Measure the coefficient of friction between materials

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Back to school? Surprise your physics teacher with this scientific instrument. A simple two component 3D printed device allows you to measure the coefficient of friction between two materials, dry, wet or lubricated. The shaft is M3 and is fixed to the scale. The table rotates around it. The hole diameter fits to the M3 bolt in such a way that you have to screw the bolt into the table before fixing it with the nut to the scale. In this way there is enough friction to keep the table in position under any angle. Put a sheet of one material on the rotating table (fix it with double sided adhesive tape). Put a piece of the other (or the same) material on top of it and slowly increase the angle of the table. At the moment the object starts to move, read the value. Repeat this two times and take the average value out of three. The table gives the coefficient of friction, which is the tangent of the angle. This table is printed on the instrument in steps of 0.1. If you prefer a value in degrees, take the second version. An overview of several material combinations is can be found on http://www.engineeringtoolbox.com/friction-coefficients-d_778.html https://youtu.be/07UaIDhy9jU