Classroom Hardware • Modular 1x1 Gridfinity

Probability Dice & Spinner Assembly Guide

Featuring 4 mass-balanced 18mm dice and an ultra-low-friction 10-sector rotary needle with quick-swap probability dials. Learn how the spinner is assembled.

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Step-by-Step Spinner Assembly Video

Watch the modular dial disc, spindle needle, and retention cap assemble on a school desk.

Step-by-Step Spinner Assembly Modular dial insert • Micro-clearance friction-free needle

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The Mathematics of Pip Mass Balance

Standard cheap dice drill deep holes for the 6-face and only 1 shallow hole for the 1-face, shifting the center of gravity and heavily biasing outcomes. StackCalc dice scale pip radii inversely (\(r_n = 1.8 / \sqrt{n}\)), ensuring the total displaced plastic volume is identical across all 6 faces.

Step-by-Step Assembly Instructions

Assembling the modular probability workstation.

1

Seat the Base Box:

Place the 1x1 Gridfinity storage box (42.0 × 42.0 × 36.0 mm) on the desk or into a master modular math tray.

2

Select and Insert the Sector Dial:

Choose from the 4 included modular dials (Uniform 10-Sector 0–9, 4-Color Quadrant, Biased Distribution, or Arithmetic Operations). Drop the dial disc into the circular rebate on the spinner lid.

3

Mount the Needle Pointer:

Lower the balanced needle pointer over the central spindle pin. The micro-clearance bore (0.15 mm clearance) allows 30+ seconds of free rotary spin with zero binding.

4

Snap the Retention Cap:

Press the retention cap onto the spindle tip until it clicks. The cap secures the needle against classroom drops while preserving free rotation.