Most of us have played at least one game on a big, boxy, coin-operated table in an arcade, restaurant, bowling alley, or bar. They seem simple enough. You feed in quarters to release the balls, and as you pocket each one it returns to the windowed enclosure to wait for the next round.
Scratch on one of those tables and the cue ball comes straight back to the head of the table instead of getting trapped with the object balls. The table is sorting that out mechanically, and the trick is simpler than it looks.
Design Basics of Coin-Operated Ball Return System
Coin-operated pool tables sort the cue ball two different ways. Older tables sorted it mechanically by size, using a cue ball built deliberately oversized or undersized so a shunt or a trap door could catch it, while newer tables sort it by sensor, either with a magnet or (rarely) an optical reader. Which method a table uses depends on the manufacturer and when it was built. The size-based methods fell out of favor because an off-standard cue ball changes the angles and physics of the game.Billiards histories put the first coin-operated table patent at 1903, at a penny a game. Documentation of how the design evolved from there is thin, but the basic ball return has clearly not changed much.
Under the table’s playing surface is a maze of ball tracks. Six sloped trenches connect the pockets to one central trench, and the ball separator sits at the lowest end of that central trench doing the actual sorting. Object balls carry on down a track to the ball trap. The cue ball gets diverted onto a different track, toward a cubby at the head of the table.
The Oversized Cue Ball
The earliest method was to use a cue ball slightly too big to pass a certain threshold. These oversized cue balls typically measure 2 ⅜ inches across, a slight step up from the standard 2 ¼-inch object balls.
A strip of metal called a ball shunt is installed at the ball separator interchange, just high enough to let the object balls pass underneath it. The cue ball hits the shunt and rolls off down its own track.
These oversized-cue-ball tables are no longer made, because the added size and weight of the cue ball affects how the game plays. It shows up worst on shots straight along the rail, where the skewed contact point exerts a slight lateral force, and on anything involving English. Plenty of them are still in service, though, in bars and recreation centers.
The Undersized Cue Ball
Going the other direction worked too. A slightly smaller cue ball was the preferred method for decades in British-style pool, or “Blackball” as it’s often called. That game is played mostly in England and Australia, on 6’ or 7’ tables, with smaller balls to begin with: usually 2 inches across.
On these British coin-op tables, the smaller cue ball (usually 1 ⅞-inch) drops through a sort of trap door and rolls to the head of the table. The object balls are too wide to fall in, so they roll straight over the opening and on into the ball trap.
These tables are rarely found in the U.S. and aren’t typically manufactured anymore, again because the smaller, lighter ball changes the game dynamics described above (only inverted). They were common enough for long enough, though, that smaller cue balls became the norm in Blackball, and many players still prefer them today.
The Magnetic Cue Ball
The most common method of cue ball separation used today involves the use of magnets. Valley, the pool table manufacturer now known as Valley-Dynamo, patented the design in the mid-1960s, and their ball-return tables have used it ever since. These tables require a specially-made cue ball with metal inside. Beyond the magnet, the materials a cue ball is made of determine how it plays, and phenolic resin behaves differently from polyester.
In most magnetic coin-op tables, the ball separator is a slightly sloped trench with two ball tracks side-by-side. As the balls enter the separator, a magnet on one side pulls the cue ball onto one track while the object balls continue down the other. Some designs use a magnetic sensor instead, triggering a deflection device the moment it detects the cue ball.
Replacing a cue ball, or buying a fresh set for a home table, is its own small decision. Our guide to the best pool balls walks through the sets worth the money.
Coin-op tables in American bars are 7-footers, which is the size most people go looking for once they decide to put a table at home. Our picks for the best 7-foot pool tables cover that size specifically, including which ones use a real slate bed.
Optical Sensors
Optical sensor systems read the cue ball’s color with a sensor inside the ball return. Its appeal was that the cue ball stayed a standard ball, so nothing about the table’s physics changed to accommodate the sorting mechanism. It’s by far the rarest of the three approaches, though, and magnets took over the market decades ago.
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