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edge

Mitered Edge Joints

Edge miter joints offer the ability to completely hide the end grain of the joined pieces, providing a smooth, clean surface to view. The largest problem with miter joints is that they are very difficult to assemble. There are, however, some variations that offer some assistance in assembly.

Glued Edge Miter Joints

Edge miter joints actually expose more wood surface, and therefore the glued joint produced can actually be stronger than a glued butt joint. If more strength is required, you can use small glue blocks, or a continuous glue block. Cut these blocks so the grain runs in the same direction as the pieces they are going to join, so that the two boards and the block expand and contract identically.

Fastened Edge Miter Joints

Using some sort of mechanical fastener such as screws or nails can hold edge mitered joints together, however this can ruin the esthetics of a piece, unless the fastener can be painted over or camouflaged.

Biscuited Edge Miter Joints

Using biscuits in combination with an edge miter joint is an ideal way to have an easy assembly process while having the beauty of nearly-invisible miter joints. The biscuits don’t make the joint stronger (in fact, they can weaken it), however this is a small price to pay for side-stepping the frustration of assembling edge miter joints.

When the joint is assembled, the fit of the biscuits will determine how well the joint keeps its shape during glue-up. By choosing a biscuit that has a snug fit into the biscuit slot, you reduce the sideways movement that can lead to misalignment under clamping pressure. You can improve this by placing the biscuits even closer, as close as 6 inches if required.

Splined Edge Miter Joints

A full-length spline is a convenient substitute for a biscuit jointer, and can even be more accurate. A hardwood spline is ideal, but if you intend to use a hardboard spline, measure its thickness before making any cuts: hardboard is often narrower than its stated dimension. Cut the slot into both pieces of wood no more than 1/3 in from the inside corner. Cutting it any closer to the point will leave very little wood intact to give mechanical strength to the joint.

Remember, a spline will not increase the strength of the joint, however it can make the joint weaker. Its primary purpose is to provide positive registration for the assembly and clamping process

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edge

Face-To-Face Butt Edge Joints

These joints are the simplest of all edge joints. Their primary purpose is to produce wood stock that is thicker than can be economically purchased by gluing together two or more flat boards.

The key to successful face-to-face joints is to have the surfaces flat and clean. When the two pieces are glued together, any voids between the pieces may be visible at the edge, and will reduce the effectiveness of the glue holding them together.

An important precaution to note is that attempting face-to-face joints with different wood species is a recipe for disaster, and should only be attempted when attaching a thin layer to a heavy/stable layer. An example would be to apply a veneer to a plywood base. This is because the different species of wood will expand and contract at different rates, and will cause the wood to warp or ripple.

No mechanical fasteners or fancy joints are required for a successful face-to-face joint.

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edge

Edge-To-Face Butt Edge Joints

The joints used to connect the vertical components of cases, cabinets and furniture require strength and often a measure of ease of assembly. The mating edges are long grain to long grain and are therefore present the strongest joints. And since the grain of the mated surfaces run parallel to one another, there is no worry regarding cross grain joint instability.

Glued Edge-to-Face Joint

This joint is the simplest to form, since all you require are two pieces that are butted together. If the exposed end grain contrasts significantly with the exposed face of the glued-on piece, the appearance may suffer, but for most woods this will not be much of an issue.

Care must be taken to carefully align the two pieces, since any misalignment or warping in the woods can reveal a slight lip along the edge. This can either be planed or sanded off, or it can be hidden by adding a v-groove created by adding a bevel to the edge of the two pieces.

Fastened Edge-to-Face Joint

Fasteners can be used instead of, or in addition to, glue. Clamping may only be required until the fasteners are attached, after which the clamps can be removed. The fasteners will provide enough clamping force to hold the joint until the glue, if applied, can cure.

Note that for most solid wood joints, mechanical fasteners are not required.

Biscuited Edge-to-Face Joint

Biscuits offer the benefit of aligning pieces during the assembly process. Well aligned biscuit slots can produce a project that is quick and easy to assemble. Mis-aligned slots, however, can lead to raised edges that may be troublesome to remove or sand smooth.

Once again, please note that biscuits do not offer any mechanical strength. Their only purpose is to aid in the assembly of the project. In fact, biscuits are weaker than most woods they are used in joining.

Splined Edge-to-Face Joint

A splined joint is essentially a full-length biscuit. Both parts have a groove that accepts a spline. Variations are a through spline, where the spline is visible when viewed from the end of the wood, or a blind spline, where the spline slot has been cut short, and no spline is visible from the end of the joint.

