Kids love chalkboards, and the bigger the better. Whether it’s to play a quick game of tic-tac-toe, or to draw a picture, your children will be drawn to, and drawing on this chalkboard.
It is also a great place to tape paper for painting, or leave a little reminder: “Your lunch is in the fridge!”
The construction of this project is fairly straightforward; the writing surface is ¼” plywood set into an oak frame. The sides of the frame extend below the writing surface to form the legs. Two such frames are then joined back-to-back with hinges, making this a portable, yet stable writing surface. A chalk ledge with routed recess is attached to both sides adding a nice finishing touch. It also cleverly conceals the boot lace which limits how far you can spread the legs.
If you prefer to hang your chalkboard on a wall, simply use this plan as a basic guide. Make only one side, and do not extend the sides below what is needed to frame the writing surface.
When selecting lumber for this project, there are a few things to keep in mind. This design calls for four long pieces of oak that form the sides of the chalkboard and the four legs. Choose boards with the grain running parallel to the long axis of the board and that don’t have any knots. Be sure the boards are straight and flat, or thick enough that you can make them so. Use a jointer and thickness planer. I started with lumber that was clear and straight and a full 1″ thick and was able to maintain a thickness of ⅞” for all of the parts. That allows for a more rigid and stable structure when set up.
The Stinky Bits
The least pleasant part of this project is preparing the writing surface It’s very easy, but oh so stinky. So lets get it out of the way at the beginning. First off, make sure you have a proper respirator and adequate ventilation. It’s certainly not something I would recommend doing in an enclosed basement. It’s best done outside on a calm, sunny day. The coating is specialty paint for chalkboards, and is rather thick. It is best applied with a short nap roller.
• Cut the two pieces of plywood for the writing surface (A) to size. Be sure that they are square – it makes assembly go much more smoothly later.
• Sand the face side of the panel through to 150 grit. Fill any holes or gouges in the surface with wood filler.
• Sand the back also, though only to 100 grit (unless you enjoy sanding).
• Pour the chalkboard paint into a small paint tray and roll an even coat on the back of each panel.
• When this is dry, turn the panels face up and apply the paint to the other sides, which will be the two writing surfaces. I wanted a nice smooth, durable writing surface and put on four coats. These coats dry very quickly, so you should be able to get all four done in an evening. Set them aside in a safe place while you work on the frame.
The Pleasant Bits
• Preparing the writing surface first will allow the paint to fully cure while you construct the frame. This is important, as the surface will need to be masked off with painters tape later when the frame is being finished.
• Mill all of your stock to its final width and thickness in one session. Use a jointer and thickness planer if you are working with rough stock. If you’ve purchased your lumber dressed to it’s final dimension, ignore this step.
• Rip your boards to width on a table saw.
• Cut the four legs (B) and the four rails (C, D) to final length. If you can’t cut them as a bundle, then set up a stop on your saw to ensure they are all the same length.
• Carefully lay out the location of the eight sets of mortises and tenons on your stock. When sizing tenons, it is common to make the tenon a little more than one-third the thickness of your stock. I cut mine with a router using a jig, though they can easily be cut using other methods as well (see Sidebar: Cutting Mortises and Tenons)
• The writing surface is held in place in a groove in the frame. Using a bearing guided slot cutter in a table-mounted router is the easiest way to accomplish this. Remember: ¼” plywood is not a quarter of an inch thick, so if you use a ¼” slot cutter the panel will rattle loosely in the frame. I measured the plywood I was using and it came to .212″ thick, or about 20% less. This means cutting the grooves using a 5⁄32″ slot cutter is a two step process (see Sidebar: Cutting Slots in Plywood).
• Tilt the blade in your saw to approximately 8º and, with a crosscut sled or mitre gauge on your table saw, bevel the bottom back of the four legs. Be careful – putting the bevel on the wrong side will mean you will be making another leg… or shortening the other three!
• Place the two top rails face down, with their tops touching on your workbench. Lay out the mortise locations for the hinges.
• Using a spiral bit in the router table, set some end stops and rout the mortises for the four hinge leaves.
• Lay out the seven holes for the chalk ledge and the strap, and drill them out with a 11⁄64″ drill bit. Using a drill press with a fence keeps all of these holes in a straight line.
• Use a ⅜” Forstner bit to counterbore the center hole from the face side. This creates the recess for the knot which is then hidden by the chalk ledge.
• Use a countersink bit from the back on all of the holes, so that the screws can sit just below the surface of the wood and the strap doesn’t chafe on a rough edge.
• Test fit the panels with the writing surface and, if everything fits, glue it up. Be sure to measure the diagonals so that each assembly is square.
