With the four other sides of the box veneered and trimmed flush, the top is ready for glue-up. Shown here is the box, prepped for the vacuum bag, with a large panel on top to distribute the clamping pressure evenly.

Once all five sides are veneered, the box is ready for final sanding. Since the veneer is so thin, I prefer to sand each surface by hand, rather than with a sander. This gives me greater control, and decreases the chance of sanding through the veneer. (Sanding through = start the project over. While you can never really have a truly bad day at the shop, this would be about as close as you could get.)

Sanding a very small chamfer on the edges of the box. This should give the piece a slightly softer “feel.”

Burnishing the edges. This will further round over the edges, but will do so by compressing the fibers of the wood, rather than actually removing more material. Burnishing will also help prevent the edges of the veneer from catching on something and pulling up.

The completed box, ready for finishing.

In this flattering picture, I am masking off the edges of the veneered end pieces. This way, if there is any glue squeezed out from the next round of veneering, I can simply peel it off, rather than sanding and scraping.

Preparing the box for the vacuum bag. This was a tricky glue-up, since both the top and bottom of the box had to be glued up in one shot, and the entire thing had to somehow fit into the bag. Glue-up is usually a good exercise in emergency preparation and disaster management. Crossed fingers help, too.

Mantel Box, post-glue up.

I cut each piece of veneer about 1/8″ oversize in each direction. Too much overhang, and the veneer will snap off inside the vacuum bag; too little, and you run the risk of the veneer stopping short of the end of the piece. This would officially qualify as a “disaster.”

Trimming up the edges with a flush-trim bit. The masking tape also prevents the bit from scraping off the delicate layer of veneer.

Now that the box itself is glued up, the next step is to veneer the outside. To create a “seamless” look for the box, I am going to lay on the veneer in a very particular sequence: first the ends, then the long sides, then the top. Before I can do that, however, I need to make sure the end pieces are completely flush across their widths. Since the veneer is so thin, any discrepancy in the substrate will translate through to the surface. In this picture I am sanding the edges of the long pieces flush with the end pieces.

Sealing the edges with watered-down yellow glue. Sealing the edges will help with glue adhesion, and should prevent the veneer from peeling up around the edges later down the road.

Because the ends of the box have both end grain and face grain, I am using poplar veneer as a backer underneath the Birds’ Eye Maple. The backer will also even out any remaining discrepancies in the surface of the MDF.

Gluing up the ends. In this case I used eight pipe clamps, four pairs of bowed cauls, and two MDF “pads” to ensure even clamping pressure.

Once the backer veneer is glued up, the Birds Eye Maple is laid on and glued up.

Trimming the veneer flush with the edges. Once the edges are completely flush, I can overhang the veneer for the other three sides of the box. Don’t worry, I swear this will all make sense in the end…

The first step after pressing up the panels is to trim the veneer down with a knife in preparation for trimming the panels flush using a router bit. I try to leave about 1/16″ overhang on each edge. This will prevent the thin, overhanging veneer from “flapping” against the router bit, which is hazardous both to the operator, and more importantly, the piece.

Trimming the panels with a top-bearing flush-trim bit. This is where using just the right amount of glue pays off - since there is almost no squeeze out, you can use the original panel edge as a bearing surface, rather than planing a new edge by hand.

Cutting the miters on the long edges of the panels. I use an 80-tooth blade made especially for cutting veneered panels. I’d highly recommend one if you do any sort of veneer work - the make accurate cuts, and leave a tearout-free edge.

Ripping the panels down to exact width.

All five sides of the box, laid out and ready for finishing. The three long sides will be joined with miters, and the two smaller end pieces will be attached with butt joints.

Pre-finishing the insides of the box with shellac. Whenever possible, I prefer to finish a piece before it is glued up. This way I have greater access to each surface, and ultimately greater control over the final finish, as there are no nooks or crannies for finish to hide in.

Sealing the edges of the MDF. Because the edges of MDF are so porous, any glue that is applied is sucked up like a sponge. For this reason, I am applying two coats of glue (in this case, extra-slow setting West System epoxy): one coat as a sealer, the second as the actual adhesive.

Gluing up. The trick is to apply even pressure, but not over-tighten the clamps, as this could cause the joints to blow-out.

Checking for square during glue-up.

Assembled Mantel. Next up: Veneering the outside of the box…

This project calls for a large (55″ wide x 12″ tall x 7″ deep) box made from Birds’ Eye Maple to serve as a Mantel piece over a fireplace. Due to construction and installation concerns, we decided that the best way to go about the piece would be to veneer the entire thing. Using MDF as a substrate under the veneer means that the piece will be absolutely stable - in other words, no wood movement to worry about. In this case, the piece will be constructed from one sheet of 3/4″ MDF, and veneered on both the inside and outside of the box.

The first step is to rip the 8′x4′ sheet into manageable strips. As with any project, I like to cut each part oversize, then come back later and trim them down to final length and width before assembly. In this case, I cut each part (the front, top and bottom, and two sides) about an inch longer in each direction.

With the MDF cut, I cut each sheet of veneer about 1/4″ longer and wider than the substrate. This allows some play if the veneer happens to shift during glue-up.

I prefer to cut veneer with a knife and scissors, rather than a veneer saw. I find it much faster, and because I don’t need to join the sheets along a seam, the edge quality is not of utmost importance. Besides, everything is going to get trimmed down to correct size later, anyway.

The next step is to make the platens, which ensure even clamping pressure once the veneer/MDF “sandwich” goes into the vacuum bag. In this picture I am rounding over the edge of one of the patens. This will keep the vacuum bag from tearing once the pump is turned on.

Filing down the corners of one of the platens, again to keep the bag from tearing.

Glue-up, using Unibond-800 (a kind of urea-formaldehyde glue) and a cheap foam roller. At Darryl Keil’s advice, I decided to veneer to one side of each piece of the box at a time. Once the poplar “backing” veneer is applied and pressed, the sides will be cut to correct size, and the box will be constructed and glued with the poplar veneer facing the inside of the box. The Birds’-Eye Maple veneer will then be applied to the outside of the box, one side at a time.

The vacuum bag, which works by sucking all the air out of the vinyl envelope-style bag, exerts an enormous amount of pressure on the parts inside. A common misconception is that the bag is “pulling” down on the the parts. This is not so. Rather, the lack of air within the bag (the vacuum) allows the atmosphere itself to “press down” on the bag. That may not seem like much, but there is actually over 2,000 pounds of pressure per square foot being applied to the bag. If you look closely you can see the bag stretching over the platens on top of each stack.