Wood joinery is one of the most fundamental concepts in woodworking. How do you attach pallet boards together? Why did you join them together in that fashion? Here's a list of common types of wood joints and some examples that may help you when deciding how to build a pallet craft. This is not a detailed tutorial on how to do the wood joints, as some are more advanced techniques. Instead, this is just a tool to help you identify the common types of wood joints you see in builds and hopefully give you ideas for your next project. If you're a joinery pro, PLEASE submit a tutorial on how to do some of the types of wood joints listed in this article.
The Butt Wood Joint
This is probably the type of wood joint we non-pro crafters see and use the most.
It is only two pieces of wood that are pushed against each other – either perpendicularly, such as with a picture frame, or along the same plane, as when we bond several boards side-by-side to make a larger piece of wood (for a tabletop as an example). It’s a wood joint for rough or rustic work. It can be left visible, or it can be countersunk and either filled with wood putty or with wooden plugs. There’s nothing wrong with this joint, but it isn’t automatically a stable or strong joint, mainly if you rely on glue alone.
Let’s use the picture frame as an example. If you were to only glue the end grain of one board to the long-grain of another, even when the glue dried, it would be easy to push the ends and separate the wood joint. So what can we do to make it stronger?
The most common ways to reinforce this type of wood joint are the following:
- Fasteners - nails, screws, and even metal brackets can be used to strengthen the joint.
- Glue added along with your fastener of choice.
- Dowels - drill holes and glue/insert wooden plugs.
- Biscuits - eye-shaped thin pieces of wood that are attached by using a biscuit joiner tool that will cut a half-moon shaped groove in the two boards to be joined. The biscuit is put in after gluing the grooves, and the wood joint is clamped. Biscuits are especially good with plywood and other manufactured pieces and provide a lot of gluing surface in a small amount of space.
- Pocket joinery - such as Kreg joinery tools where holes are pre-drilled to toe-nail fasteners in. This is stronger than just screwing into the end grain, and the advantage is that it can be hidden. Pocket joinery is pretty fast and secure, but you have to have special tools to do it correctly.
However, the other example of making a tabletop out of several boards glued with the grain can be stronger than the wood itself if proper clamping pressure is applied.
Another type of wood joint that falls into this category is the miter joint. Let’s use that picture frame again. Instead of just pushing one straight board against another, if you were to cut the two ends at a 45-degree angle, that’s a miter joint. The advantage is that it provides a bit more gluing surface. The disadvantage, as with all butt joints, is that end-grain of wood doesn’t like to take glue well, so it’s always going to be somewhat weak. Now if you were to make a small, light piece, the new types of glue would probably hold fine, but for a more significant piece, you need to think about reinforcements.
A straightforward and decorative option is to use a spline. A spline is nothing more than a notch cut across the miter joint and either a same-toned wood or a contrasting-toned wood - like a shim - is inserted into the gap with glue. When dried, the excess that protrudes can be trimmed and sanded down flush. This provides added stability - similar to a biscuit, but it’s not hidden.
The Half-lap Wood Joint
If you’re making a piece of furniture where two boards need to be joined in the middle, instead of just the ends, this is a handy type of wood joint to be aware of. A half-lap joint is where a portion of wood is removed from both of the two boards, and they’ll end up fitting together like a puzzle piece. The easiest way to visualize this is to picture chiseling out a 1” wide groove only about half the way through each board. When the two chiseled-out pieces fit, the boards will intersect, and one side won’t protrude more than the other. It gives a nice, finished look to the piece. Since there is material removed from each board, it does lessen the integrity slightly, but it may be worth it. The joined area can be just glued, or fasteners can be added as well.
The Rabbet Wood Joint
This is another dado joint cut along the edge of a board instead of the center of it. You’ll frequently see it used for joining cabinets or for making boxes where two edges need to fit together snugly. A dado set or dado blade is a type of circular saw blade that you'd typically use on a table saw or radial arm saw.
This blade set cuts out a broader swath of wood than a single table saw blade. There are two common kinds of dado sets a stacked dado set and wobble blade.
The Tongue-And-Groove Wood Joint
Have you worked with wainscoting, interlocking siding, or laminate floors before? Then you’ve probably seen a tongue-and-groove wood joint. This tends to be a wood joint used to hold two boards together on their edges, rather than along the ends. One end is curved so that it has a protruding piece (the tongue), and the matched piece is carved with a recession (the groove). They should interlock and fit snugly together.
