Bowling Terms and Glossary

Sunday, March 21, 2010
By Ted Thompson

Ambient Temperature:
Temperature of the surrounding area; same as room temperature.

Approach
The area immediately in front of the lane before the foul line measuring at least 15 feet in length and not less than the width of the lane.

Asymmetrical Core (undrilled)
A ball where the RG (radius of gyration) values of the Y (high RG) and Z(intermediate RG) axes of the ball differ by more than 5% of the total differential of the ball.

Axis migration
Path of which the axis point travels across the surface of a ball as the ball travels down the lane; this path will always have the approximate same RG measurement as the ball travels.

Axis rotation
The measurement of horizontal angle through which a ball rotates; rotation is synonymous with the amount of “side roll” a bowler has.

Axis tilt
The measurement of the vertical angle through which a ball rotates; tilt is synonymous with the amount of “spin” a bowler has.

Backend
Portion of the lane after the lane conditioner ends up until the pins.

Ball track
The area on which a ball makes contact with a lane.

Bifilar
The use of two cords or wires to support the test cradle in testing the radius of gyration of a bowling pin.

Breakpoint
The apex (peak) of the hook phase curve.

Center of gravity - CG
The imaginary point inside a body of matter where the total weight of the body is thought to be concentrated.

Coefficient of friction - COF
The ratio of the force opposing the relative motion of two surfaces and the normal force acting perpendicular opposing force. In bowling, this term usually defines the interaction between the coverstock, lane conditioner and lane.

Coefficient of restitution - COR
The ratio of the energy of two objects after impact to the energy before impact. In the case of a ball striking a pin, this is the percentage of energy transfer from the ball to the pin.

Conventional Grip
The method of drilling in which the fingers are inserted to the second knuckle.

Core
The interior of the bowling ball; depending upon the construction of the ball, the core may consist of the inner core (weight block) and/or the outer core (light filler material).

Coverstock
The exterior or outer shell of the bowling ball.

Crack
A partial break or split, slight or narrow, which appears on the surface of the ball. Also referred to as “stress fractures” which often occur around thumb or finger inserts or through the bridge area between the finger holes; a cracked bowling ball is not automatically disallowed from use in certified competition. See Fissure.

Drift
The different in location between a bowler’s starting position and ending position at the foul line.

Durometer
A device to check hardness of bowling balls and bowling pins.

Edge board
The last board on each side of a pin deck or lane.

Entry angle
This is the angle at which the bowling ball enters the pins relative to the longitude of the lane.

Equator
The High RG plane of a bowling ball in symmetrical balls.


Fissure
A crack of considerable length and depth usually occurring from some breaking or parting. If the fissure reaches the ball track at any point, it is not permitted for use in USBC certified competition as it may damage the lane surface. See
Crack.

Flare
The ball track progression due to axis migration. Flare, also known as Track Flare, is what enables the bowling ball to track over a fresh portion of the surface which increases friction between the ball and the lane.

Friction
The force which opposes the relative motion of two surfaces which are in contact with each other.

Hardness
Resistance to plastic (permanent) deformation due to a constant load from a sharp object.

Heads
This is in reference to the area from the foul line to 20 feet.

Hook Phase
Described as a curve, this is the second phase of ball motion where the ball has encountered enough friction to change direction.

Initial Installation
The first installation of a surface in a brand new center.

Intermediate differential
The difference in radius of gyration between the Y (high RG) and Z (intermediate RG) axes on the bowling ball.

Kickback
The partitions that enclose the pin deck area located on the outside of the flat gutters which are also used to support the pin setting device.

Kickback plate
A plate (3/16” max. thickness) made of USBC approved materials that is used to protect the wood kickback.

Lane and approach markings
Symmetrical graphics on the playing surface as well as any targets meeting USBC specifications.

Launch Angle
The angle in which the ball exits your hand initially at the point of release.

Mass Bias
Y axis or high RG spot on the ball. See PSA.

Midlane
Area past the heads to the end of applied lane conditioner.

