[Note: This entry was actually written in April 2013. I changed the posting date to keep my blog entries in chronological order]
by George Taniwaki
The home remodel plans created by Soderstrom Architects call for wood panels containing square and rectangular wood blocks arranged in a grid pattern. These panels will be used on cabinet carcases, cabinet doors, and as wall coverings. The wood blocks are stained and varnished. There is a 1/2″ wide black border between each block. A detail from the architect’s plan showing the panels is shown in Figure 1.
Figure 1. Detail from architect’s drawing. Courtesy of Soderstrom Architects
After some experimentation, I came up with a way to build these panels that is fairly fast and ensures the grid lines are even, straight, parallel, and square. It involves using 3/4″ plywood and a router to cut the 1/2″ wide grid pattern.
A note on the other methods I tried and discarded. My first idea was to use a circular saw and table saw to cut out individual blocks out of 1/2″ thick solid wood or 1/2″ plywood and glue them onto a sheet of 1/4″ plywood at 1/2″ offset. I experimented using 2″x2″ plywood squares as a test. I noticed that even with a sharp saw blade, cutting plywood with a circular saw is prone to tear out. Further, even when I used 1/2″ wide slats as temporary spacers to align the blocks, I could not attach the blocks to the plywood accurately. The gaps were not even.
My second attempt was to cut the individual blocks as before, but to glue them onto the 1/2″ spacers, once the glue dried, I glued the whole thing to a 1/4″ plywood panel for support (sort of like oversized marquetry). This worked better, but was tedious and the inaccuracies were still visible.
Thus, we will not cut the blocks out and instead use a router to create dados in a sheet of plywood.
Choose the right plywood
The first step in making the panels is to choose the right plywood. We want to match the doors and millwork used in the remodeled house, which are made of solid fir and hemlock. Both species are widely available as S4S stock here in Seattle. However, neither wood is readily available as veneer for plywood, making them expensive. So instead I chose sande. Plywood made from this Central American tropical wood has a grain similar to hemlock, is cheap (about the same price as luan, birch, or poplar veneer plywood), and available in a variety of thicknesses at Home Depot.
For the panels, we will use 3/4″ nominal (18mm or 0.70″ actual), 9-ply, 4’x8′ (1220mm x 2440mm actual) sande plywood. Looking through the piles of plywood at Home Depot, you will notice the quality of individual sheets of sandeply vary widely (it is rated B/C grade, sanded smooth) and sometimes an entire pallet will contain sheets where the veneer has poor grain color and small knots, dark streaks, putty repairs, overlapping core plies showing through, or other defects. You can work around some of these defects. However, for projects where you need to use the entire sheet, it is important to choose the best quality sheets. This may require patience and multiple trips to the store waiting for a pallet of good quality sheets to arrive. For an example of the range in veneer quality see Figures 2a and 2b below.
Figure 2a and 2b. Examples of sandeply with acceptable grain (left) and unacceptable light color and knotty grain, dark streaks, and putty repair (right)
Make panels up to 48″ wide
Once you have the plywood in your shop, cut it to the desired dimensions using a table saw with extensions that allow safe handling of large sheet goods or a circular saw with an accurate shooting board. (For instructions for making a shooting board, see an upcoming blog post entitled “Make shop jigs”.) Make sure your saw is tuned and has a sharp blade. Your life will be miserable if you try to cut sheet goods on a table saw or circular saw that is out of alignment or has a dull blade.
Once the sheet is cut to size, mark the location of the grid lines (Fig 3). (Making a story stick can be helpful.) Set up a shooting board against the mark. Using a router with a 1/2″ straight cut bit, cut a dado at a depth of 0.16″ (Figs 4 and 5). This depth ensures the grain direction visible in the dado matches the direction of the surface veneer. Make two passes with the router to ensure the bottom of the dado is flat.
When cutting sandeply across the grain, the resulting edge will haves lots of fuzz (Fig 6). Remove it using a metal file without a handle. Scrape the fuzz back into the dado using the file. Then hold the file flat against the wall of the dado to cut off the fuzz. Smooth the wall of the dado with a medium grit drywall sanding sponge.