This type of wood joint can be further reinforced with glues (such as with manufactured products). Sometimes the tongue and groove are cut at a slight angle so that the boards must be attached at an angle and then pushed down to “lock” in place – mainly laminate floors these days. It is much easier to do this with the proper router bits. There are hand-planers that will do this too.
The Dovetail Wood Joint
This is a beautiful and solid wood joint. Think of a fancy jewelry box where you can see where the wood pieces interlock like fingers. No nails or metal fasteners are required typically; only a little glue to help secure it. The notches are precise and may need a few taps to get the pieces to fit together. Some dovetail joints are spread wider towards the end so that once interlocked; they couldn’t pull loose unless they came out in the same direction they were tapped in. These are durable joints, and since they can only be disassembled in one direction, they’re stable and take a lot of abuse. Think of an old drawer. They’re frequently dovetailed, and they survive kids! A similar type of wood joint is a finger joint – these tend to be a dovetail that tapers instead of widens towards the end of the wood.
The Half-Blind Dovetail Joint
When connecting two pieces of wood, probably the most renowned joint is the through dovetail. The through dovetails is strong and beautiful, but there are instances where a through dovetail simply isn't the most aesthetic choice.
For instance, when connecting sides of a drawer directly to the drawer front, one wouldn't want to use a through dovetail joint, as the ends of the tails would show through the drawer front.
In this case, the best type of dovetail joint to use is the half blind dovetail.
What is a Half Blind Dovetail?
The half-blind dovetail is precisely as the name denotes: half of the dovetail joint is visible, while the other half of the joint is hidden. This joint is nearly as strong as the through dovetail but is used in instances such as the drawer front scenario described above.
Creating Half Blind Dovetails:
The traditional method of creating half blind dovetails doesn't differ much from the method of creating through dovetails, but there are some points to keep in mind:
The section of the pinboard that is not to be cut (thus forming the blind portion of the joint), is called the lap. The lap on the board should never be less than 1/8" thick, yet should never exceed 1/3 of the pin board's thickness, to ensure the strength of the dovetail joint.
Cutting half blind dovetails uses the following basic steps:
- Plane the ends of the two pieces of the stock square.
- Mark the length of the tails, which is the width of the pinboard minus the lap. Make a shoulder line at the appropriate length around the tailboard.
- Mark the tails at the desired angle.
- Cut the tails with a Dovetailing saw.
- Remove the waste between the tails using a bevel-edged chisel.
- Using the completed tails, mark the pins on the pin board, aligning the shoulder cuts with the side of the pinboard opposite the lap.
- Cut the pins and clean the waste using a chisel.
- Test the joint's fit and trim more off of the pins if needed.
Using a Dovetailing Jig:
While nearly all router-based dovetail jigs can cut through dovetails, only certain systems can cut half blind dovetails. Keep this in mind when shopping for a dovetail jig system for your shop.
The procedure for cutting half-blind dovetails with a dovetail jig system is pretty much the same necessary procedure.
Mark the depth of cut on the tailboard based on the width of the pinboard minus the lap. Insert the tailboard into the jig and cut the tails using an appropriate dovetailing router bit. Then, following the jig's instructions, mark and cut the half-blind pins in the pinboard.
Half blind dovetails should be assembled in precisely the same manner as through dovetails: dry fit the joints first to verify a proper fit, then disassemble, apply a thin, even layer of glue and assemble the joint. Use a rubber mallet to seat the joint if needed, and then immediately wipe off any excess glue that escapes the joint.
The Secret to Perfect Half Blind Dovetails:
Also as with through dovetails, the secret to half-blind dovetails is to cut the tails, then mark the pins based on the tails. As noted above, never leave less than 1/8" lap on the pinboard, but not more than one-third the overall width of the pinboard. Dry fit the joint after cutting the pins and remove a bit more stock from the pins only if the fit is too tight.