Modulus of Compression
Ratio of the unit stress to unit strain within the proportioned limit of material in compression.

Mohs’ Hardness
A scale for classifying a material based on relative hardness determined by the ability of a harder material to scratch a softer one.

Moment of Inertia
Resistance to change in rotation.

Nanometer
A unit of measure used for measuring the wavelength of light. One nanometer equals 1x10-9 meters or 10 angstroms.

Particle
Any additive mixed into the coverstock to change the interaction between the bowling ball, lane conditioner and the lane.

Phenolic
A plastic-like material derived from the chemical “phenol”.

Pin (in reference to a bowling ball)
This is used to indicate where the top of the weight block is located in the ball.

Pin base flat diameter
The diameter of the base of the pin which will contact a surface when a pin is stood upright.

Pin deck
The area of the lane on which the pins are spotted.

Pitch
Angle at which holes in the bowling ball are drilled in relation to the exact center of the bowling ball.

Positive Axis Point - PAP
This is the point on a ball which the ball rotates initially upon release. A bowler’s Axis Point is unique to them and has the potential to change depending on how that bowler releases the bowling ball. The Axis Point includes both a horizontal and vertical measurement from the center of grip.

Preferred Spin Axis - PSA
The axis around which a ball will migrate to and spin around when energy is added to the bowling ball; this will always be the high RG axis of the ball. This term applies to all asymmetrical and drilled symmetrical balls.

Ra – see Surface Roughness – Ra.

Radius of gyration - RG
Measured in inches, radius of gyration is the distance from the axis of rotation at which the total mass of a body might be concentrated without changing its moment of inertia.

Refinish
To put a new protective coating on lanes or pins.

Refurbish
To renew the life of an approved bowling pin by the use of plastic coatings and Nylon reinforcing over the entire pin.

Roll Phase
The third phase of ball motion where the ball is traveling on a linear path towards the pins.

Roundness
Being such that every part of the surface or the circumference is equidistant from the center.

RS – see Surface Roughness – RS.

Runout
States how far the actual surface is permitted to vary from the dimensions implied.


Serial number
An identifying series of numbers and/or letters in order to identify a specific ball; if a serial number is no longer identifiable then a new one can be engraved in order to give it a unique identifying series.

Skid Phase
The first phase of ball motion; the ball path is in a straight line and has not encountered enough friction to begin it’s hook phase.

Slabbing
The separation of glue joints in a wood core pin or separation of materials in a synthetic lane.

Span
The distance between the thumb and finger holes on a bowling ball.

Surface Roughness – Ra
The arithmetic mean of the peak to valley distances over an evaluation distance.

Surface Roughness – RS
The arithmetic mean of peak to peak distances of the local peaks in the evaluation distance.

Sward hardness
A measurement of surface hardness.

Symmetrical Core (undrilled)
A ball where the RG (radius of gyration) values of the Y (high RG) and Z (intermediate RG) axes of the ball do not differ by more than 5% of the total differential of the ball.

Synthetic
In bowling terms, any pin or lane product not made of wood.

Tail plank
The board on the rear edge of the pin deck to protect and prolong the life of a pin deck. Technically, this is not part of the lane

Thermoplastic
A plastic material which when heated will melt but after cooling will return to a solid shape.

Total differential
The difference between the X (low RG) and Y (high RG) axes values of any bowling ball.

Traction
The friction between an object and the surface on which it moves.

Two-handed approach
Both hands are placed on the ball and are left on the ball throughout the swing until release. At the point of release, a dominant hand releases the ball thereby being a one-handed delivery. Additionally, the dominant hand is determined by the side of the body about which the ball swings.

Vent hole
Any non gripping hole that intersects with a gripping hole at any depth. Any hole intended for use as a balance hole that intersects with a gripping hole will instantly be considered a vent hole.

Void
A manufactured cavity with purposeful size, dimension and/or location within an object.

Vulcanized
Rubber that has been treated with sulfur to make it harder and stronger.


USBC portions reprinted with permission from Steve Kloempken of the USBC