Wooden Locking Mechanism - Canadian Woodworking Magazine

Home Project: If you are looking to spice up your next project, you might want to try adding this simple locking mechanism.

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Wooden Locking Mechanism



Photos by Kelly Snake

This country chic recycled chest of drawers features an eight-dial wooden combination locking system. Each of the center dials unlocks one of the drawers. This locking system is easy to construct.
 
The dresser itself is pretty straightfor­ward, mixing new and recycled materials to come up with something exciting, while being on a tight budget. You can build this dresser by any methods that you are already comfortable with. You can choose conventional metal drawer slides or go for the old-fashioned runner style. The important part to pay attention to in the side-by-side drawer design is the space between the adjacent drawer sides (when closed) should be no less than 2 1/2", but no greater than 3" (the larger the diameter is, the taller the drawer must be to be able to fit both dials in the avail­able interior space). The drawer faces should overlap the face frame so that you can’t see into the chest and see the lock­ing mechanism.
 
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The material I used for the chest sides, top and drawer faces is recycled “shipping container grade” veneer core plywood, a good sturdy material that saves loads of time and work, not hav­ing to go through the old clamp and glue routine to make wide panels. The top and drawer faces will be wrapped with a 1/2" thick pine edge banding, so no ply­wood edges will be seen once this chest is complete.
 
With the chest sides lying flat on the bench carefully layout the drawer size and spacing. Within the inner chest cav­ity, the chest is built by using 3/4" x 3" wide x 24" long pine and plywood pieces that I simply screwed from the outside of the chest sides and then filled the coun­tersinks with shop made wood plugs. Perhaps this is not the most elegant way of doing the job, but it does work well for rusticated painted pieces.
 
On the face side of the chest frame it with a standard piece of 1 x 2" pine. Painting the chest of drawers also helps to blend the use of the plywood with the use of the new pine as well. Nothing very complicated here, the 1 x 2" pine face frame is simply glued and nailed onto the face side of the chest. Use a nail punch to set the nails just below the surface and then putty over the nail holes. The rails of the face frame and the center divider are half-lapped for added strength. The better you can layout and execute this operation the easier the rest of the assembly will be.
 
It is a good time to mention that you may want to finish your chest of draw­ers before you build the locking system; because once the dials are glued together they are there permanently.
 
The dial parts
I cut ¼" thick x 2 ½" discs on my band-saw using a circle-cutting jig. Glued to them are some ½" thick x 1 ¼" maple discs I bought at the local craft store. The thicker maple disc adds thickness (and therefore gluing strength) to the thin birch disc. Once out of the clamps, run a ¼" drill bit through the two pieces so there is a clean hole through the center. This pair will become the inside part of the dial lock. The small knobs are also found at the craft store. Carefully nip off the “pin” end of the knob and belt sand flush. Use a strong set of spring clamps to hold the knobs while cutting. Be very careful with this, as the knobs are small parts and can fly out of the spring clamps if not careful. Drill a ¼" x 3/8" deep hole into the knob to receive the ¼" shaft.
 

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All the Parts – At this stage, the two types of round wooden disks are glued to each other and the 1/4" shafts are ready for assembly. The turned knobs still need 1/4" diameter holes drilled in their base to accept the shafts.
 

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Careful Layout – With the help of a couple of spacers, mark the height of each pair of disks then remove the disks and add a center mark on the inside of the stile. This is the location of each required hole.
 
Drill holes in the stiles
With the dresser face down on your bench (and hopefully with the back off), lay two dial disc pieces face down on the center divider. Space them between the lower drawer runner and each other by using pieces of scrap that are about 3/8" wide. Mark the center holes with a pencil. This mark is a general mark only, and will need to find the center of the center divider before drilling. Drill through the center divider with a drill bit slightly larger than ¼". This will give the dial shaft room to rotate easily, but not so sloppy as to work poorly. Make sure you have a scrap block in place to reduce tear-out on the face side of the center divider. When installed, about 3/4" of the shaft should protrude from the back of the stile.
 
With the drawer in its closed posi­tion, dry fit the dial assembly. You may not want to push the dial shaft all the way into the dial discs if the fit is tight. When rotated, the dial discs should not touch either of the drawer sides. If they do, sand them to fit on the belt sander and retest. Ideally, the birch disc is 1/4" smaller in diameter than the distance between the two drawers.
 

