Intersecting Box Shelf

An intersecting box shelf is a simple but elegant way to display items in your home or business. As many other projects the ability to customize it makes it very appealing. I worked with the client who commissioned the project on the design, joinery, and wood selection. We decided to use Sapele as the primary wood with Walnut splines in the miter joints. It’s important to keep in mind the location that the project is going. In this case the client had a specific wall that it would be hung on so available space and other features like matching the angle of the cathedral ceilings were important. As with most of my projects the first thing I did was to draw in up in SketchUp to get the dimensions and proportions down.

The lumber was purchased from Steve Wall Lumber in Mayodan, NC. It is about a two and a half hour drive for me but I haven’t found anywhere closer that has the quality and prices that they have. I only charge customers for the lumber used in a project but always estimate on the high side when purchasing. This way I won’t have to make another long trip if I mess up a part. Once I got the lumber back to my shop I let it acclimate for about a week before starting to mill it up.

Since I am using rough cut lumber for this project I will have to mill it down and then cut it to its final dimensions. A common mistake that I have done way to often is to get exciting about making saw dust and cut it down to much. Since I can’t afford a board stretcher I need to plan ahead and take a few precautions. The first thing I do is to mark each of the parts out to a rough dimension on the boards with chalk. I use chalk since it is easier to see than pencil and we don’t need exact lines here. Since both boxes that will go into this shelf are the same dimensions I’ll have eight identical parts.

 Since I have a six inch jointer in my shop I need to rip the boards to 6 inches wide on the table saw. Again we are just worrying about getting them to their rough dimensions right now.

Once the boards are ripped down I take them over to the miter saw and cut them down to rough length. Since the final length of each box is going to be twenty-one inches I cut the parts to twenty-three inches.

From there I take the material over to the jointer where I will joint one face and one edge of each board. If you purchase your lumber S4S (Smooth 4 Sides) like sold at most home improvement stores you won’t have to do these steps.

Once all the parts have been jointed I will use the thickness planer to bring the lumber down to 3/4 of an inch and to make both faces parallel to each other. This will be the final thickness for the shelf parts so if your wood isn’t acclimated yet to your shop I would plane them a little on the thick side so that if you need to mill them additionally later you can.

The final step in the milling process will actually bring our parts down to their final width also and that is to rip them to five and a half inches on the table saw. I use the side I jointed as the reference side on the fence of the table saw.

We now have to cut the boards to their final length and add the mitered edges to each end. Since my miter saw is only really accurate at 90 degrees I like to use the table saw to cut miters for boxes and frames. To help make sure my table saw blade is exactly 45 degrees to the top of the table I use a digital angle finder.

To set up for my miter cuts I used the miter gauge and clamp a scrap board to it to act as material support and as a zero clearance backing for the cuts. I make all of the cuts on one end of each board first.

 

To ensure that all eight boards are cut the same length I cut the opposite miter using a stop block that I clamp to my temporary fence on the miter gauge. This makes for quick and accurate cuts on each of the box sides.

 

Now to attach the two boxes together I will be using half lap joints. Each box will intersect each other at two different points so it is important to be accurate. I first layout the location and width of each of the half laps by using a engineer square and the board that will fit into the joing.

To set up for the cuts I raise the table saw blade till it is exactly half the width of the boards. I screw a scrap board to two different miter gauges to use as the jig for making the half laps. This is one good thing about having a band saw that has the same sized miter slots as my table saw. I recommend testing your set up with some scrap boards before doing this on your actual work piece.

Once all four of the slots are cut for the half lap joints its time to do some sanding. Doing this now before assembly of the boxes will make things a lot easier in the finishing process. The outside edges and faces are sanded to 150 grit sand paper but the inside faces get sanded to 220 grit.

Once the sanding is done (for now) it is finally time to assemble the boxes. To minimize the glue squeeze out I tape the inside edges of the miter joints with painters tape. Then I apply glue to both sides of each joint and align all the sides together and for this first box I used strap clamps.

 To demonstrate another method of clamping boxes with mitered joints I use painters tape again. But not only do I tape the inside of the box sides I also adjoin each of the four sides end to end. I apply glue to each of the joints and then fold up each side onto each other and then add tape to the final joint.

 

I find this method to actually be easier than strap clamps and it still provides enough clamping pressure for a tight joint. once the box is together make sure you check them for square. Since we are joining two boxes at two separate points being as square as possible will make a difference.

Once the glue cures on both boxes it is time to cut the slots for the splines in each of the mitered joints. The jig I use I found a picture of on Fine Woodworkings website and adjusted it to fit my needs. There is a million different versions of spline cutting jigs out there and you just have to find one that you like. Instead of using a stacked dado set in my table saw I just use the standard blade and then adjust the fence and jig to cut the quarter inch slots.

I cut slots for two splines in each joint of each box. Now although this does strengthen a miter joint the main purpose behind these splines is decorative. To make the splines I resaw some scrap walnut I had to a quarter of an inch and then glue them in the slots.

 

Once all the splines are glued in I sand them flush and then finish sanding both boxes. This is the last step before attaching the boxes to each other so it is a good idea to make sure you do all your final sanding now. I sand every surface up to 22o grit sand paper.

Once all the sanding is done I apply some glue to the inside of the half lap joints and then align and attach the boxes to each other. If the joint is tight you might have to use a mallet to help snug up the joint.

Now all that is left is to apply some finish to the shelf. For this project I wanted to use a Tung Oil and decided to use Waterlox. I have used that on several other projects and have been very happy with the ease in applying it and how the finish comes out. To apply the finish I take a few cotton swabs and put them in a small clean rag to use as the applicator. I keep small salsa jars to put the finish in so I’m not keeping the jug open any longer than I need to.

I really like how the Waterlox finish brings out the grain in both the Sapele and the walnut. I apply three coats of the finish, waiting twenty-four hours between coats.

The completed intersecting box shelf

Walnut splines

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