Make a Slab-Topped Coffee Table

This live-edge coffee table is just the beginning of what you can build with a $20 doweling jig.

Project #2302 • Skill Level: Beginner • Time: 4 Days • Cost: $400

This walnut coffee table is featured in my latest book, “Build More Stuff with Wood,” (see all the places you can purchase it here) the second in my series for beginning and intermediate woodworkers. It’s part of a chapter centered on an amazing $20 doweling jig you can use to build a houseful of strong furniture. In this excerpt from the book, I’m using it to build a clean, strong base for a natural-edged walnut slab.

Slabs are popular for all sorts of tables and counter tops, so I’ll share a great way to flatten and smooth them with a little help from your local mill-work shop, and refine their edges using basic tools and techniques. Natural-edged slabs are unique objects, so you are unlikely to find one that’s the exact same width and thickness as the one featured here. And that’s fine. Use anything in the general ballpark, in any sort of wood, and adjust the size of the base to suit it. You can also glue together a series of boards to make a rectangular top for this table.

The techniques are the most important part of this project. Before I found this simple jig, I wasn’t the biggest fan of dowel joinery. Once I gave it a try and realized how versatile and effective it is, I started dreaming up all sorts of furniture to make with it.

Cutlist and Diagrams

Simple & Versatile Doweling Jig

This jig is made by Powertec and sold on Amazon. I’m going with the 3/8“ size here, which I find to be the most versatile. Due to the size of the dowels and the maximum depth of the holes you can drill with a 3/8“ diameter drill bit, this version of the jig is appropriate for small- to medium-sized furniture like this coffee table. If you buy the jig designed for 1/2“ diameter dowels, however, you can make everything up to the largest dining tables and the biggest beds.

1 Simple, strong, and affordable. Available for about $20, this simple doweling jig will deliver a wide array of joints. It includes 3/8″ bit and a stop collar used to set drilling depth.

The jig is really nothing more than a block of metal that guides a 3/8“ diameter drill bit, with a tough, clear plastic fence attached. The fence locates the jig on a workpiece and provides a surface for clamping it solidly in place. The kit also includes drill bits, along with a stop collar that controls drilling depth.

2 Replace the standard bit. The kit comes with a standard twist drill (pictured on the right). These cut roughly in wood, so replace yours with a high-quality brad-point bit (shown on the left). It will cut quicker, smoother, and cleaner, and make more accurate holes.

Despite its simple design, or maybe because of it, the jig is extremely versatile. Used in the most basic way, it lets you drill two clean, 3/8“ holes, spaced 3/4“ apart, which then accept two 3/8“ dowels. Drill those in two mating pieces, squirt some glue in the holes, tap in the dowels, clamp the parts together, and they are joined for life. The basic ability lets you join parts at 90° for all sorts of projects, from doors and picture frames to the base of a table. It also joins boards side by side to create strong panels and tabletops, aligning the pieces at the same time.

3 Set the stop to drill 1/8″ deeper than necessary, to give excess glue a place to go and make sure the joint will close completely. To set the depth for most joints, draw a line halfway along the dowel you’re using, and make sure the bit passes the line by a little before locking the stop collar.

4 Mark a line across the joint. This can be centered by eye.

5 Clamp the jig firmly onto the workpiece, with its centerline aligned with the mark on the workpiece. Place the drill bit in each hole before squeezing the trigger, and drill until the stop-collar hits the jig. It helps to pull the bit partway out of the hole at least once as you drill to clear chips.

6 Choose good dowels. The best type of dowel (on left) is sold specifically for joinery and tends to be very accurate, with spiral grooves that allow glue and air to escape when you drive them in. The middle type is also sold for doweling but doesn’t create quite as strong a bond. On the right is a dowel cut from long hardware-store dowels. These tend to vary too much in size. Whichever type you use, make sure they fit well in the holes your drill bit makes.

7 Assembly is quick and easy. Squirt some woodworking glue into the holes and use a small stick or brush to spread it evenly. Then tap in your dowels. You don’t need to apply glue to them. Then spread glue in the other pair of holes and push the parts together. Add clamps to produce a strong, tight joint.

I’ve been using this jig with students for a few years now, and I have a number of tips to share:

1. You should replace the standard 3/8“ drill bit with a 3/8“ brad-point bit, which you can buy for less than $10 on Amazon. The brad-point bit will create a more accurate hole with a cleaner entry rim, and also make drilling faster and easier.

2. To attach the jig solidly to the workpieces, avoid spring clamps and Quick Grip-style clamps, which won’t hold tightly enough. Go with the clamps that ratchet or screw down solidly.

3. As for the dowels themselves, you could cut up the long dowel rods sold at home centers and hardware stores, but I find that these vary too much in diameter for effective joinery. Instead, I recommend the precut pins made for dowel joinery in various sizes and lengths. These not only offer a consistent fit, but also have little slots on their sides to let glue and air escape when you tap them in their holes.

4. Last, if you happen to drill a dowel hole or two in the wrong spot, glue a dowel into the hole, let it dry, saw and sand it flush, and then re-drill in the right spot. If it’s an obvious spot, you can use a dowel cutter to make a matching dowel from your project wood.

