At his local hackerspace [Vincent Sanders] noticed an interesting problem. The stools that they had were great in most cases, but there was one workbench which was very much the wrong height for them. So began his quest to design and fabricate plywood stools which use no glue for their joints.
The Cambridge Makespace (in the UK) turns out to be a perfect environment for this type of project. They already had a CNC router which can cut the plywood pieces, and there are other members who were willing to help train [Vincent] on the equipment. He found a design on Thingiverse which fit the bill, except for the actual measurements. He needed metric units to match the sheet stock available to him. Once converted he put together a stool that didn’t work at all. The thickness of the plywood just didn’t mesh with the tolerances of the joints. After wandering around to different suppliers in town, digital calipers in hand, he came up with a range of actual thicknesses and adjusted his joint design accordingly.
Of course this wasn’t the last revision. Even with the joints working the seat was still a little rickety. He moved to the next plywood thickness offered, redesigning the files to match. His final stool works like a charm, with five or six of them fitting on one standard sheet of plywood.