Figures 3 to 6. Cutting the grid lines
Clean off the panel. Fill any defects or voids with wood putty. Apply the light-colored stain to the raised portion (I used a mix of 1 part MinWax Red Oak to 8 parts MinWax Natural). After drying, apply three coats of polyurethane varnish, sanding between coats (Fig 7). Try to keep the dado free of varnish. After the last coat of varnish is dry, remove any excess varnish inside the dado using a utility knife or chisel.
Using a foam brush, apply the dark-colored stain (I used MinWax Ebony) to the inside of the dado (Fig 8). Make sure you cover the entire wall of the dado and produce a clean, sharp edge. The grain of the wood will wick the stain onto the face (Fig 9). Use a clean cloth with a bit of mineral spirits to wipe off this excess stain (Fig 10). Repeat the wiping process every few minutes until the stain stops wicking. Don’t worry if you accidentally wipe some of the stain from inside the dado (Fig 11).
After the stain dries, use a fat chisel-tip permanent marker to fill in any light spots in the grid pattern. Continue until the color is even. Use a clean cloth with a bit of mineral spirits to wipe off any stray marks (Fig 12).
Figures 7 to 12. Staining and varnishing
That’s it. The rest of this blog post will cover making larger panels and finishing the edges of the panels with veneer or molding.
Lap joints make larger panels
One of the projects that will use these plywood panels is the back of a breakfast bar (see blog post entitled “Build a Breakfast Bar) that is about 5-1/2′ wide. A single plywood sheet can only make a maximum 4′ wide panel. Thus, two panels are needed for the back. To join them, use a router to cut a rabbet on both panels to create a lap joint (Fig 13). Note that the lap joint aligns with the dado of the grid pattern. Also note that the rabbet for the lap joint is deeper than the dado used for the grid. This gives the joint more strength. Stain the walls and bottom of the rabbet black and the joint will not be visible. Do not glue the rabbet joint to allow the panels to move.
Figure 13. Schematic showing cross-section of the dado and lap joint
Veneer banding hides end grain
The exposed end grain on cabinet doors, shelves, and dividers made from plywood can be finished many different ways. For our projects, we will hide the end grain using 13/16″ wide hot-melt adhesive birch veneer banding tape. Birch has a color and grain that is a good-enough match for sande. First, cut a segment of tape about 1″ longer than the edge of the panel to be covered. Using an iron set at cotton (400F) and the steam off, tack down the ends of the veneer to the panel, leaving about 1/2″ overhang on each end. The tape is wider than the plywood panel. Rather than placing it in the middle and trimming the excess off both sides, align one edge of the tape to the front face of the panel (the side you will normally see) using your fingers to feel the edge (Fig 14). Don’t let the tape drift away from the edge or else the plywood end grain will be exposed.
Using the iron, melt the adhesive on a two-foot long section of tape (Fig 15). Again, use your fingers to ensure the tape just barely covers one edge of the panel. Use a roller to apply pressure on the glue until it sets (Fig 16). Repeat the heating and rolling process until all of the tape is glued down. If any part of the tape needs adjustment, reheat it starting from the end, peel it up, and repeat the heating and rolling process. Once the glue is cool, place the panel on edge and use a sharp utility knife to cut off the excess from each end of the tape (Fig 17). Lay the panel front-face down and use a sharp utility knife to cut the excess tape (Fig 18). Be sure to keep the knife parallel and flush to the back face of the panel to get a straight cut. Sand both sides of the tape to get a smooth edge (Fig 19).
Wherever there is a dado groove from the grid pattern intersecting the edge, cut out a notch with a utility knife. Keep the blade parallel and flush to the walls to avoid cutting into the plywood.
Stain the veneer tape to match the face of the panel and apply two or three coats of varnish.
Figures 14 to 19. Adding veneer to end grain
Side note regarding Figure 18, there are special knives available to cut veneer banding tape. In fact, I own one, but find it easier to just use a utility knife.
Side note about making cabinet doors. A plywood sheet is often under stress. When you cut it, the two resulting pieces may warp to relieve the stress. Thus, any doors made from these pieces will not be flat and aligned. The solutions are: add a frame around the panel to stiffen the door (in which case you don’t need to add veneer banding), bend the doors flat using steam (I haven’t actually tried this), start over with another piece of plywood, or just live with it.
