Intro: Glass Top Shadowbox Coffee Table
I was asked to make a coffee table by a friend, and she gave me creative license to do what I wanted with the design. The only thing she asked was that it fit a particular width and length so that it would fit nicely in the area she has in front of her couch. I got to work making a couple of sketches, then on to some scaled drawings with a couple of different layouts. She chose the design above with the boards at a 30 degree angle off the center line, and then I got to work. I wanted the table to be a bit of a surprise, so I didn't show her anything else until I delivered the finished product. Most of the pictures for this were taken in my garage, so please excuse the random backgrounds.
1" X 4" clear pine
1" x 8" clear pine
1/2" X 3" clear pine
3/8" x 3" clear pine
1" square steel tubing
1" flat stock steel
Small piece of sheet metal
16" handy panel
Black, high gloss, automotive spray paint
1/4" tempered glass
Drill and bits
Step 1: Cutting the Substrate and Shadow Box
Once I had my scaled drawing adjusted for the true thicknesses of the material I'd be using (e.g. 1" x 4" clear pine measures 3/4" x 3-1/2" finished, etc.), I figured up the total amount of material I would need to build the surface of the table, plus about 10% just in case. I bought 1/2" clear pine for the border of the table, 3/8" for the walls of the shadow box, and (I believe) 1" x 8" clear for the base of the shadow box.
Cutting the plywood substrate to shape was the first step. Easy enough to do with a relatively steady hand and a circular saw. Next came the layout of the shadow box. The dilemma was deciding how deep to make it, but also how long/wide to have the finished interior space. As I thought about it, I realized that the box would be far stronger (and simpler to construct) if I attached the walls to the outside of the base. A few quick cuts on the miter saw had my pieces ready to be assembled for the box. I glued and nailed the sides and ends to the base on a nice flat surface to keep the top edge all on the same plane. I then used the outside dimensions to determine my cut for the opening in the plywood. I measured and marked where the box was going to sit, drilled holes near the inside corners, then cut the opening with my jigsaw. After that was done, I attached the first two surface boards so that I would have a reference point for everything moving forward. Then the first challenge popped up!
I wanted the top edge of the box to sit flush with the finished surface of the table, so I knew I needed to account for that 3/4" difference. The big challenge was deciding how to mount the box to the substrate. I could have done it by measurement, but I wanted to be absolutely certain about where I was going to be drilling holes, so I clamped a piece of 1"x material to each edge of the box, put the substrate on blocks to raise it, then set the box in the hole. I then marked the edge of the opening on the outside ends of the box and had my line to mark for my nails. I tried to simply rest the substrate on some of the 1"x material and invert everything, but there was a slight bow to the plywood that made me nervous. Over-engineered and overthought? Probably. Successful? Yep! I attached a small nailing block to each end and nailed the assembly to the substrate. On to the surface boards!
Step 2: Surface Boards and Why You Should Only Use One Saw!
With the shadow box attachment figured out, I thought it would be relatively smooth sailing until I got to the welding (I'm not an expert welder). I was right...until I was wrong! You've heard the old saying, "measure twice, cut once," right? Right. We all have. Well, what they don't tell you is to measure twice and cut once on only one saw! I started the project at my house, but found myself in need of my dad's table saw in order make all the edges nice and clean when the assembly was complete.
I wasn't quite finished with cutting all of the angled boards for the surface, but I took all of my materials with me so I could make good progress the night I was there. I grabbed the miter saw, took some measurements, and started cutting. There were gaps. As it turns out, my dad's miter saw and mine were slightly off at 30 degrees, which meant that the pieces didn't butt together the way they needed. There was some creative language that ensued, but it just meant I was going to have to use a little more putty at the end. It's important to note that I didn't realize this was the problem initially, so I tried to trim the board that didn't fit perfectly with the result that I made a few of the boards a little too short. Remember that 10% I mentioned at the beginning? I used that and more trying to fix my mistakes. So, what did we learn? Make sure that whatever saw (or saws) you use is properly zeroed before you start trying to make nice, tight joints.
Aside from the saw issue, things went together pretty smoothly. For the trickier cuts where the surface boards met the corners of the shadow box, I used the band saw. Measuring them can be a bit of a challenge, but if you butt the board to the point of the corner, you can measure the negative space between the boards which will give you the width and depth of the cutout. It's a little hard to put into words, and I'm sorry I don't have a picture of it, but that's the best I can describe it. Almost all of those joints came out really well, so after a few more small cuts for the corner and center end pieces, it was ready to be glued and nailed together.
I spread glue over the substrate plywood, then laid my surface boards down one by one, keeping them together as tight as possible. I used a couple of brads in each board to keep it in place while I added the rest of the surface boards. Once everything was attached (except for the little triangular pieces on the ends) I flipped the top over, liberally added more brads, then weighted everything down to ensure a nice solid top. After the glue had a day to cure, I flipped it back over and glued/nailed/clamped the remaining small pieces in to finish out the top. A few small passes over the table saw guaranteed the edges were smooth, and phase one of the woodworking was complete!