8 Offset joints are easy too. If you place a thin piece of plywood or MDF between the guide block and the plastic fence, you can offset the holes by any amount. You’ll need slightly longer screws to attach the fence.

9 To create joints with more than two dowel holes, place a dowel in the last hole you drilled, and place the jig on that dowel to line up the next hole.

How to Handle Big Slabs

The size of the slab will determine the size of the base, so get the slab first. Check your local area for slab suppliers and look for deals on Craigslist. Avoid slabs with big cracks or deep defects. There’s a few things to note before you go find your ideal slab. Wide, thick wood slabs have enduring appeal. Rustic yet refined, they tell the story of the tree, especially if the edges of the log are left intact. But these big slabs can be tricky to handle. For a start, they tend to warp as they dry, and flattening them is beyond the capacity of common woodworking machines. There are huge router jigs you can make to flatten them, but those are hard to justify if you use slabs only once in a long while. Handplaning also works, but it’s tricky to flatten a big slab by hand, making that approach best for hand-tool users with a fair amount of experience.

10 Mark a square line across both ends and use a circular saw and saw guide to trim the thick slab to size.

11 Rent time on a wide-belt sander. Many large mill-work shops rent out time on their big, wide-belt sanding machine at a reasonable rate and provide a skilled staff member to guide the process. It cost me $60 to get this slab smooth and flat.

That’s why many woodworkers take their slabs to a local woodworking shop with a wide-belt sander—a big, expensive machine designed for tasks just like this. For less than $100, a pro will run your slab (or slabs) through the sander on both sides until it is dead-flat or smooth, leaving you just a little bit more sanding to do with finer grits before it’s ready for a nice finish. Nowadays I also belong to a local woodworking club with the same type of machine, which lets me flatten big slabs for just a few dollars-worth of shop time. Using a wide-belt sander saves a lot of time and frustration, leaving you more time and energy to devote to the rest of the project.

Lastly, reshape the natural edges if they are damaged or unattractive.

12 Strip off any bark first, as it will only pop off over time. If the edges are damaged or acutely angled, reshape them as follows. Draw a line along one of the grain lines, set a jigsaw to a nice angle, and follow the line with the saw.

13 Sand away the saw marks and the smooth, curvy new edge will look just like the real thing, only better.

Drill the Dowel Joints

Follow the photos carefully to understand how the jig is aligned to create the two different arrays of dowels.

14 Mill and mark the frame pieces. After ripping square parts from 13/8″ thick board, line them up so they look their best and mark across the joints to record their orientation. A white pencil works great on walnut.

15 Drill the posts. Mark the outside face of each post with an arrow to be sure you drill on the inside face. Line up the jig with the end of the post as you position it on each side.

16 Drill the rails. The jig is positioned the same way—on two opposite faces of the workpiece—to drill into the ends of these pieces. Make sure you are lining up the end of the jig with the outer face of the rail each time, so the rails and posts end up flush at the corners.

17 Mark centerlines for the slat joinery. The three dowel holes are centered on the slats, so we’ll work from a centerline this time. Mark centerlines on the end of the slats and the outside faces of the rail and posts.

18 Slat joinery is a little different. Start by drilling the ends of the slats. Line up one of the holes with your centerline and drill it and its neighbor. Then drop a dowel into the center hole and use it to position the jig for drilling the hole on the other side of the line. Before drilling the corresponding holes in the sides of the frame parts, add a 1/4-in. MDF spacer to the dowel jig, as shown earlier.

Assembly & Finishing

The table goes together squarely and solidly due to the use of dowel joints. Other than their speed and simplicity, one of the other things I like about dowel joints is how easy they are to assemble. Before assembly, however, sand all of the base parts to 150-grit, and then do little more sanding afterwards. Next, make sure the dowels you are using fit the holes your drill bit is drilling. You’re looking for an easy but not loose fit, as the glue will tend to swell the dowels a bit. You can sand dowels a little, but if they are very tight, it’s probably best to try another type. In case the joints get a little rebellious once glue is applied to the dowels, have a few long clamps ready to draw the parts together. This works much better than hammering on them with a mallet.

19 Assemble the frames first. Start with a dry-fit to make sure everything comes together okay, before spreading glue in the holes, tapping in the dowels, and assembling the frames.

20 Add the slats. Use clamps to draw these joints together tightly. Before attaching the top, finish sanding the parts and apply a tough finish. I used oil-based polyurethane.

21 Attaching the top is easy. Long screws pass through the frame parts to hold the thick slab securely.

Once the base is assembled, finish the base and the top separately before screwing them together.  Coffee tables need a tough finish, so I brushed Minwax’s oil-based polyurethane onto the top. The base doesn’t need as much protection, so I used a few coats of Minwax Wipe-On Poly for that. I used the satin version of both, which gives a soft sheen. Be sure to stir the containers well each time you apply finish, and vacuum away the dust every time you sand, especially between coats. If you can feel a little dust in the final surface, you can rub it with a brown paper bag to give it a buttery feel.