L-shaped molding hides end grain on outside edges
Where two faces of a cabinet meet, end grain will be visible unless we hide it. We could use the same veneer banding tape solution described above, but then there will be an obvious line in the face of the plywood where the sande panel and the birch veneer meet. This will look worse in the case where the banding is cross grain to the face of the plywood. An alternative solution is to make the joint a design feature by covering the edge with L-shaped molding. A schematic of the design is shown in Figure 20.
To prepare the panels for the molding, set up a handheld router with a 3/4″ straight cut bit set at 0.35″ deep. Using a shooting board, cut a 0.35″ wide rabbet on the back of each panel (Fig 20-2). Dry fit the two panels to ensure the joint is accurate (Fig 20-3). Make sure you have the overlap in the correct order.
Set the router bit at 0.13″ deep. Using a shooting board, cut a 0.15″ wide rabbet on the front of the first panel. Using a table saw, cut off 0.13″ off the end of the second panel. Using the router still set at 0.13” deep, cut a 0.38″ wide rabbet on the front of the second panel (Fig 20-4).
To save time, once you are comfortable with how this joint works, you can skip a few steps. Cut the second panel to the final size (0.13″ narrower than the original dimension). And cut the back side rabbet for the second panel 0.22″ wide (Fig 20-6).
Figure 20. Cutting the rabbets in the panels
The L-shaped molding (Fig 20-1) fits over the two panels (Fig 20-5). To make two pieces of molding, start with a piece of 1″x4″x8′ (nominal) S4S poplar stock. Pick poplar with even color, avoid wood with green or dark splotches. Set up the table saw with a stacked dado cutter and sacrificial fence to cut a 3/8″ wide rabbet 3/8″ deep (Fig 21). Run the stock through one side and then the other. Set up the table saw with a fine tooth blade and rip the stock at 3/4″. To avoid dangerous kickback, keep the wide side of the board against the fence and the molding to be cut on the free side of the blade (Fig 22).
After cutting, sand the molding to remove saw marks, stain, and finish with three coats of varnish. Two panels with rabbet cuts are shown in Figure 26. The finished joint covered by L-shaped molding is shown in Figure 27.
Figures 21 and 22. Cutting the L-shaped corner molding
Flat molding hides exposed edges
The inside corners formed where the plywood panels meet another surface (such as the floor, wall, or countertop) are covered with 3/4″ x 1/4″ flat molding. The molding hides any gaps or uneven lines. It has the same width and thickness as the L-shaped molding to ensure an even appearance where they meet. The 3/4″ thickness means it will also fit well with base molding and shoe molding on the wall (Fig 27).
To make eight pieces of molding, start with 1″x6″x8′ (nominal) S4S poplar stock and use a table saw to rip eight 0.25″ wide strips off of it. As with the corner molding, to avoid dangerous kickback, keep the wide side of the board against the fence. To make additional cuts quickly, use a stop block jig to set the free side at 0.25″ (Fig 23). After making each cut, adjust the fence to align the stock to the stop block to set the thickness to 1/4″. Repeat until all eight pieces are cut (Fig 24).
After cutting, sand the molding to remove saw marks, stain, and finish with three coats of varnish. A photo of the flat molding in use is shown in Figure 27.
Figures 23 and 24. Cutting the thin flat molding
Note regarding Figures 22 and 23, the table saw blade guard and splitter removed to show details. Always have a guard and splitter in place when using a table saw.
Apply the molding
To use the molding, glue it to the panels and tack it in place using brads. Attach the corner molding on first (it is nearly always vertical, Figs 25-1 and 27), then the flat molding on any vertical edges (Figs 25-2 and 17), and finally the flat molding on any horizontal edges (Figs 25-3 and 27).
Figure 25. The order to apply the molding
Figures 26 and 27. Edges formed by a panel meeting another panel, a wall, and floor before molding is applied (left) and after (right)
Note that in the before photo (Fig 26) a piece of horizontal molding is already installed on the lower left. In the after photo (Fig 27) the base molding and shoe molding has been applied to the wall.
All drawings and photographs by George Taniwaki unless otherwise noted