Coil Hinged Box

We needed to replace the money box we used at YuKonstruct for members to pay for the supplies they use. The box we were using up until now, required you to actually dismantle and reassemble the box every time you needed to make change! This could be seen as a deterrent to theft, but since we use an honour system, it was very impractical and challenging for some...

Size wise, a 5" cube seemed like it would more than meet our needs. In solving the hinge requirements of the box, I came up with a number of different ideas, but challenged myself to see if I could use successfully use a plastic coil binding, sacrificed from one of my notebooks.

It worked so well, that I am sure I will be making many more coil bound hinged boxes in the future!

Step 1: Materials and Equipment

• 1/2" plastic coil from spiral bound notebook
• small pliers
• hair elastics (optional)
• wooden button (optional)
• 1/8 inch birch plywood
• wood glue (Titebond III)
• thick elastics and/or clamps
• sandpaper
• access to laser cutter
• design files (created in CorelDRAW)

Step 2: Cutting Out Box Pieces

Using the CorelDRAW design file, set your print settings and cut out your box using 1/8" plywood. I used speed/power/frequency settings of 12/80/20 to cut birch plywood on a 60 watt Epilog Fusion laser cutter.

I used scrap wood left over from a redesigned computer case, so ended up cutting out my pieces a few at a time and had some pieces scattered with random holes.

Step 3: Sizing Your Coil

If you haven't already got a coil, you can remove one from an old spiral bound notebook. The coil I used had a 1/2" diameter.

Count the holes on one the top or bottom side of the box hinge, and add a few extra for good measure. Count the same number of coils on the back of your sacrificial notebook, and snip the length you need. Back out the section of coil from your notebook.

Note: When designing the hinge, I went on-line to see what the standard hole spacing was for coil bound books. I learned that it was 4:1, so I placed the holes 4 to an inch and used a diameter of 3/32".

Step 4: Adding the Coil

Not being sure how this was going to work, I assembled the box pieces and held it together with elastics before gluing it, while I attempted to add the coil hinge.

Hold the coil in one hand, line it up with the holes on your box, and insert one end into the first logical hole (photo).

I designed the hinge holes to alternate up and down and be offset to each other, leaving an extra hole on one end of the bottom and the other end of the top. Because I was inserting the coil from the right side, on the inside of the box, I had to skip the first hole to get the coil started, and then insert it in that first hole at the end, after I had moved the coil all the way through (not a big deal, but I will make sure the extra hole better corresponds to the angle of the coil for the next design).

Manually feed the coil into the first few holes on your box alternating up and down and stretching the plastic over the edge of the box to get it started. Once you have a few rounds in, it will get easier and easier to feed the coil. Because the holes are evenly placed, the coil end almost starts to look for the next hole!

Feed the coil all the way through and back it up to go through the first hole, if you skipped it.

Step 5: Fininshing the Ends of the Coil

Trim the extra length of coil extending on either end of the hinge, leaving enough to allow you to bend it back on itself. Using small pliers, bend the extra length of coil towards the opposite end of the coil, and tuck it inside. This should keep the coil in place (photo).

Step 6: Tweaking the Design

Once I had the coil hinge in place, I noticed a couple of things about my design that I wanted to tweak, so I was happy that I hadn't glued my box together yet!

The size of the coil, and the distance between the two rows of holes, created a space of about 1/8" at the back. This actually was perfect spacing for the hinge. It worked really well and didn't get bound up at all. However, it meant that the front and sides of the box didn't line up properly (photo). To solve this, I went back into my design and added an 1/8" to the front and sides of the lid of the box, and removed a 1/8" square on the one corner at the back of one side of the lid, to allow for the hinge to continue to work well and to be symmetrical with the other side.

I then re-cut the three pieces.

The new sides are on a separate layer in the design file.

Step 7: Adding a Closure

Adding a closure to the box can be done at any time, but since I wanted to add a few holes to be able to thread hair elastics through my box and to add a small triangular button, I did it next. Being an after thought, I carefully positioned my pieces back into the laser cutter and added some extra holes (holes are on a separate layer in the design file). This could have been done with a hand drill, but I was in laser cutter mode.

I then cut the metal connectors off the hair elastics, threaded one through the box, and one through the button and the box, and tied them in on the inside of the box with reef knots.

Step 8: Glue and Reassemble Box

To glue the box pieces together, I started with the lid. Use a small paint brush to apply a bit of glue to the top surface of each of the finger joint tabs (photo) and leave the hinged side to the end. Once all sides are glued, wrap thick elastics around the lid in both directions to keep it tightly together.

Next, glue the bottom pieces of the box together, again working on one side at a time and ending with the hinged side. Wrap elastics around the bottom of the box and then clamp the whole box together in all directions if you can, making sure that the corners and joints are in position.

Let the glue dry. Once it is completely dry, remove the elastics and clamps, and lightly sand the edges of your box.

Step 9: All Done!

Because I was using up scrap wood for parts of the box, there are random holes in the lid and the odd hole in the side that ended up in a joint. The holes do not affect the function of the box, and I don't mind the way they look, but they are not included in the design file, in case you are wondering!

Also, since I was so focused on the hinge, I didn't really mention the other design features. I added a dip in the lid at the front side of the box to help seat the lid and a slant to the sides of the box to make it lower at the front when the box is sitting open. The hinge allows the lid to sit nicely at a ninety degree angle and stay open.

I was very happy with the way this turned out, and will be curious to see what other applications of the coiled hinge others come up with!