|A whole bunch of red oak|
I've been wanting to build a Shaker two- or three-step stool for a while. I got some ideas on a design from an image search and came up with this.
|The overall design|
I've read that Shaker step stools were meant to be used directly against a wall. Such stools were vertical at the back.
|Typical Shaker step stool with straight back edges (3-step version)|
|Slanted back edge and matching slant on front edge|
I wanted to dovetail the steps and sides together and needed to decide about dovetail layout. But I also wanted a rail under the front of each step, so I couldn't have a half-pin at the front and back ends of the side boards.
|Upper step dovetail and cross-rail layout|
At the front and back of the step are "half-tails". I needed to have a tail at front to rest on the cross-rail. And I added one at the back for symmetry. I played with the dimensions a bit before deciding on a four-tail design, with the two middle tails being a bit wider than the front and back tails.
I used a similar layout on the lower step, just each tail was 1/4" larger since the lower step was 1" deeper than the upper step.
The two front cross-rails will have their lower edges dovetailed into the sides. The shoulder of the dovetail will add a bit more resistance to racking than if the rails were not dovetailed. There's a bit of added complexity for the lower front cross-rail - it fits into an angled edge, so it's upper edge will need to be beveled to mate well with the underside of the step.
|Upper cross-rail detail|
There will be a cross-rail in the back for even greater stability. It will be dovetailed into the sides as well.
|Back cross-rail detail|
I was not too particular about the vertical location of the back rail. I ended up placing its top edge about even with the top of the first step.
One of the last things I considered was the arch cutout on the sides. I didn't want the feet to be too wide or too small. But the main thing I was concerned about was the amount of wood keeping the right half (lower step portion) attached to the left half (upper step portion) of the stool. I think that's the weak point in this stool design. If the wood is going to fail, it's going to fail just above the center of the arch.
|Original arch detail|
At first, I laid out the arch as a full semicircle. That made the arch 5" high, leaving only 3 1/4" of wood above the arch keeping front and rear portions of the stool together. So I dropped the arch down to 3 1/2" high to add 1 1/2" more wood above the arch to help keep the stool together.
So much for the design. Next time I'll go over the prototype build.