Splines do not offer much strength, however they can be a great aid in speeding the assembly of a project.

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edge

Edge-To-Edge Butt Edge Joints

Many woodworkers find it difficult to believe, however the simple glued edge joint is remarkably strong. Having a good clean and flat edge mating with another similar flat edge produces a joint that is just as strong as the surrounding wood.

The use of joining devices such as splines, biscuits, dowels or keys can actually weaken some joints especially when the material of the device is weaker than the wood to which it is attached. Though they do not impart any strength to the joint, these devices do offer one important advantage: They give the woodworker a handy alignment device that can speed assembly, or maintain alignment during the gluing and clamping process.

Biscuited Edge-to-Edge Joint

Biscuited joints use a series of small slots cut into the edges of both boards to be joined, into which small oval or disk shaped piece of wood or other fibre which are placed. The biscuits maintain an almost perfect surface alignment between the two pieces of wood, yet allow for end-to-end movement between the two pieces. This end-to-end movement helps to make up for slightly mis-aligned slots in adjoining pieces.

Use the largest biscuit that will fit the slot, since a loose biscuit will allow the two wood pieces to drift. It is the stiffness of the biscuit in the slot that gives the alignment assistance that you are looking for.

Splined Edge-to-Edge Joint

This is a variation of a biscuit joint. Instead of using numerous smaller biscuits, splines are essentially a single long biscuit used to align the two pieces. The spline is a piece of plywood or hardboard that is placed in a slots that are cut in the adjoining edges. These slots can be stopped so they do not show if the ends are to be exposed. One thing to keep in mind is to ensure the spline is slightly narrower than the depth of the slot. Making the spline exactly the depth of the slot can lead to splitting of the wood as the surrounding wood shrinks, but the hardboard spline does not (hardboard does not shrink in the same manner as hardwood). A gap of 1/32 (1/64th on either slot) is sufficient to prevent this problem.

Dowelled Edge-to-Edge Joint

Dowelled edge-to-edge joints are another variation on the biscuit joint, but use dowels instead of biscuits. The dowelled joint is prone to errors associated with the difficulty in drilling perfectly perpendicular holes in the narrow edge of panels. This problem can be managed through the use of specialty drilling rigs that drill the alignment dowlel holes in a regular pattern, but these machines are beyond the reach of most hobyists, and other simpler techniques produce similar or better results. As with splines, ensure that the holes drilled for dowels are slightly deeper than the dowel is long.

Butterfly Key Edge-to-Edge Joint

Butterfly keys are a traditional japanese jointing technique, and it provides a very decorative way to edge-join boards. It adds visual appeal to the joint, and depending on the size of the key, the key can be used without adding glue to the joint which offers the possibility of disassembling the boards.

The keys themselves can be made of wood, or even from certain metals such as brass. Note that certain metals are not suitable for use because they will rust in the presence of the natural moisture in the wood.

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edge

Butt Edge Joints

The three cornerstones of edge joints, commonly referred to as “butt joints” are the Edge-To-Edge, Edge-To-Face, and Face-To-Face.

Each of these joints are formed by when each piece of wood is machined straight and square before being fixed to its mate.

  • Edge-to-edge – Where the narrow surface of one piece is joined to the narrow surface of another piece. These joints are commonly used to create wide boards out of smaller pieces.
  • Edge-to-face – Where the narrow surface of one piece is joined to the wide surface, or face, of another piece. These joints are often called corner edge joints since they are used in connecting the columns or vertical components of cabinets to each other.
  • Face-to-face – Where the wide surface, or face, of one piece is joined to the face of another piece. These joints are primarily used to create thicker pieces of wood from thinner stock. You would use these joints to form bedposts or thick table legs.
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case

Rabbet Case Joints

A rabbet is a recess cut across the end or along the edge of a board. Essentially it is a dado that has one side off the end or edge of the board.

Rabbet joints usually only present end grain to long grain surfaces for gluing, and since this is a relatively weak situation, rabbet joints should be supplemented with fasteners.

Rabbet joints are primarily found at the corners of cases, such as between drawer sides and fronts, or top-and-bottom to sides of vertical cases.

When referring to rabbet joints at the end of a board, the depth is the distance measured from the face of the board, and the width is the distance measured from the end of the board. The cheek is the face formed on the tenon produced by the rabbet, and the shoulder is the face with end grain inside the portion that was rabbeted.

