Combine a live-edge slab and tempered glass to create a topographic top
A few years ago, my wife fell in love with a unique slab-topped table. What she loved most was the way the glass followed the grain of the wood. This clever combination resembled a topographic map of a river, while the live edge (flipped inward) seemed to rest just beneath the water’s surface. Unfortunately, the table had an equally impressive price tag. I’ve seen a few similarly designed dining tables sell for as much as $10,000.
Inspired by that design, I decided to build one for myself. Not too long after that, I began teaching others how to make their own one-of-a-kind tables at the Denver Woodcraft store.
What I like most about this project is that no two tables are ever alike. In this story, I’m building a 24 × 40" coffee table, but the size is up to you (and the slab you select). I’ve helped students employ the same techniques to make everything from small end tables to large dining tables. My largest project to date measures 33 × 50".
The project may appear difficult, but once the glass has been cut to the pattern (see “Clear Options,” below) most students can complete the top and base by the end of my 3-day class.
It all starts with a slab
Regardless of your table’s size, the order of work remains the same. The leg connection detail keeps the legs securely attached while allowing for normal expansion and contraction of each slab piece.
Order of Work
- Select and saw your slab
- Lay out the rabbet for the river’s edge
- Make a pattern and order the glass
- Rout the river bank
- Make the legs
- Finish and assemble
Unlike typical projects, providing dimensioned parts and exact step-by-step instruction doesn’t really work with this project. That’s because no two slabs are exactly alike. I think this creative freedom is part of the fun.
To build your table, first determine the desired dimensions, and then start shopping for a slab. To narrow the selection, start with slab thickness. My tables vary from 1-1/4"-to 1-3/4"-thick, depending on the size of the project.
Next, study the slab’s grain pattern and the shape of the its live edge (see “Slab Secrets,” opposite page). I favor boards with wild figure and bumpy live edges for more meandering streams, but straighter-grained slabs can be used to create more of a canyon look. Note that the grain determines the shape of the glass. You can create a wider table by using a wider glass panel, but forcing a wavy edge on a straight-grained board won’t look natural.
The width of the table will determine the width of the base, but you can modify the other dimensions. I typically use 4/4 stock for the legs, but for dining tables, I’ll use 8/4 stock, and mill just enough to flatten and remove mill marks.
To attach the leg assemblies to the top, I use connector bolts and threaded inserts. This pairing keeps the parts firmly connected, but permits the slab top to move in response to seasonal changes in humidity. As a final detail, I make a small rabbet around the top of the leg assemblies so that the top appears to float above the legs.
Slab Secrets
There are a couple of different ways to turn a live-edge slab into a river table. If the slab is wide enough, I’ll simply rip it in half and flip the outside edges inward. (If you can afford to sacrifice a little length, you can shift the halves to create better looking river bends.) For longer, narrow boards, I’ll crosscut, position the desired live edges in the center, rip the outer edges, and then trim both boards to length.
For large tabletops, you may need to use two slabs. In this case, it’s important that the boards are from the same tree; otherwise, the halves of your top may look very different when finished.
Until you’ve built a few tables, envisioning how the live edge will look can be difficult. I suggest taking a snapshot of the board and test-cutting a few printouts of the image before making sawdust.
Slice the top and set the stream
After deciding how to slice up your slab, use a track saw, or circular saw with a rip guide, to make your initial cut. Then, mill the boards to final thickness, joint the sawn edges, and cut the ends to length.
After milling, align the pair against a straightedge and set them apart to the desired width of the finished table. Make certain that the boards are parallel and square to each other. If they aren’t now, they won’t be once the table is assembled. Clamp them in place so that they can’t shift, sketch out your stream, and then make a tracing paper pattern.
To order your glass, you’ll need a rigid template.(For small tables, 1/4" hardboard is fine. For larger tables, I prefer 1/2" MDF because it’s stiffer and easier to handle.) To start, cut the panel to the length of your top, and a little wider than your river. To transfer the pencil lines onto the template, I flip the tracing paper over, insert a sheet of transfer paper, and run over my lines with a dull pencil. After rough cutting and sanding back to the lines on the template, check it against the layout lines, and then make a trip to your local glass supplier.
Rout your river
Because the cut glass often varies a little from the pattern, sand away the previous pencil marks and make a fresh set of lines. As before, make certain the ends of the top boards are square, and the edges parallel. Then clamp them to your bench.
Because most students aren’t used to freehand routing, rabbeting the top to fit the glass takes time, but it’s not difficult. Rabbeting involves setting the bit depth (aim for a hair more than the thickness of the glass) and then gradually working your way up to your line. A few tips can help, starting with the bit. To quickly rout the rabbet, I often use a 1/2"-dia. bit, but I suggest stepping down to a smaller 1/4"-dia. spiral bit for added control. To keep the router from tipping or veering over your lines, use a large offset base, and maintain a solid two-handed grip. Last but not least: take regular routing breaks. Hunching over a router can be exhausting.
Don’t expect the glass to fit perfectly on your first try. Simply mark the offending edges with a pencil, and cut them back with additional routing, or pare with a chisel.
Clear Options
The 1⁄4"-thick tempered glass used to make the table’s river section is too thick to cut in my shop, but any commercial glass company can do the job. I simply provide my supplier with the custom river template, on which I note my color selection and indicate that both ends should be cut 1⁄16" shorter than the pattern. This ensures that the glass will not be longer than your top.
Choosing the perfect color can be challenging. (I compared 50 different shades of blue before finding my favorite.) A few of my other favorite shades are shown below. The color you select depends on not only preference and availability, but also on the wood. As a rule of thumb: the darker the wood, the lighter the glass. You don’t want to hide your rabbeted river bank.
In order to find the best pairing, I suggest finishing a scrap cut from your slab and bringing it to the glass shop. If you plan to make multiple tables, ask your supplier for glass samples.
Mortise the legs
As shown in the main figure on page 36, the connector bolts are concealed in counterbored slots in the rails. To rout this slot I often cobble up a simple jig like the one shown above. Using a 1" bushing and 3/4"-dia. straight bit, rout a 1/4"-deep groove to hide the bolt heads. Next, replace the bit with a 3/8" spiral bit, and rout the through grooves. If your boards are narrower at one or both ends, shorten the slots so that they don’t show through the glass.
To join the legs to the rails, you can simply use dowels or rout for loose tenons. Alternatively, you can show off your joinery skills with dovetails or finger joints. For the sake of my class, it’s hard to beat the speed and convenience of the Festool Domino. Following assembly, rout or saw a 1/4 × 1/4" rabbet around the top edges and ends of the rail/leg assemblies.
To locate the holes for the threaded inserts, clamp the leg assemblies flush with the ends of the top boards and set the glass in place. Working underneath the table, make two marks about 3/8" in from the ends of the slots. Next, drill the holes into the top, and drive in the inserts. To prevent damaging the inserts, I often drill oversized holes and set the inserts in epoxy.
Your table’s almost done. I don’t think that highly-figured wood needs a fancy finish to look good. After sanding the parts up to 320 grit, I wiped on a coat of natural Danish oil to enhance the color of the wood. After giving the oil time to cure (a week is good), I applied four coats of General Finishes HP waterbase polyurethane with a HVLP sprayer. The finish needs a few weeks to fully cure, but you can reassemble the parts and put your table to light use within a day or two.
