Get to Know the Locks

Please note: the following text is a machine translation by DeepL. The original text is in German and available in the download-section.

When I was surfing for children's toys, I came across the term "Toddler Activity Board". These were all boards with various devices on them that teach the toddler how to operate a switch, a plug, a lock or something similar. This idea grabbed me. But I didn't want a board that would stand freely on the wall, the object should have another use. So I decided on a box with a lid and little doors that are "secured" by various locks.

The individual parts were cut with a laser cutter. This resulted in accurate and easy to assemble parts. If you use other means to make the parts, you will probably need additional material for the little doors.

To ensure that a small reward in the form of a picture appears when a lock is successfully opened, I covered the opening in the cube where possible. I used 3 mm thick MDF for this. The cover is always 2.5 cm bigger in height and width than the door. On three sides I glued a thin, 1 cm wide cardboard strip. The side facing upwards remained open so that the inserted picture can be replaced.

The following instructions were made in retrospect. So not all steps are documented photographically. Instead, I can describe the downside of the chosen construction and suggest measures for improvement:

I underestimated the strength and the grandchildren's ungentlemanly handling of the toy. Although MDF with a thickness of 5 mm is a durable and stable material, it was not enough to securely fasten the hinges. For this reason, I would rather use a plywood of more than 6 mm thickness today. Instead of the individual hinges, piano hinge and thus a large-area fastening could also increase stability.

As download I provide the drawings made in LibreOffice-Draw. If you want to start directly with the laser cutter, you can find the corresponding SVG files.

• 3 boards MDF 5 mm thick, 900 mm x 500 mm
• 1 bord MDF 3 mm thick, 600 mm x 600 mm
• Round wood diameter 8 mm for wooden twist locks
• 20 hinges 15 x 12 mm
• 80 countersunk screws 2.0 x 12 mm for fixing the hinges
• 88 pan-head screws 1.6 x 1.0 mm to reinforce the connection of the teeth of the side walls and to fasten the base and lid
• Screws and nuts for fastening the locks (M2 to M4 as required to match the selected locks)
• Shoe lace (yard goods for cutting to length yourself)
• Transparent acrylic paint for the cuboid
• Different coloured acrylic paints for the doors
• 4 self-adhesive chair felts
• 17 different locks and fasteners*

• Sewing machine (zip fastener, press-stud triangle, Velcro fastener on fabric tape)
• Drilling machine
• Hand drill or small electric drill
• 1 mm drill bit
• Drill bita corresponding to the nuts and bolts used
• Fretsaw
• Pliers
• Metal file
• Hand deburrer (or countersink for the drill)
• Sandpaper of different grades (120, 150, 240)
• White glue

*My list:

• Zipper divisible, approx. 45 cm long
• Some fabric for the zipper
• Velcro, fabric tape (see plan "Klettverschluss")
• Casket closure
• Magnetic closure
• Press stud on fabric triangle
• Shoe buckle with 8 eyebolts (like a shoe)
• Padlocked latch (key attached to shoe lace on an eyebolt inside the box)
• Furniture lock with key attached to an eyebolt with a shoe lace
• Crate lock
• Furniture bolt to secure the double door
• Grendel bolt
• Shock bolt
• Window hook
• Spring hook, shoe lace, 2 eyebolts
• Door chain
• 2 turn latches made of MDF (see plan: "Drehverschluss aussen, Drehverschluss innen")

Cut all parts (MDF 3 and 5 mm) of the cube with a laser cutter.

Prepare fabric fasteners

Drill the screw holes for attaching the hinges with a 1 mm drill: The hinges sit in slots and are easy to fit. One hinge serves as a drilling jig.

If the hinges are not prepared for the countersunk screws, the phases for the screw head must be fitted. To do this, use a pillar drill with a drill bit corresponding to the screw head diameter. Set the drilling depth so that the drill only peels the bevel out of the hinge metal!