Single-Rabbet Joint

This is the most basic form of rabbet joint. It is formed by having the rabbet on only one board, and that rabbet is the full width of the mating board. The depth of the rabbet is usually at least one half of the width, and the deeper it is made the less end grain will be visible. Taken to an extreme, the depth can be such that only a thin veneer strip remains to cover the width of the mating board, but then the joint is almost a butt joint since the rabbet lip no longer provides structural support, only an aesthetic veneer to cover end grain.

Double-Rabbet Joint

When both pieces recieves a rabbet it is referred to as a double-rabbet joint.

Mitered Rabbet

Mitered rabbets provide the appearance of a mitered corner, while providing positive registration for easy clamping and assembly. Once assembled, this joint also provides additional resistance to shear and racking.

To construct mitered rabbets, one board receives a rabbet that has a depth that is (usually) half its thickness and a width the full thickness of the mating board. The mating board would have a rabbet which is the same as its mate’s depth, but only half the width. The remaining tenon is mitered.

Mitered Rabbet With Dowels

A further variation with a mitered rabbet is to introduce dowels or biscuits to further lock the two boards together. Drilling perfectly aligned holes is not possible without a jig or appropriate boring machine, but if it is available the creation of the required holes is a simple process. The benefit the dowels provide is positive registration during the assembly and glueup phase, and it also adds considerable resistance to joint separation.

Dovetailed Rabbet

If one rabbet is cut with an angled shoulder and the other board with a matching angled cheek, the two boards join with a dovetail shaped joint. This is slightly more resistant to racking than a conventional rabbet joint.

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case

Multiple-Tenon Case Joints

Mortise-and-tenon joints are usually considered frame joints, but they serve an important purpose in case construction as well.

Multiple-tenon joints for case construction are primarily used for center supports, and seldom, if ever, for the edge of the case. Because of this, the joint has two primary functions: to support the load that might be placed on the board, and to lock the board in place to prevent it from moving. At first look, a multiple-tenon joints resemble blind stopped dado joints, however the multiple-tenons offer some advantages. The first is that board with the mortises is not weakened from having a full-length dado cut through it as in the dado joint. The second is that the multiple tenons add more gluing surface area. And finally multiple-tenon joints provide positive registration for board placement to keep the board from shifting. A convenient side-effect of that increased gluing surface area is that the joint can be used in situations when it needs to hold the case sides together instead of just resting in position.

The tenons can be made either blind (not visible from the surface of the joint), or through (where the tenons are visible from the exterior of the joint). Through tenons are traditionally secured in place using a small wedge that is inserted into a cut that is made into the end grain of each tenon. This wedge can even be made with a contrasting wood to add visual detail, or it can be made from the same wood so as to not draw attention to the joint.

The tenons of multiple-tenon joints are customarily the full thickness of the stock, providing incredible strength when used for shelving. As the board becomes wider, more tenons should be used to provide more distributed support. In this respect, multiple-tenon joints are similar to box joints except they are located in the center of boards instead of the end of boards.

Twin-Tenon Case Joints

One variation of the multiple-tenon case joint is to use a pair of mortises and tenons. Visually, this gives the joint the appearance of a multiple-tenon joint being constructed on a blind dado, and it gives some of the same benefits. When the board is placed in the mortises, the load rests on the dado portion, while the tenons hold the board in place and prevent it from being pulled out of the joint.

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case

Multiple-Spline Case Joints

Multiple-spline joints are created by cutting slots in both pieces then gluing the joint together with separate splines inserted in the slots. Where the mortise-and-loose-tenon joint has a floating tenon that is oriented from edge to edge of the board, the multiple-spline joint has splines oriented from face-to-face, giving the appearance of box joints. And like box joints, multiple-spline joints can be easily formed on the tablesaw. The splines also offer plenty of long grain-to-long grain gluing surfaces to form a strong bond.

Many variations on the multiple-spline joint exist without changing its basic characteristics. The splines can be of virtually any length or thickness or can even be different lengths and thicknesses. The splines can be evenly spaced or they can be arranged in some form of pattern. The splines can be made of the same material as the boards being joined, or it can be made of a different, contrasting material. The thing to keep in mind is that the eye will search out a pattern, and if the arrangement does not reveal a pattern, the observer may have difficulty accepting the design.

Half-Blind Multiple-Spline Joint

If the spline is not visible from the front but is visible from the side, it is a half-blind joint. To form this joint, the front panel receives stopped grooves, similar to the creation of half-blind dovetail tails. The mating board receives the normal slotted treatment for multiple-splines.

One variation is to create the slots on the mating board less than full thickness, and make the slots on the front panel the same depth. This will create a multiple-spline joint that is visible from the side, but not visible from the front or from the inside.

