Like HowStuffWorks on Facebook!

How Billiard Tables Work


The Path of Least Resistance
The ball return in a commercial billiard table
The ball return in a commercial billiard table
credit

If you look inside a commercial table, there is a system of chutes that connect to the table's six pockets. Each chute is angled slightly downward from the pocket to the ball return. When a ball falls into that pocket, gravity causes it to roll along the guide until it reaches the ball return.

A pocketed ball is sent to a collection chamber where the balls line up single-file in a trough. These numbered balls remain locked in the chamber, which you can see behind a piece of Plexiglas, until someone wants to play a game and inserts some coins. By placing coins in a slot and pushing the coin arm in, you trip a lever that allows the balls to roll out of the trough into a large open access area at the foot end of the table.

A coin-slot mechanism uses a lever to open the chute, allowing the balls to fall into the access area.
A coin-slot mechanism uses a lever to open the chute, allowing the balls to fall into the access area.

Cue Balls

If a player accidentally pockets the cue ball (an act known as a scratch), the cue ball needs to come back out from the access area at the foot of the table. For the most part, coin-operated tables use two types of cue balls that can be easily separated:

  • An oversized ball that is separated by a radius gauging device.
  • A magnetic cue ball that triggers a magnetic detector.

The oversized ball is approximately 2-3/8 inches (6 cm) in diameter, which is about one-eighth of an inch (2 mm) larger than a normal ball. This slight difference in size allows the cue ball to be separated before it gets to the storage compartment. The smaller numbered balls are able to pass through a gauging mechanism, while the larger cue ball is directed through a second chute, where it falls out into an opening on the side of the table.

For players who dislike using the slightly larger cue ball, there are also coin-operated machines that can use a magnetic ball, in which a magnet is built into the core of the cue ball. Magnetic cue balls that go into a pocket are separated from numbered balls by a magnetic detector. As the magnetic ball passes this detector, the magnet triggers a deflecting device that separates the cue ball and, again, sends it into the opening on the side of the table.

The cue ball returns to a small opening at the head end of the table.
The cue ball returns to a small opening at the head end of the table.

Both the oversized and magnetic cue balls can be used interchangeably on most of today's coin-operated tables, but each has its shortcomings. If you are a beginning pool player the larger ball might not affect your play, but it can disrupt the play of some advanced players who are used to playing with the normal 2 1/4-inch diameter (5.7cm) cue ball. Likewise, some players will notice a difference in the properties of a magnetic ball, which sometimes lacks a true roll. Also, because the magnetic ball has the magnetic material inserted into it, it has a greater tendency to shatter if dropped on a hard surface.

Whether the table uses drop pockets or an automatic ball return, the components on top of the table are the same.