The Mortise & Tenon Wood Joint
It’s one of the oldest types of wood joints around. It’s an exaggerated form of a tongue and groove where one protruding piece of wood fits into a notched piece of another board or timber. The mortise is a square or rectangular hole carved into one board. The tenon is a corresponding piece carved into the joined section. They can be glued, dowelled, or fastened, but some of the oldest wood joints are stable by careful joinery and nothing else. You’ll see a lot of this type of wood joint on trestle tables or on exposed beam work where nails/hardware would detract from the overall look of the piece.
The Mitered Butt Wood Joint
The butt joint is the most basic woodworking joint, where two pieces of wood are butted together (most often at a right angle to one another), but it isn't the prettiest of joints since the end grain of one of the two boards will be visible. When you want a more attractive option, try a mitered butt joint. It won't be any stronger than a standard butt joint, but you won't see the end grain.
Angles Must be Precise:
As in a basic butt joint, the most critical aspect of creating a mitered butt joint is to cut the angles precisely. For this, you'll need a compound miter saw.
The first step is to determine the final angle of the joint and divide that number by two. For a square connection (90-degrees), you'll need to make a 45-degree angle cut on each of the two boards to be joined. If the two pieces of stock are the same width, the two cut ends should match up perfectly.
You can also use mitered butt joints when creating other joints of other angles. For example, if you were making an octagonally-shaped picture frame, each of the eight angles would be 45-degrees (rather than 90-degrees in the previous case). As such, you would cut 22 1/2-degree angles on each end to create the butt joints.
Glue Holds the Joint:
As in a basic butt joint, the glue is the means for holding the joint. However, because both sides of the glue joint will be on porous end grain, you will likely need to use more woodworking glue than when gluing on side grain.
TIP: Be sure to dry-fit your pieces before applying glue, to ensure a proper fit.
For instance, if you're making a picture frame, cut all lengths and angles and cross-check the frame for squareness and make sure that the joints have no gaps before applying glue.
Use Mechanical Fasteners for Strength:
As with a basic butt joint, there isn't a lot of strength in a mitered butt joint. As such, you may wish to strengthen the joint by using nails, brads or screws to give lateral strength to the joint. If using hardwood, remember to pre-drill before installing screws to avoid splitting.
The Dado Wood Joint
Using a dado is a very functional and strong method for connecting two pieces of stock. Once you learn how to cut a dado, you'll find these woodworking joints especially useful when building cabinets or bookshelves.
A dado is a groove cut into one piece of wood into which another piece of wood will fit snugly. For instance, when building a bookshelf using 3/4" thick stock, one would cut a 3/4" wide groove into the shelf standard and then glue the shelf into the groove.
Methods for Cutting Dadoes:
There are a few different methods for cutting a dado. Probably the most common way is to use a stacked dado head cutter on a table saw. This consists of two 8" diameter, 1/8"-kerf saw blades with some 1/8" & 1/16" chippers in between. By adding or removing chippers, you can get pretty much any width groove between 1/4" and 3/4".
Wider dadoes can be cut by making more than one pass through the saw. A stacked dado head cutter set should only be used on a table saw or on some radial arm saws (check the tool's documentation to see if your table saw, or radial arm saw will accommodate a stacked dado head cutting set). Do not attempt to use a stacked dado head cutting set on a circular saw, as this would be extremely dangerous.
Another option is a "wobble" dado set. This is a single saw blade set on an adjustable spindle. Adjusting the blade angle on the spindle will change the width of the dado. While these are much cheaper than a stacked dado head cutter set, the results are far less predictable, and in my experience, rarely acceptable.
I'd resist the urge to buy a wobble dado and save my pennies for a quality stacked dado set. I'm also not entirely comfortable with the safety of using a wobble blade.
Cutting Dadoes With a Router:
Another popular method for cutting dadoes is to use a straight cutting bit on a router. When using a router to cut a dado, keep in mind that you'll want to dial down the bit speed quite a bit and adjust the depth for more than one pass to keep from burning the bit or the wood.
Use a straight edge to guide the router, to ensure a straight path. Be advised that using a 3/4" router bit will cut a dado slightly larger than a 3/4" sheet of plywood (which is 23/32" thick). While 23/32" bits are commercially available, using a 1/2" bit and two passes would provide the desired results.
Points to Remember:
When cutting a dado, try to avoid cutting any deeper than 1/3 of the way through the stock receiving the dado, to keep from weakening the stock. For instance, when cutting a dado in a 3/4" shelf standard, make your dado cut 1/4" into the standard.
