“Small Dovetail Box with Dado Bottom” or “Biting-Off More Than I Can Chew”

Dovetail Box - 1So, for my project article this time ’round, I’ve decided to do the next logical step from a single-pin single-joint test piece that really could have gone better in it’s own right… to a 24-pin 4-sided box with a dado and rabbeted bottom.

I’m not building this project this week, but I’ve got the design and layout down pat, so it would be a much easier task to build it with the preliminaries done. In theory.

This project, to be completed as my next shop jobbie, will be constructed using white-pine boards, milled to 3/4″ (~19mm) thick, by 11.25″ (~300mm) wide. This width will be the width of the box, which will feature an overall height of 6″ (~150mm) and a square width/length of 11.25″  (~300mm). Dovetail Box - 2The bottom will be a panel of 1/4″ (~6mm) that is “rabbeted” down to half-thickness on one side (click the second image for a better idea of what I mean by a “rabbet”), with a lip 1/4″ (~6mm) across. The bottom plate will slide into a “dado” (a groove cut into a board) who’s centre is 1/2″ (~13mm) from the bottom, and is 1/4″ (~6mm); making it 1/8″ (~4mm) on either side of the 1″ (~25m) line. This should provide a groove for the tongue of the bottom panel to slide into, and the thicker portion of the base will butt-up against the original wood with a little clearance for expansion/contraction.

Dovetail Box - 3When cutting dovetails, each of the pins are as thick as the adjoining board; in this case 3/4″ (~19mm). When in doubt, use the edge of one board to trace a line along the other, confirm the measurement and score to make a more definitive mark.

All but one of the tails are 1/2″ (~13mm) on the long side, and 1/4″ (~6mm) on the narrow side. The pins (half-tails) are simply half this, and are found on the top and bottom of the brown boards. The largest tail is in the middle (ended up making the measure-math easier, AND makes the work look unique and personal) is a full 1″ (~25mm) at it’s largest point, and 3/4″ (~19mm) at it’s base. All must be cut very, very carefully, and err on the side of caution since it’s easier to pare away some extra bulk than to fill-in or to buy more boards and set these on fire with a certain measure of satisfaction. But that could just be me.

Dovetail Box - 4 Dovetail Box - 5In these two images, you can see how critical the fit is, obviously, to ensure that here are no visible gaps. There ARE solutions to these gap-fill errors, like rubbing-in sawdust to the wood glue before it dries, but we don’t want to prepare shoddy work for band-aid solutions, we want to work towards perfection and beat the learning curve. so, This is your goal. You can see the shape of the boards as they interlock as seen from the outside, and a slightly exaggerated internal corner, without the bottom. The groove must line up perfectly, otherwise the bottom floating panel won’t fit. Remember not to glue this panel, lest it warp during humidity cycles. This sort of box would make an ideal drawer, and indeed is often seen in many wonderful drawers in the American Civil War era furniture, and the British Victorian period, among many others. The joints are tough and beautiful. Just remember, when doing drawers, to attach the knob and the front plate to the GREY boards, in this diagram. That way, when you pull it out of the box, the force will reinforce the joint, and not simply pull it apart; just word to the wise.

For training purposes, it is often wise to use a straight-edge and sharp marking knife to cut a groove on the inside of your panel, and transfer it to all sides.Then using a rigid straight-edge of known thickness, make your thickness marks where necessary; in this case 1/2″ and 1/4″ (~13mm and ~6mm) thick and thin lines respectively. With enough care to preparation, double, triple and quadruple checking to ensure ALL The lines match up, you can save the hassle implied in the following amusing (but painfully poignant) wall-hanging.

IMG_1442Always a good idea to mark an X on the pieces that you intend to cut-away, since I did NOT on my first effort to make a dovetail, and ended up cutting two identical sides… let that be an important lesson to you, and a face-palm for me. Also, be sure to cut on the WASTE-SIDE of the lines/scratches you have delineating the cuts on your board. Always remember that it’s a wise precaution to creep-up on your lines with a chisel, so saw a solid 1/16th (~2mm) off of your lines and chisel away what is left by fractions of a millimeter each time.

For dovetails, you want a nice tight fit that won’t shake apart by gravity. Requiring a mallet to close the gaps results in what is called a “glue-starved joint” and will actually be weaker. You see, typical yellow wood glue (like Titebond I, II or III, Regular, Water Resistant and Water Proof respectively) is basically the same chemical as Lignin (that which trees use to keep their fibers together in nature). In several tests conducted by Matthius Wandel of Woodgears.ca and on his youtube channel, properly glued joints, with common yellow glue, are often stronger than the native wood itself! The link below will take you to his article on wood glue strength testing. The man is a flippin’ genius, study the shit out of his free resources and save yourself a generation of trial-and-error!

Caution: Wood glue won’t stick to itself as well as it sticks to wood, but there has to be enough liquid there to bond the fibers together. Too-loose and you reply on the liquid chemical bond, which is weak. Too tight and you effectively squeeze all the glue out of the joint, starving it. Also, common yellow wood glue is not expensive when considering the small amount needed for joints like this. It sometimes helps to drizzle the glue on, and spread it across BOTH surfaces, to ensure absolute coverage with no air-gaps. When you slide the pieces together, especially with dovetails, mortise and tenons or box joints, there will be a lot of squeeze-out. That’s okay. Just take a handful of the sawdust you just made (for colour-matching properties) and rub it on there with your fingers like you’re sanding. It’ll fill all the gaps, absorb the glue and it can all be swept-up later without mess. I’m a horrifically lazy person when it comes to superfluous steps; I like processes that take care of multiple problems at once.

I have not built this dovetail box yet, but I’ve done enough study to know exactly HOW it’s done, but the actual doing is the tricky part. It’s my hope that I’ll scrounge the fresh board from my local lumber yard and give this a whirl. A 1″ x 12″ by 12′ board will cost me about $30.00 and the 1/4″ x 4′ x 8′ might send me back a little less.That said, I should be able to get 6 boxes out of that one board, and 32 panels out of that one sheet. A sheet of plexi-glass, 1/8″ thick may do just as nice a job, if not cleaner. Will investigate both.

My chief concern is that my grain direction will be going up and down, which runs the risk of severely weakening the tails and pins; they would be MUCH stronger if the grain direction ran left and right. I may have to break down and buy boards that are half as narrow, since I lack a worthy table saw for the task of ripping nice clean pine like this. I also may borrow my neighbors Porter Cable portable palm router (Which is really sweet, by the way, love Porter Cable tools). Could make some lovely fillets (rounded corners) or chamfers (45 degree corners) for the box. Might even use them for the house!


EDIT: If anyone wishes actual plans for this drawing, I can create/compile a PDF file with all the necessary measurements to create the masterpiece. All you need to do is ask!


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