Don't let the pro shop terminology confuse you
The vertical angle between the axis of rotation and the surface of the lane.
The angle between the axis of rotation and the direction in which the bowling ball is traveling.
A hole drilled into a bowling ball to alter either the static or dynamic mass distribution in a bowling ball. A ball driller can use this type of hole to make a bowling ball comply with USBC specifications and/or to alter the ball dynamics to either increase or decrease hook characteristics.
The point on the lane where the ball has its strongest change in direction.
A vertical line that extends from the center of the thumb hole through the point between the finger holes.
Center of Gravity (CG)
The marking on the surface of the bowling ball about which the weight of the bowling ball is equally distributed in any direction. The true center of gravity of the bowling ball will be somewhere between this mark and the center of the ball.
The combination of velocity, loft, rev rate, axis tilt and axis rotation of the bowling ball at the moment of release.
The difference between the radius of gyration (RG) of the x-axis and the y-axis of the bowling ball. The maximum currently allowed by the USBC is 0.060.
The migration of the ball's spin axis. This is created by a combination of the layout of the ball and the dynamics of the core of the ball.
A scale used describe the total amount of hook possible from a bowling ball. The amount of hook a bowler will obtain with any given bowling ball will depend on the layout used and the bowler's delivery dynamics.
The difference between the radius of gyration of the y-axis of the ball and the z-axis. Bowling balls with asymmetric cores will have a larger intermediate differential than balls with symmetric cores.
A term indicating that the pin is 3 3/8 inches from the PAP.
The distance from the foul line that the ball impacts the lane.
A modification of the core that places the mass of the core away from the x-axis of the ball. The mass bias of a bowling ball is not always in the same location as the preferred spin axis.
A horizontal line that crosses through the center of the grip.
Pin (on a bowling ball)
The marking on the surface of the ball that indicates the location of the top of the core.
The angle at which a hole is drilled into a bowling ball.
Any of various substances added to plastics or other materials to make or keep them soft or pliable.
Positive Axis Point (PAP)
The point on the opposite side of the track that marks the axis about which the ball is spinning at the point of release.
Preferred Spin Axis (PSA)
The axis through a bowling ball that has the highest radius of gyration.
Radius of Gyration (RG)
The distance from the axis of rotation at which one could concentrate the total mass of the bowling ball without changing its rotational properties. The current USBC limits are 2.46 to 2.80.
A measurement indicating the speed at which the ball is rotating. Usually measured in revolutions per minute.
The distance between the inside edges of the gripping holes.
The surface of the ball that comes into contact with the lane. The track can be found by looking for the oil rings on the ball.
The speed and direction of the bowling ball.
Vertical Axis Line
A line perpendicular to the mid-line that crosses through the positive axis point.