Also, there may be times when a dado shouldn't be cut the entire length of the stock. In this event, it may be best to cut the dado on a router table.
Set the fence to the proper width and mark the start and stop points for cutting the dado on the fence with a pencil. Then, after starting the router, slide the stock on top of the head (keeping it against the fence) and ease it down onto the cutter. Slide the stock forward to the stop point, then back the stock up an inch or so before turning off the motor. Wait for the cutting head to stop spinning before lifting the stock off of the table.
The Biscuit Wood Joint
For certain types of woodworking joints such as edge-to-edge joints, miter joints, T-joints and corner joints, there is hardly a better choice than biscuit joints. Properly-cut biscuit joints are strong and accurate, particularly when cutting slots with a woodworking tool called a biscuit joiner (or plate joiner).
What is a Biscuit?
A biscuit is a thin, oval-shaped piece of compressed wood shavings, typically made from beech wood.
When glued into slots precisely cut by the biscuit cutter, and the moisture from the glue causes the biscuit to swell and tighten the joint.
Biscuits commonly come in three sizes:
#0 - 5/8" x 1-3/4" #10 - 3/4" x 2-1/8" #20 - 1" x 2-3/8"
Biscuit cutters should have the ability to precisely cut all three sizes.
What Size Biscuit to Use?
As a general rule, try to use the largest size biscuit possible, as this will provide the most significant amount of strength to the joint. In most cases, use #20 biscuits, but when working on narrower material, switch to smaller biscuits where appropriate.
The most common type of biscuit joints is edge-to-edge joints. This is often used for gluing up table tops of various width boards of the same thickness, where biscuits are used along the planed long edges of the boards.
To glue up a table top of various boards, lay out the boards side-by-side with each board's end grain turned in the opposite direction of that of the previous board. This will help keep the table-top stable when the boards expand or shrink.
Once the boards are in the proper positions, use a pencil to make marks across the joints every 4-6". These will be the centerlines for the biscuit slots.
Next, separate the boards and adjust your biscuit joiner for the appropriate size of the biscuit joint. In the case of edge-to-edge joints, you'll most likely use the large #20 size.
Placing the guide fence on top of the stock (perpendicular to the edge), align the cutting guide with the pencil mark. Hold the fence in place, start up the saw and once the motor is at full speed, smoothly plunge the blade into the stock until you can't push any farther. Then, retract the blade fully and repeat at the next mark.
Once all of the slots have been cut, place a small amount of glue evenly throughout the slots on one edge and insert the biscuits. Then, apply a similar amount of glue into the opposite slots on the other edge and connect the two boards.
You'll want to quickly glue up each edge of the table top and then clamp the entire assembly. Snug the clamps so that all of the gaps close completely, but be careful to avoid squeezing so hard that any glue in the joints is squeezed out. If any glue does squeeze out of the joints, be sure to wipe it off immediately to avoid affecting the finish later.
The Pocket Wood Joint
Pocket joints are nothing more than a screw that is driven diagonally through one board into another. Pocket joints are very similar to dowel joints and mortise & tenon joints. To create a proper pocket joint, the path for the screw must be pre-drilled to avoid splitting the headpiece. While this can be done by eye, an easier method for drilling consistent pocket joints is to use a pocket-hole jig.
The screw is driven through the headboard into the tailstock. No glue is necessary, as the screw will hold the joint securely, but glue would add strength to the joint.
Pocket Hole Jigs:
Improvements in pocket hole jig technology in recent years have made pocket joints not only easy but often preferred in certain applications such as many types of face frames.
There are numerous different styles of pocket joints, but the basic idea is a jig with a machined aluminum guide cylinder is positioned at a precise angle in the jig. The jig is then clamped to the headboard, and a particular bit the same diameter as the hole (with a much smaller bit on the tip) is used to drill through the aluminum cylinder into the headboard.
Once the pocket hole has been drilled in the headboard, the tailboard is clamped into place, and a screw is driven through the pocket hole into the tailboard. If the glue is to be added to strengthen the joint, it should be placed on the mating surface between the tailboard and headboard before inserting the screw(s).
