Bowling ball
A bowling ball is a round ball made from rubber, urethane, plastic, reactive resin (solid, particle, or pearl) or a combination of these materials which is used in the sport of bowling. Ten-pin bowling balls generally have a set of three holes drilled in them, one each for the ring and middle finger, and one for the thumb; however, rules allow for up to five finger holes. A five-pin bowling ball has no finger holes and is smaller so that the bowler can hold the ball in the palm of their hand.
Most bowling alleys provide free balls for patrons to use, called house balls, although avid bowlers may purchase their own. These are often customized, and can feature specially sized finger holes (in the case of ten-pin balls) or monograms. Bowlers that want to bowl better should buy their own bowling ball. It is amazing how much of a difference a custom fit bowling ball will make. Most people can easily buy a bowling ball that is at least 1 to 2 pounds heavier than they used as a house ball.
Bowling balls come in a wide variety of colors, and are often either a single flat color, a swirl-like design of multiple colors, or a single color with an iridescent look. It is even possible to obtain transparent bowling balls, painted in such a way as to make it appear as though an object is inside. Some objects have included skulls, footballs, and baseballs.
Inside of the ball is a core which makes each ball do something different, these cores are dynamicaly imbalanced to cause the ball to try to stablize as it is rolling down the lane. This makes the ball roll over a different point on the surface every time it revolves and "flares" or causes multiple oil rings.
Ten-pin bowling balls
Regulation ten-pin bowling balls must weigh between 8 and 16 pounds (3.6-7.2 kg) and have a diameter of 8.5 inches (21.6 cm). Since the physical size of regulation balls is the same, while the weight may differ, lighter balls are much less dense than heavier ones. Thus, 8–10 pound balls will actually float when placed in water.
The way the finger holes are aranged on the ball surface changes the core dynamics; this will change how the bowling ball hooks down the lane.
There are three different types of bowling grips for bowling balls: conventional, finger tip, and Sarge-Easter Grip. In a conventional grip, the bowler's ring and middle fingers are placed into the ball up to the second joint, while in a finger tip grip the ring and middle finger holes are made to accept the bowler's fingers only up to the first joint. A finger tip grip requires more strength, but it allows the bowler much more control in how the ball rotates after it is released. For the players with much higher rates of revolution ("rev rates"), a Sarge-Easter Grip may be required. This is when the middle finger is drilled to finger tip depth, while the ring is drilled to the conventional depth. It allows players with high revs to change their axis tilt and allow more forward roll as to keep the ball from over hooking.
In recent years, a Michigan innovator has taken the "proper fit" of a bowling ball a step further, with the advent of Interchangeable Inserts. This inventor also paved the way for the sanctioned usage of said technology (recently introduced in a house ball program) aimed at providing optimal control of the ball—for even the beginner.
Five-pin bowling balls
Five-pin bowling balls have no finger holes and are between 4.75 to 5 inches (12.1–12.7 cm) in diameter. They weigh between 3.25 and 3.625 pounds (1.47–1.64 kg). The smaller size and lighter weight of the balls allows bowlers to hold the ball in the palm of their hand when throwing.