5. Types of bowlers

There are two kinds of bowlers – Pace bowlers, who use the velocity of the ball to effect dismissals, and spin bowlers, who spin the ball so that it changes direction after pitching.

Pace Bowlers

Pace bowlers are often mistakenly called as fast bowlers; fast bowling really refers to only a subset of pace bowling as seen in the following table. Pace bowlers are classified according to the bowling speed at which they average in an over. The following table gives a rough idea as to the categorisation of these bowlers. 

Pace bowlers have cutters, swing, dippers and seam bowling as their bowling variation. The nomenclature for such bowlers are termed as: "Left arm fast"; "Right arm medium-fast" and so on.

Swing Bowling

Swing bowling is a technique used for bowling in the sport of cricket and is a type of pace bowling. Practitioners are known as swing bowlers. Swing bowlers make the ball curve in the air after pitching. If a bowler can make the ball swing in air after it bounces on the pitch either towards or away from the batsman he is called a seam bowler. If the ball curves into the batsman it is known as an in-swing. If it curves away from him, it is called an out-swing.

To make the ball curve, the bowler holds the ball as demonstrated.

• Swinging a cricket ball by using the correct grip

Swing is caused by two factors:

1. The raised seam of the cricket ball.
2. Asymmetry in the ball caused by uneven wear of its surface.

The ball is allowed to be made as asymmetric as possible by the constant polishing of one hemisphere of the ball by members of the fielding team, while allowing the opposite hemisphere to deteriorate through wear and tear. Over time, this produces a marked difference in the aerodynamic properties of the two sides. As a fast ball is bowled with the seam held upright and rotation about a horizontal axis, there are two possible factors that can cause the ball to move through the air.

If the seam is aligned to point slightly to one side or the other, the slipstream of air moving over the raised seam causes an aerofoil effect, pushing the ball to one side. The flow of air over the two different sides of the ball causes differential pressure based on the surface qualities of the sides. This causes the ball to curve through the air towards the rougher side. In combination, these two effects can produce considerable sideways movement of the ball through the air, known as swing.

Dippers

Dippers are a kind of swing delivery. A dipper curves into or away from the batsman before the ball pitches. The modus operandi is the same as swing, but dippers are harder to hit as they almost pitch near the batsman toes. A delivery pitched at the batsman's toes is known as a yorker. Hence dippers are often known as in-swinging yorkers or out-swinging yorkers.

Seam Bowling

Seam bowling is a type of pace bowling. Bowlers employing such a technique are known as seam bowlers or seamers. The seam joining the pieces of leather is circumferential and the stitching is distinctly raised. If the ball is bowled such that the seam hits the pitch when it bounces, this abnormality can cause the ball to deviate sideways in its path. In order to achieve this effect, a seam bowler delivers the ball with the seam held upright, holding the ball with his thumb and middle & index finger. As he releases the ball, the two fingers roll the ball backwards. This keeps the seam aligned vertically as it travels towards the batsman, making it possible for the ball to bounce on with the seam upright on the pitch. The direction and degree of deviation from a straight path are dependent on the small-scale alignment of the seam and any irregularities in the pitch surface. This means that deviation caused by seam is chaotic and unpredictable.

Often the deviation caused by seam is not large enough to cause a batsman significant problems with playing the ball. Occasionally, however, the ball can deviate far enough to hit the edge of the cricket bat instead of the middle, producing a catch for nearby fielders. Skilled batsmen have good reflexes and are less troubled by seam bowling than less proficient ones.

Cutters

Cutters are a type of delivery. Cutters are bowled by spinning the ball so that it breaks – it changes direction after pitching. A leg-cutter is a delivery that moves from the batsman's leg-side to the off-side after pitching (right to left on the TV screen). An off-cutter moves the opposite direction. Cutters are bowled at a much faster pace than the spin that spinners bowl. As a result, the deviation is not as pronounced as true spin.

Spin Bowling

Spinners are bowlers who use their wrists or fingers to spin the ball. Spinners often bowl at a much slower pace than pace bowlers at about 45 mph (~70 km/h). Due to the lack of pace on the ball, it has a longer time to grip the pitch surface and hence turns (deviates) more either to the left or right.

Top-spin or forward-spin is the forward rotation of the ball. Once the ball pitches, due to the spin imparted, the ball increases in pace. For bottom-spin or under-spin, the reverse occurs, where the ball slows down. An arm ball is bowled so that the ball comes out of the palm, resulting in the ball travelling with little or no spin.

• Deliveries in cricket and the way the ball swings

A leg-spinner is a right-handed bowler whose main delivery is the leg-break. The term leg-spin includes the leg-break as well as other surprise deliveries which consists of the flipper (under-spin), the googly (the ball moves like an off-break) and the top-spin. Similarly an off-spinner's main delivery is the off-break. Other deliveries include the doosra (leg-break), top-spin and the arm ball. 

Nomenclatures for spinners include the terms "left arm orthodox" or "right arm leg-spin" and so on. A spinner who bowls an equal amount of both wrist and finger spin is known as a mixed-bag or all-round spin.