Fit all the doors and check that they are properly seated and move smoothly. If necessary, rework the doors slightly with sandpaper. Then remove all the hinges.

Fit the hinges for the lid and pre-drill the holes for the fixing screws.

Attach all the locks to be screwed on to the doors and attach any counterparts to the side walls of the cube. Caution: If the door openings are to have a picture holder neither nuts nor screws must protrude from the inside of the doors. To do this, drill out the screw holes on the inside so that the nut disappears into the recess. Nip off the screws and file them down or shorten them with a mini cut-off wheel.

Remove all screwed locks.

Saw waste MDF (5 mm thick) as glue-on for the eyebolts with a fretsaw to size. Individual eyebolts are given a 2x2 cm plate. Drill a hole in the centre of the plate with a drill of the same diameter as the eyebolt. Glue the small plate onto the door. After drying, drill through the door with a drill thinner than the eyebolt diameter.

For the 8 eyebolts used for the shoe buckle, cut 2 strips of waste MDF (5 mm thivk) 2 cm wide and the height of the door, place the holes and drill them with the diameter of the eyebolt. Then glue the strips onto the door and the cube wall. After drying, drill through the door and the wall with a thinner drill bit than the thickness of the eyebolt.

Break the edges of all the doors with 150 grit sandpaper. Do the same with all the parts for the wooden latches.

If you also want to screw the cube body in the teeth, drill a hole in the centre of each tooth corresponding to the diameter of the screws used. If countersunk or pan-head screws are used, use a hand deburrer to make a phase at each hole.

If you also want to attach fabric parts to the little doors or to the cube walls, now drill the holes through which the thread will pass when sewing the parts on.

The bottom and the top get three countersunk or pan-head screws on each side. Drill the holes according to the screw diameter and attach the phase with the hand deburrer.

Remove any pencil marks on the cube side pieces, lid and base with 240 grit sandpaper.

Attach all non-moving parts for the wooden latches to the doors and cube walls.

Put the cube and lid together. I used white glue for all joints.

Glue the guide rails for the lid into the top of the cube. The rails should protrude approx. 6 mm over the edge of the box. When the box is closed, it stabilises the lid.

Paint all the doors and the outer moving parts of the wooden latches with different colours on the outside.

Paint the outside of the cube and the lid with clear acrylic paint - this works very well with a small roller.

When dry sand with 240 grit sandpaper.

Apply a second coat of paint to the outside of all parts.

When dry, glue 4 chair felts to the bottom of the box in the corners.

Pre-drill holes for the screws that strengthen the joints of the walls, the bottom and the lid with thinner drill bit than the thickness of the srews and insert the screws.

Cut appropriate pieces for the wooden latches from 8 mm diameter round wood. Assemble the latches, making sure that they move easily and that glue does not get into the hole in the side of the cube.

Insert eyebolts.

Fit the hinges to the doors and screw on the locks.

Insert the doors. Check again that the doors move smoothly, if necessary use sandpaper.

Sew on the fabric parts

Attach the hinges to the lid and connect the lid to the cube.

To prevent the lid from opening all the way to the back, limit the path with a piece of shoe lace. To do this, drill a hole in the diameter of the shoe lace in the lid and the side wall of the cube, cut the shoe lace to length, knot one end, lead it through the lid from the outside to the inside, then from the inside to the outside of the cube, knot it again.

Attach the keys to the box with a shoe lace so that they do not get lost.

Cut thin strips of cardboard 1 cm wide and glue them to three sides of the picture holder.

Stick the picture holders behind the corresponding doors. Make sure that the cardboard strips are shifted by about 2 mm on the sides and at the bottom relative to the door opening.

Print out the pictures in the appropriate size and cut the paper to size: Door dimensions plus 5 mm in length and width.

Secure the doors without picture holder to prevent them from being pushed in. To do this, cut the appropriate parts from waste MDF and glue them in place.

This project is my first that I made with the laser cutter at FabLab Zurich.