Out On a Ledge
• The chalk ledge serves two purposes. It hides the cavity for the knot in the strap, and it is a convenient place to put your chalk. Knowing that this rather small ledge will be subject to a fair bit of pulling and pushing by children, I chose to attach it using four wood screws. This also allows the ledge to be removed and the strap replaced should it ever break.
• With the two sides glued up, sand all of the oak components through to 150 grit. Be careful not to tip the sander onto the writing surface or it will scratch it. Ease the edges slightly. I was trying to achieve an older, more traditional look with this piece and used a Home Hardware Maple Stain (#723) followed by a couple of coats of Circa 1850 Paste Varnish.
• Use painter’s tape to mask off the writing surface. With the edges protected, cover the center with several sheets of newspaper.
• Apply two coats of the Maple Stain, following the instructions on the can.
• Circa 1850 Paste Varnish is a simple, foolproof way to give your project a tough, durable finish. Using a cloth and some steel wool, follow the instructions on the can for an amazing finish that looks hand rubbed and is durable and waterproof.
• Install the hinges and fasten the two sides together. Set the chalkboard on a level floor, and open it until the feet sit flat. Tie a knot in one end of a bootlace, and pass it through one of the sides. Thread the lace through the other hole and mark the appropriate spot for a knot. Tie the knot and trim off the excess. Install the chalk ledge and call the kids…they will find it impossible to resist. This sturdy construction is designed to last for generations.
Cutting Mortises and Tenons
Before I began using a jig to cut M&T joints, this was the basic method I used to cut a 1″ tenon on a table saw:
• Set your table saw fence to the 2″ mark.
• Clamp a 1″ thick block of wood to your table saw fence several inches ahead of the blade.
• Using your saw’s mitre gauge, push the end of the part that is to receive the tenon up until it touches the block. This sets the length of the tenon with the blade projection, setting the height of the shoulder.
• As you move the part toward the blade, it clears the block and you can safely make the cut.
• Repeat this on all four sides. Then begin wasting away the rest of the wood to form the tenon. Make additional passes, each time moving the part farther away from the blade.
• Don’t be too concerned if your tenon has a mildly ridged texture. Spending time smoothing it is wasted, as it provides a key for the glue to grab onto. Cutting the mortises by hand is easy; just follow these steps.
• Select a Forstner bit that is just slightly smaller in diameter than your mortise is wide.
• Drill a series of overlapping holes within the area of the mortise to remove most of the waste; use a fence to keep them in a straight line.
• Use a sharp chisel to clean up the sides of the mortise until the tenon fits squarely and snugly.
• Test fit the two frames to be sure they come together easily and squarely.
• Mill the material for the ledges (E) to the correct dimensions and trim to length.
• Chuck a dish carving bit in your router table and set up some end stops to limit the material’s travel.
• Set your bit for just about the full depth of the recess and start your router. Bring part down on top of the router bit and immediately start to move it. As you move it, press down. This motion makes cutting the recess much easier.
• With the first pass completed, set the router for a final light pass and bring it to the final depth. This stage is not so much to provide any added depth, just to take off enough material to remove any burn marks.
• Using the same method used to bevel the bottom of the legs, bevel the underside of the chalk ledge. Leave approximately ⅛” unbevelled at the top edge.
• Use a jointer or table saw to bevel the front of the ledge in the same manner.
Cutting Slots in Plywood
While ¼” MDF is ¼” thick, most ¼” plywood is under ¼”. You can purchase a 6mm straight router bit from Freud that does a great job of cutting undersized dados and grooves. Or, you can use a 5⁄32″ slot cutter to cut the dados.
Here's how you do it:
• Mark the faces of all of your stock with chalk. These faces will always have to be in contact with the router table through all of the milling process.
• Set up the slot cutter so that the lower edge of the cutter is ¼” above the table – this is the set back for the writing surface.
• The rails can simply be run through once, face down, and set aside The groove runs the entire length of the rails.
• On the backside of the legs, mark the location of the ends of the groove (the edge of the mortise) on the back. Use these as a guide when routing the blind groove between the two mortises. Line up the center of the slot cutting bit on this mark at the end of the groove, and with the part gripped firmly, rout the groove.
• When the center of the bit reaches the second mark, pull the part away from cutter.
• To bring the groove to the final width needed to hold the plywood: first, measure the thickness of the plywood; then raise the cutter by the difference between the thickness of the ply, and the width of the bit. Use a digital caliper for fast and foolproof results.
• Repeat, cutting all of the grooves to bring them to the proper width.