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The Right Length – When inserted through the hole in the stile, the shaft should protrude 3/4", giving enough surface area to glue the disks to.
 
Cut the notches
Mark the position on the drawer where the dial disc comes closest to the drawer side being locked. This line is where you will attach the 1/4" x 1/4" lock strip to the drawer side. The lock strip engages with the disk if the disk is in the “locked” position, but does not act as a drawer slide in any way. Mark a vertical line on the drawer side indicating where the lock strips starts (factor in 1/16" for clear­ance). Mark in place and cut a notch out of the dial disc that’s slightly larger than the dimensions of the lock strip. I used spring clamps to hold the small dial disc while cutting the notch on the band saw, though a hand saw can also be used. The amount of slack in the notch affects the precision to properly align the dials to be unlocked. For example, it may be better to have wider notches if you are making this for a child, where they’re more likely to enjoy the piece if it isn’t too picky for them to open. Re-insert the drawer and dry fit the dial assembly again to check for fit one last time. If the dial discs don’t rub on the sides of the drawers and the long lock strips slides through the notches properly, then all is okay to glue the two dial assembly parts together. To do that, use a small applicator to spread a bit of glue inside the dial disc center hole only. With the dial knob and shaft inserted through the center divider, join the two parts. It is wise to use a small spacer to keep the dial parts from getting too close together. A business card usu­ally works well.
 

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Before the Notch – With just enough room to clear the adjoining drawers, it’s now time to mark the dial for the notch.
 
With the drawer in the case, place the lock strip into position on the drawer, aligned with the notch in the disk dial. Measure and mark the location of the strip on the other end of the drawer to keep the lock strip level once assem­bled. Remove the drawer from the chest and glue and nail the lock tab onto the drawer side. Repeat the same steps for each drawer. On this piece all the upper knobs (per pair of drawers) will open the right drawer, while all the bottom knobs will open the left drawer. Mixing these up can add a twist in solving the combination.
 

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Add the Lock Strips – With the notches cut into the dials, the lock strips can be positioned on the sides of each drawer. Here, the front of the lock strip is in place and the location of the back of the strip is being marked.
 
Add the combination
Now comes the part where we add the secret code to the locking system. For me, I chose one eight-letter word: “RECYCLED”. You can divide it up into two words if you like, so long as it has eight digits in total. To turn these letters into numbers, just look to your telephone keypad for the translation – RECYCLED turns into 73292533. Next, imagine a clock face surrounding the knob and set the numbers accordingly. So, 7 would be set to 7 o’clock, 3 would be set to 3 o’clock, etc.
 

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Combination – Once you’ve decided on a combination, turn the discs to their unlocked position and mark them. First translate the eight-letter word into an eight-digit number using the formula on a phone keypad. Then add the appropriate marks on the knobs, keeping the small hand of a traditional clock face in mind.
 
To set your combination, open all of the drawers just enough to engage the dials so that they can’t rotate, now mark your combination onto the lower part of the knob. If you have a lot of play in the notch, try to find the center of that distance and mark your indicator point there. You can burn or paint the mark on to make it stand out.
 

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Unlocked – When the dials are in the unlocked position, and the lock strips are attached to the sides of the drawer, there is just enough clearance to allow the drawer to slide open.
 
The finish on this piece is two coats of a country green latex paint, sanded between coats. After that using a palm sander with 120 grit and, on the lowest speed, break all the edges on the chest carcase and on the drawer faces. Also sand wear spots in the center of each drawer face and on the top of the chest sand a larger wear spot in the center. This is a great opportunity to give the chest some distress marks, or charac­ter, as I call it. Giving it a few bumps and bruises will help it to look like it has already lived a full life. After that, take a stain rag (golden oak colour) and wipe down the entire painted surface; the sanded edges and little nicks will pick up the stain, while the painted green parts will darken slightly.



KELLY SNAKE
Kelly Snake

When Kelly isn't in the shop he's out scanning the antique malls for unique wooden boxes with potential for a creative transformation into a one-of-a-kind puzzle boxes.