How dice are made

Casino dice have their dots drilled out and refilled with paint of exactly the same density as the plastic.

stations: 7
things upstream: 70
raw sources: 21
steps from the ground: 10

The short version

Mass-market dice are injection molded in a two-piece steel mold. The sprue is cut off, the dice are coated in paint and a tumbler rubs it away everywhere except the indented numbers, rounding the corners too. Casino dice skip all that: they are machined from plastic blocks, drilled at each pip and refilled with material of the same density, so every face weighs the same.

Inject the plastic

Molten acrylic or resin is forced at high pressure into a steel mold, usually two pieces pressed together. It cools, and the mold opens to eject the dice.

Goes in
Plastic
Trim the sprue

Each die leaves the mold with a small nub where plastic entered, and that nub is cut off.
Paint and tumble

Dice are coated in paint and tumbled. The action strips paint from everything but the indented numbers, and rounds and smooths the corners.

Goes in
Paint
Machine casino blocks

Casino dice start as blocks of cellulose acetate rather than molded plastic, machined to a tolerance of about 1/2000th of an inch.

Goes in
Cellulose acetate
Drill the pips

Holes are drilled at every pip, removing a precise amount of plastic from each face.
Fill the pips flush

Colored material of the same density as the plastic goes back into the holes, so each face weighs exactly the same as the others.

Goes in
Paint
Check size and balance

Finished dice are checked for defects and measured for dimensions, and sets are tested for balance and fair rolls.

End of the lineDice

Worth repeating

Casinos print a hidden letter or number under the paint of one pip, visible only when looking into the die at the right angle.
Dice have been found that date back to before recorded history, and some historians trace them to knucklebones.
Casinos favor transparent cellulose acetate dice because tampering is easier to see than in opaque dice.