4 Quick & Easy Tablesaw Joints
For many of us, the tablesaw proves to be the cornerstone of building most projects. With this machine, you can rip and crosscut lumber to size, cut straight edges on boards that have none, and also cut many types of joinery. In this article, we show four joints you can easily create on your saw using a miter gauge and rip fence (and a few other accessories: See Sources, at end of article.)
For all of the joints in this article, always make test cuts in scrap stock to perfect the setups before machining your project parts. And in most cases, using a zero-clearance throat insert on your tablesaw will produce cleaner and safer cuts.
Best uses: any type of frame (picture, door, face frame)
A half-lap, shown above, consists of rabbets, dadoes, or grooves cut to half the thickness of mating workpieces. This joint lacks mechanical strength, but gets its strength from long-grain to long-grain bonding with glue. You can cut a half-lap joint in two ways on a tablesaw.
Using a single blade
You can cut half-laps best with a 40-tooth general-purpose or 50-tooth combination blade. This method cuts cleaner, smoother cheeks for stronger glue joints.
Using a dado set
Start by installing a stacked dado set; in most cases, the wider the better, because you can remove more material with each pass. Install an auxiliary fence on a miter gauge to combat tear-out where the blade exits the workpiece.
Tongue and groove
Best uses: edge-glued panels (tabletops, door panels, etc.), carcase backs, frame-and-panel doors
A well-made tongue-and-groove joint maximizes linear-edge glue surface while also providing goof-proof alignment of the mating workpieces. As with a half-lap, you can cut a tongue-and-groove joint with either a dado set or a single blade. In both cases, cut the groove first, and then cut the tongue to fit snugly.
Using a dado set
Install a stacked dado set equal to or slightly narrower than the width of the groove you want to cut. Be sure to use a zero-clearance insert—you'll need workpiece support on each side of the blade.
This hybrid tongue and groove is an open-and-shut case
Stub-tenon-and-groove joints find use primarily in doors and similar frame-and-panel construction in lieu of using cope-and-stick router bits. Cut this joint in the same manner as a regular tongue-and-groove joint, but with the tongue on the ends of a workpiece, usually the horizontal rails. Cut the groove first, sizing it to fit the door's panel. Then, size the tongue to fit the groove.
Using a single blade
Blade kerf (thickness) doesn't affect the quality of the cut, but thin-kerf blades might require more passes than a full-kerf blade.
Best uses: small boxes, drawers, chests, tool boxes
A box joint provides lots of glue surface for a strong joint. Use contrasting wood species to add pizzazz to its otherwise purely functional appearance.
You can use a stacked-dado set, but a dedicated box-joint blade set [Sources] yields cleaner, square-cornered cuts. Install the blade set to the desired finger width. You'll build a simple, inexpensive jig (explained in the coming steps) that attaches to a regular miter gauge. When machining the fingers, cut them slightly long so they'll be about 1⁄64 " proud when assembled. (Blade height should equal the workpiece thickness plus 1⁄64 ".) Then you can trim the joints flush when assembled.
When cutting box joints, separate the box sides into opposing pairs. For the purpose of this article, we'll refer to them as sides and front/back. Cut these pairs identically to create symmetrical joints.
To get started, cut a test side and a test front/back equal in thickness and width to the actual box parts. Then follow these steps to make the box-joint jig.
Rather than trying to cut boards to the precise width needed for a specific set of box joints, leave the boards a little wider than you think you'll need. You'll end up with a partial finger/notch on each, but you can quickly rip the boards to width before assembly.
Once you have a good fit, secure the plywood to the miter gauge with screws (or double-faced tape), cut both ends of the box sides in the first manner, then cut the front and back in the second manner. Glue the box together, clamp, and allow to dry. Trim the proud fingers with a block plane or flush-trim router bit.
Best uses: small boxes, picture/mirror/door frames
Miter joints look nice because they hide end grain, but they lack strength because glue doesn't bond well to the quartered end grain. Adding splines across a miter increases its strength substantially. (Cut spline slots with the blade at 90° as shown, or tilt the blade 5–7° for more pizzazz and strength.)
For perfectly square-cornered spline slots, use a rip blade, which has flat-tipped teeth. A blade with alternate-bevel tips will leave tiny "bat ears" in the corners that a spline won't fill.
To cut the slots, you'll need to build a rip-fence saddle jig, shown below, to cradle the mitered box. Your jig should slide back and forth easily on the fence but without side-to-side slop. But before tackling the splines, you'll need to build your mitered box and sand it smooth.
Add support with deep splines
For an integrated tray support in a splined-miter box, cut the center slots deep enough to penetrate the inside of the box at least 1⁄4 ". You'll need to make wider splines for this, but they will provide an almost-hidden built-in support.