Step 3: Laying Out and Welding the Frame
I haven't done a lot of welding in my life, but I've always been envious of those who can do it well. You have to practice, so this was my chance. My plan called for me to make two U-shaped legs and join them with an X-shaped brace. I thought I could pretty easily attach a mounting plate to the ends of the legs in order to screw them to the top. No real troubles with any of that part!
I marked and cut the tubing on a 45 degree angle with my hacksaw, but the sheet metal I cut with my reciprocating saw. If you're counting, that's the sixth different saw used in this project! Once all of the cuts were made it was time to try my hand at tacking them together. If you're not an expert welder, and you're trying to make good square joints, invest the $6-8 dollars in a welding magnet! It made my life immeasurably easier than I thought, and I've used it on other projects (including another coffee table project I wrote about here).
I used the magnet to position the pieces to be tacked together, gave each one a small tap with the welder, and inspected my handiwork. Not bad! Since that went well, I welded up the first frame with decent results. I had a couple of holes in the weld, which were a result of the temperature and feed speed suggested on the welder being a little too aggressive for the material I was using. Fortunately, you can add more material by carefully welding, so I filled the holes and went on. The quality of my welds steadily improved throughout the process, and everything was strong and square by the end. A grinder makes quick work of cleaning up the welds, but don't get too aggressive or you'll end up with deep scratches in the metal.
The X-shaped brace started as a bit of a challenge, but turned out to be easier than anticipated. I knew what the overall dimensions needed to be, so I cut the two pieces to length, laid them across the tops of the legs, marked the joint top and bottom, then welded them together. Once that was done, I put the assembly back on top and marked what needed to be cut out to weld them inside the leg positions. Some trimming here and there with the hacksaw got me dialed in. I attached the mounting plates to give the legs some stability, then flipped them upside down, positioned the cross brace, and tacked it in place as well. Success!! Everything was square and level, so the welding portion was now finished.
Step 4: Starting the Finishing
Short step here. Once I had the welding finished, I was getting close to completing the project. I puttied all the joints and nail holes in the visible portion of the top. As you can see, I was a bit liberal with it, but I wanted it to look as much like a solid surface as I could. While waiting for the putty to cure, I wet-sanded the metal frame (better be ready to get dirty!) with 300-400 grit sandpaper to make sure the surface was nice and smooth. Once I'd dried all of that off, I sprayed the frame with 3-4 light coats of gloss automotive spray paint to keep it from running, and to keep it durable (kid-proof).
After the putty had dried, I sanded the top. I started with 80 grit to take off the excess putty, but since these boards were clear I could quickly move to 120. I used a pad sander for a large portion of it, but since this would be stained, I had to be very careful not to sand the grain on the other half of the top the wrong direction. I went over everything with 150 grit by hand to finish it off.
Step 5: The Final Woodworking Steps
Just prior to the sanding, I cut the outer trim pieces for the top from the 1/2"x3" clean pine. I 45'ed the corners to make the joints nice and clean, then I sanded all of that along with the remainder of the top. After I had finished welding the frame, I measured and cut the handipanel I'd bought for the shelf (I didn't have my Kreg jig or a biscuit joiner for this project). I notched out the corners, got a good, snug fit, then drilled holes in the cross brace where I would attached the shelf. This piece, too, got sanded with everything else.
I carefully nailed the trim board to the top, leaving a little shy of a 1/4" lip around the surface of the top. This would border the glass top that would cover everything. A little more putty to cover the nail heads and fill the corners just a little more, then it was ready for a final sand and a test fit. When it all went together well, I pulled it back apart and stained the wood. I let that dry, then put on three coats of satin polyurethane.
Step 6: The Finished Product!
When everything was good and dry, final assembly began. I was careful not to scratch the paint on the metal, nor damage the finished wood. Turns out that left over styrofoam packing blocks worked perfectly to support the shelf when I screwed it on.
I put a blanket down, turned the top upside down, and set the leg assembly on to attach it. I must have measured my distances from the legs to the corners 50 times before I was sure I was in the right spot, but everything came out right where I wanted it in the end!
The glass I got was custom-sized, tempered glass that I ordered from a local glass company. Since this is intended to be a high-use item, I don't want someone to accidentally drop something on it and shatter it. I had hoped to come up with some sort of creative system to be able to remove the glass, but my friend needed the table a little sooner than originally expected, so I had to forego that idea.
Here ends my Instructable! I'm happy to say that it's been in use for more than 18 months in a house that includes a boy under 4, and no issues have arisen. Thanks for reading, and I hope you enjoyed!