersunk screws (also called flat-head screws), are a type of screw that are intended to rest flush, or even slightly recessed, with the object or surface in which it is fastened. Countersunk screws can be simply recognized by the flat head, which allows the screw to sink into the objects or materials.
They are called “countersunk screws” because they sink into objects and surfaces. They consist of a flat head that tapers down the shaft, so when inserting a countersunk screw into an object or surface, the head sinks into the material, and becomes flush to the surface.
Most of the screws that you see in any work are going to be round headed or semi-round headed. Countersunk screws for flat headed screws act differently in context of design, which is considered flat headed, but would need to have the same exterior helical ridges and spin into the material.
Why Countersunk Screws Are Used?
Countersunk screws are utilized in numerous fastening applications. You will often see them used to hold doors to frames, for example. With traditional screws, the head of the screw will stick out. If you close a door that is secured with screw heads sticking out, you stress the door and the frame.
Countersunk screws are a solution to this problem, as they allow a door to sit flush against a frame. The head of countersunk screws is completely submerged, so there is a smooth and level contact between the door and the frame.
Countersunk screws also can be used in many other woodworking and joinery applications. Because the heads sink, they can be hidden with a cap, or filler material.
Once a worker has driven a countersunk screw into an object, or surface, the worker can then cover it with a cap or filler. This is not possible with other screw types since the head sticks out.
What Is a Non-Countersunk Screw Head?
A non-countersunk screw head, by contrast, protrudes above the surface into which it’s installed. That is; it does not sink into the surface of the workpiece, as a countersunk screw would.
Non-countersunk screw heads are flat, and do not taper at their transition to the shank. Non-countersunk screw heads will have a narrow shank, then head that is wider.
Non-countersunk screws can only be installed up to the head without tapering. When the head reaches the surface of the workpiece, the installation will stop, thus, the head prevents any further installation into the workpiece.
Non-countersunk screws are also used in woodworking. In some cases, these screws are better than countersunk screws, since they less likely to cause stress on the workpiece. The tapered area on a countersunk screw is wider than its shank.
Because of this, the tapering of the countersunk screw can cause damage to the workpiece. Non-countersunk screws will not cause damage since they do not taper. When using non-countersunk screws, only the narrowest diameter of the screw (the shank) will be driven into the workpiece.
What Does It Mean to Countersink a Screw?
You might have seen that some of my free wood-working plans mention countersinking screws. If you are relatively new to wood-working, that phrase may not sound familiar, but the process is quite straightforward.
When driving a screw into something, typically, you stop driving once the screw head meets the surface. Countersinking that same screw means that you are going to drive the screw down into the material below the surface.
Types Of Countersink Bits
There are numerous ways to countersink a screw. The ideal method is to use a special bit made for that purpose. There are a few different types.
Predrill Countersink Bit
A pre-drill countersink bit makes a pilot hole for the screw and the conical countersink hole at the same time. This method easily gives you consistency as you move from screw to screw.
Stand-Alone Countersink Bit
Method two can be accomplished with two separate drill bits. One drill bit predrills the hole for the screw. The second drill bit create a cone-shaped hole on the surface of the wood that allows the head of the screw to be below the surface.
This method takes a little more time, but can create cleaner holes. A stand-alone countersink bit can typically be used on both wood and metal, which is an advantage if you use metal and wood regularly.
Quick-Change Countersink Drill Bit and Driver
If you hate to switch from a countersink bit to a driver bit every few seconds, this is what you need! I’m going to purchase this set next time I’m in my local Rockler store. It has a metal sleeve that fits over countersink bits and can be used with the proper drill bit to drive in those screws.
Other types have a countersink bit on one end and a driver bit on the other end. Just flip the bit around and you can switch between operations quickly.
How To Countersink Screws?
Things To Consider: Before you start drilling, there are a few things to consider.
- Do you plan to fill the hole with wood putty or a plug?
- If you are painting your project, you can slightly sink the screw heads below the surface and fill the hole with wood putty for a perfect finish.
- If you are leaving the screw head exposed, you need to drill the hole so the screw head is flush with the wood surface.
- How large is your screw head? Is it flat or rounded? What angle is the underside of the head?
- A flat screw head, with a tapered bottom, is the best option for countersinking screws. Verify that your screw head size matches the size of the countersink bit you plan to use.
- If you are attaching a thin piece of plywood or thin metal to a thicker piece, you may want to try to locate a screw head with a 100° angle head, instead of the common 82º head. The larger angle permits a larger area of contact and with less chance of pull-through.
Step-1. Mark The Hole Position
Using a pencil, mark the location of each hole for your workpiece. If you are attaching two pieces at a right angle as seen below, draw a line marking the center of the board you are going to drill into.
Step-2. Choose The Correct Countersink Bit Size
Match the diameter of your countersink bit to the diameter of the screw you wish to use. If you examine the packaging for the screw it should say what number size it is. Most common sizes are #6, #8, and #10. Also, ensure that the screw has a flat head and a conical shape underneath.
Step-3. Adjust The Countersink Bit Height
Adjust the height of the countersink to correlate with the length of your screws. To do this, insert the corresponding hex wrench into the hole on the side to loosen it. Then raise or lower it to match the depth of screw you will be using in your project.
