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Wooden Knot Cross Puzzle, OCC, Three Pieces, Kong Ming Lock

3D model description

Wooden Knot Cross Puzzle, OCC, Three Pieces, Kong Ming Lock

This is a simple yet fascinating cross knot puzzle of three interlocking pieces. It may have a Chinese origin, dating back to the days of Zhuge Liang (aka. Kongming, AD 181-234). Easy as it looks, it takes a bit of planning in 3D design. One has to make sense of the physical constraints. While the length of each piece is largely arbitrary; its width has to be three times as much as its thickness. Further, one has to consider the tolerance. This makes a great entry-point 3D design project for STEM teachers and their students. Yes, a bit of struggle is healthy!

In the current design, I have added a 0.5mm tolerance to the OCC slots and a 0.25mm tolerance to the opening so that children can slide them back and forth smoothly. There are two styles with various widths and lengths. Have fun!


3D printing settings






.1 to .2mm



  • 3D model format: STL


STEAM educator, learning from and working with K-12 STEAM teachers to explore new ideas of teaching and engagement. I firmly believe ART is at the core of STEM learning or all human learning! I owe my ideas and designs to the hundreds of K-12 children and teachers and university professors I have had the pleasure of working with, in multiple disciplines-- math, science,engineering language arts, social studies, early childhood education and more! All mistakes, of course, are mine! There is no warranty or liability whatsoever implied or explicit behind the designs or ideas. They are all posted for their potential educational values.

When working with children, please strictly observe all safety and health procedures! Please refer to the NSTA safety guides:




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