Popular Uses for Pocket Joints:
While the most common use for pocket joints is in face frames, there are many other possible applications. Pocket joints can be used to join edges to make a table or cabinet top. They are also very useful when attaching relatively thick edge banding to plywood or a table top. Pocket joints can even be used to connect angled joints in woodworking projects such as braces for leg rails.
The Box Wood Joint
The dovetail joint is a classic, beautiful & strong method for connecting two pieces of stock. However, there are times where the dovetail wouldn't be the best choice.
For instance, what if you need to connect two pieces of plywood as opposed to hardwood? Using dovetails to attach plywood would considerably increase the chances of delaminating the plywood when testing the joint while dry fitting.
What if you didn't have access to a dovetail jig and a router?
Or perhaps you didn't want to go to the trouble of hand-sawing dovetails? Is there another option other than dovetails to use in your woodworking projects?
Absolutely. A straightforward alternative to the dovetail is called the box joint. As you can see from the image on the right, a box joint is very similar to a dovetail, with the difference being that the fingers in the box joint are rectangular rather than dovetail shaped.
There are a few ways to cut box joints. Of course, you could always do it with a dovetail saw and chisel. Merely pick a width for the fingers that will divide evenly into the width of the stock. In other words, if your stock is six inches wide, a half-inch wide finger would allow for twelve fingers total, six on each piece of stock.
Machining the Fingers:
If you don't want to cut the fingers by hand, there are two ways to machine them. First, nearly all dovetail jigs can cut box joints. While you should check the documentation that accompanies your jig for the exact instructions, the setup is just like cutting the tails of a dovetail joint except that the bit would be a straight-cutting bit rather than a dovetail bit.
An even simpler method is to use a box joint jig on your table saw with a stacked dado set. Determine the width of each finger, then set up the stacked dado set to that width. Set the depth of cut to the same height as the thickness of the stock.
Next, attach a scrap piece of stock to your miter gauge.
The scrap should be wide enough so that, when attached to the miter gauge, it extends past the blade by at least an inch and at least two inches past the miter gauge on the left side.
Verify that the miter gauge with the attached piece of scrap stock is square to the blade, and then run the scrap through the saw.
Next, remove the scrap from the gauge and move it to the right twice the width of the fingers, and re-attach to the miter gauge. For instance, if the fingers (and consequently the stacked dado set) are 1/2-inch wide, you should move the scrap one inch to the right and re-attach it to the miter gauge.
Now, cut a small piece of stock that is the same width as the fingers that will fit into the cut you made in the scrap. However, this piece should be at least twice as long as the width of the workpieces. Attach this piece in the notch in the scrap with a wood screw from the bottom, positioned so that it protrudes forward from the scrap toward the saw blade. This will act as a gauge for cutting the fingers.
Finally, verify that the miter is still square to the blade, and turn on the saw and cut a new notch in the scrap in its current position.
Cutting the Box Joint Fingers:
Now that you have the jig made, grab one of the workpieces and place it on end, firmly against the scrap and up against the little guide you attached to the notch in the scrap. Hold the stock tightly against the scrap piece and run it through the saw. Once it clears the blade, slide the entire assembly back through the blade, taking care to hold the work piece tightly against the scrap. You have just cut the first finger and notch, precisely at the proper width.
Now, with the gauge and workpiece well clear of the blade, move the workpiece to the right and slip the newly cut notch over the little guide piece. Hold the stock firmly against the scrap and cut the next notch in the same manner as you cut the first.
Continue cutting notches until all of the fingers of the workpiece have been formed.
The opposing workpiece is cut similarly, except that the first cut is not made with the stock up against the guide. Instead, the outside edge of this piece should be flush with the outer edge of the dado blade. This can be easily positioned by lining up the outside edge of the workpiece with the edge of the notch in the scrap. Once it is lined up, make the first cut, then proceed using the guide as noted above.
Once all of the fingers on both sides of the joint have been formed, be sure to dry fit the joint. However, if you have built the jig correctly, the joints should be perfect every time.
To assemble box joints, simply apply a thin layer of glue on all joint surfaces and slip the joint together and clamp as needed. This type of joinery works fine for making box-like structures such as drawers. However, you'll need to be a bit more diligent about keeping the box square when clamping than you might need to with dovetails.
Even so, the box joint is a relatively strong and useful joint, one that can be a lot of fun to build. It is not as elegant as dovetails, but certainly very appropriate in some circumstances.