Want to go retro with your calculator watch? No, not the 1980s. How about two millennia before that? We're going to make a bent wood bracelet with a miniature, working abacus built into it!

These instructions are for a traditional Chinese Suanpan style abacus with a 5+2 bead configuration, but you could easily adapt them to a Japanase Soroban style with a 4+1 bead configuration.

Step 1: Tools and Materials

Materials

Wood veneer
You'll need five pieces approximately 1.5" wide by 8" long. The wood I used is bubinga from Rockler.
Wood glue
I used Titebond III wood glue.
Superglue
Seed beads - size 8/0 (approximately 2.5mm diameter)
Head pins - 21 gauge silver, 2" long
Aluminum sheet cut from a soda can
Baking parchment
Clear gloss polyurethane wood finish
2x4 lumber - 3" long

Tools

2 hose clamps (minimum 2" diameter)
Screwdriver (to tighten the hose clamps)
Coping saw
Sandpaper, assorted grits
Metal ruler
Scissors
X-Acto knife
Tweezers
Wire cutters
Small brush to spread glue
Pin vise and a bit the same diameter as your head pins
Power drill and a bit wide enough for your coping saw blade to pass through

If you've got access to a band saw or jigsaw it'll make step 2 go a lot faster, but it isn't required.

Step 2: Make the Bracelet Form

The bracelet is made by laminating layers of wood veneer together around a form, so the first step is to make that form.

Draw an oval on the 2x4. Remember that you don't need to be able to fit your hand through the oval because the bracelet will have an opening to pass your wrist through. Mine was about 2.25" on its short dimension and 2.75" on its long dimension. You could draw the oval on a piece of paper first, cut it out, then see how roomy it is on your wrist.

Cut the form from the 2x4. If you don't have access to a jigsaw or band saw, you can use the coping saw. Smooth the sides with sandpaper; the finish on the inside of the bracelet will only be as good as the finish on the outside of the form.

Step 3: Cut the Veneer

With a metal ruler and an X-Acto knife, carefully cut the wood veneer into five 1-5/8 inch strips. You want the edges to extend slightly past the 1.5" width of the form.

The cleaner and straighter you can make the cut, the easier it will be to use the veneer.

After cutting the veneer, you'll need to cut a strip the same size from an empty aluminum can. It's easy to do if you poke a hole in the can with a knife, then use scissors to cut all the way around. Cut down the side, then cut all the way around again. Once you have a strip separated you can clean up the rough edges with scissors.

Step 4: Gluing the First Two Layers

Get your hose clamps ready by opening them just wide enough to slide over your bracelet form.

Wrap a piece of veneer around the form to test the fit. If there's any overlap, mark and then cut off the extra. Cut a second piece to the same length.

Cut a piece of baking parchment slightly wider and longer than the veneer. Wrap it around the bracelet form to keep any glue from sticking to the form and accidentally glueing the bracelet to it.

Spread a thin layer of glue on one side of a piece of veneer, making sure that you cover the entire surface. Put another piece of veneer against the glue and wrap them both around the form, placing the gap at the bottom of the form (on the long edge).

Wrap the aluminum sheet around the veneer on the form, and encircle it with the hose clamps. The aluminum sheet spreads the force of the clamps so they don't indent the wood. Keep the screw mechanism of the hose clamps at the bottom of the bracelet where the gap is between the wood. Tighten the hose clamps; really crank them down.

Wait overnight for the glue to dry.

Step 5: Gluing the Middle Layer

Loosen the hose clamps and remove them and the aluminum sheet. The two layers of veneer will spring open slightly, but should pretty much keep their shape around the form.

Cut a piece of veneer lengthwise into 6 strips about 1/8" inch across. That 1/8" will be the distance between the rods of the abacus, so try to get them as equally sized as possible.

Mark the exact center of the bracelet and glue three of the thin wood strips on each side, with a millimeter of space between each one. Clamp it tightly with the aluminum sheet and hose clamps, ensuring that the pieces don't move out of alignment. The gaps between these pieces will be the pilots holes to help drill later.

When the glue has dried, remove the clamps and wrap a piece of veneer from 1mm past the last piece to the bottom in order to find the size. Trim any extra length. Repeat on the other side. Apply a thin layer of glue and then clamp both pieces on with the aluminum sheet and hose clamps.

Step 6: Gluing the Last Two Layers

Test fit the last two pieces of veneer around the three layers of the bracelet you've already built up. Trim any extra length.