Step-4. Test The Fit
After creating the initial countersink hole, test-fit the screw and see where it sits. If it sits too high, the screw head will be above the surface of the wood. If it is too low, then it will take a lot more time to fill that hole. By test-fitting on a scrap of wood first, you can get it just right before starting your project!
How To Countersink Without a Bit?
If you don’t have a countersink bit, there are two ways you can create one using standard bits.
Two Drill Bit Method
Drill a hole using a bit the same diameter as the screw you will be using. Use a piece of tape on the bit of the right depth so that you stop at the same height as the length of the screw so as not to go through the material.
Then select a bit slightly larger in diameter than the screw head. Drill a hole for the head of the screw to sit counter-bored just below the surface of the wood or metal.
Yes, the hole you see isn’t the cleanest hole in the world (the one on the left) but is will suffice if you plan to wood fill it later anyway.
Philips Head Bit Method
If you’re out on a job and find yourself without a countersink bit, this method can be used in a pinch. Take your Philips Head bit and place it in the location where the screw would go.
Start the drill and move it in a circular direction, widening the hole each pass until the desired size is reached.
This method produces a surprisingly clean hole (the center one) – although it’s a bit too small. The screw head now is slightly above the wood surface, meaning that using wood filler could never hide it.
Hiding Countersunk Screws
After you’ve finished countersinking your screws, you can leave them as is, or you can make them disappear! There are two different methods for hiding countersunk screws.
Hide Countersunk Screws with Wood Filler
This is the method I prefer to use when hiding screw heads for a project that will be painted. Use whatever type of filler or putty you want to fill the hole, overfilling a bit. Then when the putty is dry, sand smooth and paint your project. Poof, the hole is gone!
Hide Countersunk Screws with Wood Plugs
I have not utilized wood plugs in any of my projects personally, wood plugs tend to be for fine woodworking. I am the slap-it-together style woodworker.
You can always drill your countersink hole deeper or use a counterbore bit to then fill the hole with a wood plug that will blend into the grain. You can also use contrasting wood color or a button to showcase the hole instead!
How To Countersink Deck Screws?
Self-Countersinking Screws
With all of the specialty screws on the decking market , it is really easy to find self-countersinking screws, which can sink into the board easily, and wood will naturally cover back over the specially-designed screw head without a shabby bump on the surface.
Deck Countersink Kit
Should you find yourself needing to countersink the deck screws the old-fashioned way, there are kits you can order that have the pilot bit, countersink bit, and screwdriver. The countersink is slightly larger than normal so it is possible to use a plug to cover the hole.
Countersink Lag Bolts
When constructing a deck, lag screws, and lag bolts are almost always required to fasten the framing. You can install them and leave the head and washer showing, or you can also countersink these.
Firstly, measure the width of the screw part of the lag; then find a corresponding bit. Next, measure the size of the washer you are going to use and find a paddle bit, slightly larger.
To make the countersink hole that will hide the bolt head and the washer, drill the hole for the body of the lag, and then come back, and using the paddle bit, cut the hole deep enough for the washer and the lag head to be below the surface.
How To Countersink Drywall Screws?
The underlying concept of driving a drywall screw to the proper depth is knowing when to stop! This cheap piece of plastic will stop you from going too deep and breaking the paper face, which is mainly where the strength of the drywall is located.
The ideal countersink in drywall is when the screw does not break the paper face and just sinks below the surface. If you try to do this by “eye,” it will usually result in breaking the paper with most of the screws and making the screws sink inside the gypsum.
How To Countersink Screws in Metal?
Although you may not do this often, it is nice to know that almost everything you learned about countersinking screws in wood will apply to metal. The primary difference will be in the type of bits to cut into the metal.
You can find countersink bits that will cut for metal, but these typically do not come with a pilot bit. You will need to find a bit that matches the body size of the screw and drill that hole first.
As with wood, wrap tape around the bit to establish the depth you desire. Then use your countersink bit to drill the conical hole for the screw head.
FAQs
What is the purpose of countersinking screws?
Countersinking is a great way to make the fasteners in your design flush with the parts they’re connecting. It can give a more professional and polished look, making screws look integrated rather than an afterthought. They’re also functional, keeping bolt heads out of the way.
What is countersunk vs flat head screws?
A countersunk screw head, also known as a flat head, has a flat and level head. The aim of the countersunk screw head is to allow the screw to be level, or beneath, the surface it is being screwed into. A bugle screw head is very closely similar to the countersunk screw. It also has a flat head.
What is the difference between a countersunk and a bugle head screw?
The difference between a standard countersunk and a bugle head is that the bugle head has a sort of rimmed conclave on the underside of the flat head. This curved inwardly edge makes Bugle Heads more suitable for soft material, like wood and dry wall.
What is a countersunk screw head called?
Also known as a flat-heat screw, a countersunk screw is a type of screw that’s designed to rest flush with the object or surface in which it’s inserted. They are called “countersunk screws” because they “sink” into objects and surfaces. They feature a flat head that tapers along the shaft.
When to use a countersunk screw?
One of the most common uses for countersunk screws is securing door frames. Other screw types would protrude from the frame, causing ongoing stress between the door and the frame.
How do I countersink a screw?
Start by drilling a pilot hole for your screw so you can thread it in easily without splitting the wood. After that, you can use a countersink cutter to drill a larger hole for the screw head. Once the screw is in place, you can either leave it exposed or conceal it using wood putty!