Full-Blind Multiple-Spline Joint

Whereas the traditional miter joint is relatively weak due to its end grain-to-end grain gluing surface, inserting multiple splines into the joint greatly increases the long grain-to-long grain glunig surface which strengthens the joint. The full-blind multiple-spline joint has the appearance of a simple miter joint, but is strengthened and reinforced by the integral splines.

Though this joint appears difficult to manufacture, it is relatively simple with the use of a router and appropriate jig. It is cut similar to making dovetail tails on two panels, then inserting appropriately sized splines during the glue-up process. Accuracy is critical because the alignment of the slots on both boards must match.

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case

Lock or Locking Case Joints

Primarily constructed with the aid of a router, lock joints are variations on dado-and-rabbet joints. Their primary use is to attach drawer fronts to sides, or in locations where one face of a case must resist being pulled away. Regardless of the construction technique, precision cuts are required to ensure this joint mates correctly, but if done correctly it offers significant strength.

Simple Lock Joint

Simple does not refer to the ease of construction, but refers instead to the fact that the joint resists opening in only one direction. Note that the drawer front can not be pulled off since the side holds it in place. However, this joint does not offer any special benefit to prevent the side from being pulled off, but this is not a concern in drawer construction.

Complex Lock Joints

Complex refers to the fact that they provide an additional dado on the front board that serves to resist the side panel from being pulled free.

Lock Miter Joint

Lock miter joints present the appearance of a mitered joint when viewed from the outside, but they offer the strength of a dado to resist separation.

Construction

Any of these joints can be made using a tablesaw with a dado blade and some patience, however the construction of any locking joint is greatly simplified by the use of a router table and an appropriate router bit. Once the router is setup and the bit height adjusted, one piece is passed over the bit while standing on its end grain against the fence, and the second board is passed over the bit while laying flat on the table. This will produce the two profiles that lock together.

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case

End Miter Case Joints

End miter joints, in its most basic form, are formed by mitering the ends of two boards at a 45ยบ angle, then butting the ends together. The disadvantage of this joint is that the glue is entirely on end grain (the weakest glue bond) and there is no form of interlocking between the boards. Basic miter joints are also notoriously difficult to clamp effectively, since the boards will always have a tendancy to shift against one-another.

Miter With Fasteners

The easiest way to strengthen an end miter is to drive nails or screws into each side of the joint, crossing directions to lock the joint together. Drilling pilot holes will help prevent splitting, and keeping the holes slightly towards the inside of the joint will reduce any damage to the face of the board should the joint fail and require repair.

Biscuited End Miter

Biscuits are small oval discs that are inserted into matching slots that are cut into the two boards to be joined. Choose a biscuit size that fits snugly into the slot, since any play will reduce the accuracy of the joint. Biscuits also provide positive registration for the matching boards, speeding the assembly and glue-up process. Just remember to keep the biscuit slots slightly towards the inside edge of the boards, to avoid weakening the exposed edge of the joint.

Splined End Miter

A spline is essentially a full-length biscuit. The slot is cut along the entire length of the joint on both boards, and a hardwood or hardboard spline is inserted during the glue-up process. The spline also provides positive registration which will help assembly, just like a biscuited joint, however a splined end miter joint suffers from a weakened outer corner since the wood at the corner is only connected by a thin strip once the spline has been cut. Because of this, it is essential that the slot for the spline be offset towards the inner corner of the joint.

End Miter With Spline Keys

This style of end miter joint is formed by creating a standard end miter joint, then cutting slots through the outside corner of the joint and gluing blocks or splines into the slots. Once the glue has set, the ends of the splines are trimmed flush with the ends of the joints. This has the advantage of adding strength to the joint, while giving it some visual appeal. Using a contrasting colour of wood gives the most dramatic effect. This joint can appear like a box joint, however the slots do not alternate on each side of the joint as the box joint would.

End Miter With Feather Keys

Using thin strips of wood instead of blocks gives the keys a more dellicate appearance. Restricting the slot width to the blade kerf makes this variation easy to make. The slots can also be easily made on any angle to increase the visual appeal, and will also add to the mechanical interlocking of the joint. The more keys that are used, the stronger the joint will become.

End Miter With Dovetail Keys

Instead of cutting the slots using a straight blade or bit, use a dovetail bit instead. This will produce a triangular shaped slot, into which you can insert a triangular shaped key which is then trimmed flush with the joint sides. This gives the visual effect of a dovetail joint on both sides of the joint. This variation also gives the joint some mechanical interlocking since the triangular keys prevent the joint from separating.