Because you’re attaching wood fibres at their porous ends instead of along their sides, any junction that logs end grain to end grain will be below. (Imagine glueing two drinking straws together at the ends rather than along the sides.) For those rare occasions when end-to-end joints are required, such as connecting two pieces of crown moulding on a long wall or making the most of elements that are too short for your project but too lengthy to waste, you can reinforce them.
When it comes down to it, you either need to add reinforcements like plates, dowels, or screws, or you need to cut the joint to produce mechanical strength and expose more face or edge grain for a stronger connection, like the finger-joint joint shown above. Check out these eight options, which range from simple to elegant.
Straps that are simple and functional
Simple metal or plywood straps can reinforce butt joints where they can be hidden or when beauty isn’t a concern, such as on the backside of a wide crown moulding where waste isn’t an option. Making your custom-sized straps out of 14″ plywood saves money while providing a solid bonding surface.
Cut a hardwood strap as wide as the workpiece will allow it to be installed. When attaching elements having a profile on the opposite face, such as moulding, place the screw holes over the thickest profile points—for example, at the peak of a ridge or curve.
One side of the strap should be glued and screwed to a workpiece to form the joint. After the glue has dried, glue the second half of the belt to a flat surface and fasten the assembly. Raise the other workpiece roughly 14″ at 3′ from the jointed end for a tight joint. Then, as illustrated below, push the components together while installing the mounting screws. Before handling the junction, lay both pieces flat and let the glue cure.
Screws with a pocket hole
Another quick way to fix butt joints is to use this procedure. Drill an angled hole through 1 workpiece and another with a pocket-hole jig to install pocket-hole screws. As demonstrated below, a screw put into the hole brings the components together. Workpieces should be at least 12 ” thick (with 1″ screws), and portions 112 ” or thicker should be attached with 258 ” screws. Find out more about pocket-hole joinery.
Splines provide inner strength.
Splines form a flex-resistant face-to-face adhesive surface. For a simple connection with visible splines, use through splines. Set the saw blade 34″ high?—half the length of the splines—and mark each joint on its top face. For consistent groove placements between parts, align the top sides of each piece against your rip fence. Add an auxiliary fence to keep extra-long parts stable. Cut kerfs on the ends of your stock to produce a groove as wide as one-third the thickness of your inventory, using a backer block to prevent tear-out.
After that, the plane saw the blank spline stock to fit the groove width and depth. Splines can be made from plywood or solid timber. If you use solid stock, align the spline grain with the grain of the workpiece, as shown below. After inserting the spline, glue and clamp the pieces together.
Like the one shown below, create a hidden spline that disappears when the joint is assembled with little extra effort. We used a table-mounted router and a 14″ straight bit to make this junction. Set the bit height to just over half of the splines’ width. Then set the router table fence so that the bit is centred on the thickness of the workpiece ends.
Then, to guide your workpieces, construct a basic jig. Cut two stop blocks from scrap that are somewhat thicker than your workpieces. They should be spaced by double the width of your workpiece, minus mortise insets on both sides. Then, for enhanced safety and control, install a crosspiece that is 12″ broader than the bit height. Clamp the final jig’s connected stop blocks to the router table fence equal distances from the bit, as shown below. Mark the high faces of your workpieces and face them while routing the slots to prevent slight fence adjustment errors from causing an uneven connection. Push the workpiece against the router fence and down the right stop block’s edge to the router table with a push pad. Slide the workpiece to the left end block and raise it clear of the bit.
Dowel and drill
Another inconspicuous connection is provided by a dowel joint, as seen below. Mark the dowel positions on both sides of the parts to be linked. Drill holes 1/16″ deeper than 50% the dowel length with a doweling jig over the marks. Spread glue in the gaps of one section, insert the dowels and clamp it to a level surface. Glue the end grain and holes on the other piece, press the parts together, and clamp until dry.
Scarf joints with a bevel cut
You can expose more long-grain for a better connection by cutting the ends at an angle before connecting them. The greater and better the bonding surface, the steeper the curve. A 45° angle, for example, increases the glueing area by around 40% and hides the joint line on a contoured surface. Cut one end of the saw blade on one side and the other on the opposite side to match the angles, as indicated below. The components will match even if your blade bevel angle is lower than 45°.
Clamp the lower half against a flat surface to unite the two halves. The upper piece should then be clamped against the lower piece’s bevel. If required, use a straightedge to align the parts.
Scarf joints with a mitre cut
For a larger glueing surface, try this joint. Make a 4:1 angle guide that is more than twice the width of the workpieces to start. (For a 2″-wide workpiece, use the 5×20″ guide shown in the photographs.) As demonstrated below, identical cleats on both sides of the triangle aid in positioning it on the face of both workpieces. Both workpieces should have angles marked on them, and they should be bandsawn to within 1/16″ of the waste sidelines.
After that, insert a straight bit into your router. Clamp the guide and workpiece together, with the workpiece edge overhanging, against the top of a sturdy surface, such as your workbench. To help stable the router base and back your cut at the tip, place the triangular scrap terminated by the bandsaw beneath the angled guide and adjacent to the narrow information, as illustrated below. Then trim the leftover waste to the line you’ve drawn. Rout the other workpiece by flipping the guide over.
To put the joint together, glue the mitred edges together and loosely hold them together so that both edges form straight lines. Then clamp both parts on a flat surface to keep them from slipping when you join them.
Half-lap joints are the most basic.
Half-lap joints generate face-to-face bonding surfaces and are attractive, sturdy, and simple to construct on a table saw or router table. The stronger the link, the more overlap there is.
Begin by marking your cuts for a simple half-lap joint. Keep both workpieces side by side with the ends flush, and the look side up on one and down on the other for identical laps. On each piece, draw an “X” where you’ll cut your lap; then draw a line across both parts, extending the lines from the faces to the edges.
Next, in your table saw, add a dado set that is at least 5/8″ wide and fix the blade height to cut half the thickness of your workpieces. As demonstrated here, scrap is used to test the joint’s fit. The test scraps’ faces should be flush, and the laps should have strong wood-to-wood contact.
As illustrated below, cut a dado from the specified joint lines to the ends. A mitre-gauge extension aids in the positioning of each pass while also reducing tear-out.
Then, as illustrated below, the test fit the joint, looking for space between the laps or between the bench and one of the faces. For a permanent connection, glue and fasten the laps together.
Lap joints that are tabled
This joint combines the strength of linking pieces with a half-lap joint’s huge glue surface. To make it, increase the width of the workpiece by 14″. (You’ll take it out later while fine-tuning the joint.) Then measure from the workpiece’s end. As with a normal half-lap junction, mark both pieces simultaneously. Make a pair of test pieces the same thickness as your final workpieces and duplicate these markings.
Fix the blade height to exactly one-third the thickness of your workpieces, using the same dado set up as for the standard half-lap. Then, from your edge lines to the ends, rabbet both components and the two test pieces.
Reset the height of your dado blade to two-thirds the thickness of the workpieces. Test and modify the dado depth with scrap pieces until the thicker segment at the end lies within the narrower section and the faces of both pieces are flush.
Place a mark from the shoulder of the dado to a distance equal to one-half the width of the workpiece. Make two passes with both parts clamped to the mitre gauge to determine the width of the second pair of dadoes, as shown below. Cut the remaining dadoes after that.
Trim the ends of every piece separately until they fit the deeper dadoes, as illustrated below, to guarantee a tight union. Then glue and clamp the pieces together to create a joint that demonstrates how to stretch aboard in style.
