Folding Table

posted in: Art, Math, Metal, Wood | 1



Two elevator pitches to market this table:

Do you have a room with walls that meet at 90 degrees AND other walls that meet 60 degrees? Tired of buying different tables to fit in each corner? Look no further!

Finally a table that accommodates the non-committal RSVPs of the millennial generation! Planned a dinner for four and one friend cancels at the last minute? No worries, quickly transform your four person table into a stylish three seater.

This table is based on a hinged dissection of a triangle into a square. The table was my final project for my welding class. I found an explanation of this hinged dissection (called Dudeney’s Dissection) in How Round is Your Circle by John Bryant and Chris Sangwin. I began by drafting the geometric construction on paper and then in AutoCad. The cool thing about geometric constructions is you can draw them using only a straight edge and a compass. Below is a sample of my drafting for the table.


Geometric construction in AutoCad (green lines were for layout)


Triangle and square positions. Yellow circles represent leg placement and purple represent hinges.


The four moving pieces of the table with box tube layout.

I decided to build the table with a 1″ steel box tube frame and wooden inlay. Since the angles had to be exact, a degree off would result in a gap in the table, I printed out the layout full scale and built a jig directly on top of the drafting. I checked each cut against the full scale drafting to ensure the angle was correct.


 Table section in welding jig.


Welded sections assembled in the two table positions.

The next big challenge was the hinges. Each hinged section had to move a full 180 degrees. This would not be difficult with wood, since you could just inset the hinges like you would with a door. But with thin (16 gauge) tube, I did not think that I could inset them accurately. Further more, the hinge had to be strong enough to support the table in the resting position and while being rotated. After lots of research and a few prototypes, I ended up creating a simple hinge with a bolt that mounted to the underside of the table.

 hingeHinge mounted to underside of table.

Finally, I made some simple legs out of schedule 40 pipe and through bolted them.




Overall, I’m happy with how the table turned out. I plan on making another version entirely out of wood with the hinges better integrated into the design. The table is a little unstable (it works fine as a side table, but I wouldn’t want to eat on it), since there is no locking mechanism to hold it in position. On my next version I plan on adding some sort of lock to the bottom of the table.

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