Put a thin layer of glue on the bracelet while trying to keep it out of the channels for the rod. Wrap the fourth layer of veneer around, then the metal sheet and the hose clamps as you did with previous layers. Use a thin sewing needle or a piece of wire (your head pins won't fit yet) to clean any still-wet glue out of the channels that will act as pilot holes later for drilling.

Let the fourth layer dry, then glue and clamp the fifth layer.

Step 7: Squaring the Edges

The bracelet is built up to its final thickness, but the edges are still rough and uneven.

Remove the aluminum sheet and clamp the bracelet around the form, making sure that all of the edges extend past the form. Put a rough grit sandpaper face-up on your table or workbench, then move the bracelet back and forth across it to even up the edges. Keep the form square to the paper, and as you get close to the form, switch to a finer grit for a smoother finish.

The job will go more quickly if you've got a belt sander, but be careful you don't sand into the form.

Use the coping saw to cut the opening at the bottom for your wrist to pass through. An opening of 1" to 1.25" should be enough to squeeze through, depending on the size of your wrist. Make sure that it's centered at the bottom.

Step 8: Marking the Openings for the Abacus

Before cutting the openings for the beads, you need to mark where they'll be. Measure the length of 7 beads to find the height of the lower opening, then measure the length of 4 beads for the upper opening. Add the two together, subtract that from the total width of your bracelet (1.5" if you're using a piece of 2" lumber), then divide by three. This will give you three equal sections for the top, middle, and bottom supports.

As an example, if 7 beads equals .5" and 4 beads = .3125" you would add those together to get .8125". Then subtract it from 1.5" to get .6875". Divided by 3 would give .229" for the top, bottom, and middle supports, or just a little over 7/32".

Measure in that distance from each side and mark with a pencil. Add the length of the 7 beads, and mark there. From the other side, add the length of the 4 beads. Use a flexible ruler or a credit card to draw straight lines on the curve of the bracelet.

To determine the width of the openings, draw a line between the outermost pilot holes on each side. Offset each line by the width of one bead. The third picture should make clear the relative positions of all the lines.

Step 9: Cutting the Openings

With a bit large enough to make a hole that your coping saw blade can pass through, drill a hole in each of the two sections to be opened. Take one end of the saw blade out of its frame, thread the blade through a hole, and reattach it to the frame. Then carefully saw the opening, keeping the blade perpendicular to the bracelet. Stay to the inside of your line, because you'll clean it up with a sanding stick. Detach the blade, insert it through the remaining hole, and repeat.

When the openings are roughed out, wrap a piece of sandpaper around a small block of wood and sand the edges smooth. Start with a rough grit to quickly get close to the lines you drew, then switch to a finer grit for the final finish. An X-Acto knife is useful to get really crisp corners.

Step 10: Drilling Holes

Use your pin vise and the miniature bit to drill out the holes for the rods. The gaps between the thin, crosswise veneer strips from step 5 will act as pilot holes to guide the bit through in a straight line.

Step 11: Final Finish

Sand a radius on the corners at the opening of the bracelet so that you can pass it comfortably over your wrist to put it on.

Sand the inside and outside of the bracelet with progressively finer grits, and smooth all of the corners slightly so the bracelet is more comfortable to wear.

Clean off any dust, then apply a thin layer of gloss polyurethane (or whatever wood finish you prefer). Let it dry according to its instructions, then sand with a fine grit paper or with steel wool. Apply additional coats, repeating the sanding between each until you reach your desired finish.

Step 12: Rods and Beads

Slide a head pin partway in, thread the appropriate number of beads onto it (5 for the bottom section, 2 for the top), then slide it into the next section and add the remaining beads there. Push the pin through so it's flush with the opposite side. Pull it back slightly, cut it flush, then push it in with another pin so that both ends are set back from the edge of the bracelet. Repeat for each pin.

To fill the holes, sand some veneer strips and save the sawdust. Mix it with superglue to get a paste, then press the paste into each hole with a toothpick, small scrap of wood, or even an extra head pin. Using sawdust from the same wood as the bracelet will make the filled holes almost invisible. When the glue dries, sand the edges down so the only superglue remaining is in the holes. Reapply a coat of finish to the edges — being sure not to get any on the beads — and let it dry.

Your abacus bracelet is now ready to wear!
For instructions on how to calculate with an abacus, see this Wikipedia article.