This time I built a kid’s chair, modeled after one my wife’s parents had at their place.
Flipping it upside down changes the seat height — so it works for everyone from babies up to preschoolers.
Turn it on its side and it doubles as a step stool. A multi-purpose chair, basically.
You only need a single board to make it.
I’ve also included the cut sizes and a materials list, so give it a try.
Materials and Tools
■ Required materials and tools
・Wood: 350 mm × 910 mm × 18 mm thick (pine glue-laminated panel or similar) × 1 board
・Cordless drill/driver
・Circular saw (a hand saw also works; or have the home improvement store cut it for you)
・Screws: 3.8 mm dia, 28 mm long, coarse-thread deck screws (close to this size is fine)
・Hand saw (for trimming the dowel plugs that hide the screw heads — a “no-set” saw works best; explained below)
・Sandpaper for finish (grits #120, #240, #400)
■ Nice-to-have
・Random orbital sander (makes sanding much easier)
・Trimmer / palm router (for the rounded-edge profile — a sandpaper-only approach also works)
Cutting and Assembly
I used pine glue-laminated panel.
This material is sold at most home improvement stores in Japan.
I like its light tone, so I use it for DIY projects fairly often.
Cutting the boards
I cut the panel into 4 pieces at the dimensions below.
I used a circular saw.
(You can also have the home improvement store cut everything to size for you when you buy the wood.)
From a single 350 mm × 910 mm × 18 mm panel, you can get all 4 pieces.
(Board thickness is 18 mm.)
Test-fitting the pieces together (no fasteners yet).
Sizes look good.
Biscuit joinery (optional — feel free to skip)
Normally I’d just screw the pieces together, but for fun I tried biscuit joinery this time.
※ You can absolutely skip this step.
In fact, even after using biscuits I felt the joint wasn’t strong enough on its own, so I ended up adding screws too.
The dedicated tool for biscuit joinery is called a “biscuit joiner” (plate joiner). I don’t own one, but you can buy a special bit that lets a regular trimmer/router do biscuit slots — that’s what I used.
Cut a biscuit slot into the side edge of the board with the biscuit bit.
Slot done.
For the matching slot on the face of the other board, I used a regular straight bit.
Apply Titebond wood glue inside the slot, drop in a biscuit,
and assemble.
Screws + hidden screw heads
Now to lock everything together with screws.
I want to hide the screw heads — partly for looks, and partly so a kid won’t catch a hand on the head.
Here’s a diagram of how the screw is hidden inside a counterbore that’s then plugged with a wooden dowel:
Screws: 3.8 mm dia × 28 mm long, coarse-thread deck screws — bought at the home improvement store.
Drill the pilot hole with a power drill.
Start with a thin bit (~1.5 mm). A small bit is easier to start exactly on the mark.
To hide the screw head, I’ll counterbore down into the surface.
The screw head diameter measured 8 mm:
So I’ll counterbore with a 10 mm bit down to the depth shown.
The yellow masking tape on the bit is a depth marker.
Trying to drill straight to 10 mm in one shot tends to wander, so step the bit sizes up gradually (e.g. 1.5 → 4 → 8 → 10 mm).
The next photo shows the 8 mm step.
Drill down to the masking-tape depth.
Final 10 mm counterbore done.
Drive the screw down inside the counterbore.
Once the screw is set, drop wood glue into the hole,
and push a 10 mm wooden dowel into it.
Wooden dowels are sold at the home improvement store.
Now saw off the dowel where it sticks out above the surface.
For this cut, a “no-set” Japanese pull saw works beautifully.
(If you don’t have a no-set saw, just cut with a regular saw and clean up with sandpaper.)
＜About saw “set”＞
“Set” refers to the way saw teeth are bent slightly outward to the left and right.
That bend lets the blade pass through the wood smoothly and keeps sawdust from clogging the kerf.
A no-set saw cuts more slowly, but it cuts on a precise plane.
When you’re flush-cutting a dowel like this, the lack of set means the saw won’t scratch the surrounding surface.
The no-set saw I used here is the “Z-Saw Handy 160”.
I couldn’t find one at my local home improvement store, so I ordered it online.
Dowel cut flush. That finishes the screw + plug step.
Finishing (Round-overs, Sanding, Wax)
Construction is done. Last steps:
・Rounding the edges
・Sanding
・Waxing
Rounding the edges
Since this is for a kid, I want softer edges for safety.
I used a roundover bit on a trimmer/palm router.
※ If you don’t have a trimmer, you can knock the edges down with sandpaper.
Rounded edges done.
I’m using a Ryobi (now Kyocera-branded in Japan) trimmer. It’s well regarded as a great-value, beginner-friendly tool, and that matches my experience:
Where the trimmer couldn’t reach (inside corners), I used a wood rasp to round things off by hand.
(In hindsight I should have rounded those edges before assembly… lesson learned.)
The wood rasp I used:
It removes wood pretty aggressively.
Sanding
Final sanding pass.
I used a power sander, but for a piece this size, hand-sanding with sandpaper is fine too.
I worked through grits #120 → #240 → #400.
Lower grit numbers = coarser; higher numbers = finer.
For finishing furniture or prepping for paint, going up to about #400 is generally enough.
Wax
I’m leaving the wood unstained and finishing with a clear wax.
I used Watco Wax (clear).
You could also stain it and topcoat with varnish — that’s a perfectly good alternative.
This was old stock from my workshop — looking it up now (Sep 2024), Watco Wax W-15 doesn’t seem to be available anymore.
Watco’s official site says: “Due to various circumstances we will discontinue this product once current stock runs out.”
If you want a similar clear wax finish, Turner Color “Antique Wax — Clear” is a solid alternative:
Brushed it on (you can also rub it in with a rag).
The wood color goes a little darker — like wet wood.
About 30 minutes later, buff with a clean rag.
Finished
Done!
As shown below, flipping the chair upside down changes the seat height.
It also makes a great little step stool.
This one’s beginner-friendly. (Feel free to skip the biscuit joinery section.)
Why not give it a try for the kids?
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