Ball Grade Terms
Ball Diameter Variation : The difference between the largest and the smallest single diameter measurements of one ball.
Ball Grade : A specific combination of dimensional, form and surface roughness tolerances. A ball grade is designated by the grade number.
Basic Diameter : The size ordered which is the basis to which the “Diameter Tolerance” specification applies.
Basic Diameter Tolerance : The maximum allowable deviation of any ball mean diameter from the Basic Diameter, in any shipment to fill orders for that Basic Diameter.
Container Marking Increment : The standard unit steps, in millionths of an inch, used to express the Specific Diameter.
Deviation from Speherical Form : The greatest radial distance in any radial plane between a sphere circumscribed around the ball surface and any point on the ball surface.
Hardness : The measure of resistance to penetration of the ball surface or truncated flat of the ball by a specified indenting shape as determined by specified methods.
Lot : A definite quantity of balls manufactured under conditions which are presumed uniform and which is considered and identified as an entirety.
Lot Diameter Variation : The difference between the mean diameter of the largest ball and that of the smallest ball in the lot.
Nominal Ball Diameter : The diameter value which is used for the purpose of general identification of a ball size, e.g. 1/4″ 6mm, etc.
Passivation : A chemical treatment to remove corrodible surface impurities and to provide a protective film. This term is applicable to corrosion resisting balls only.
Specific Diameter : The diameter marked on the unit container, expressed in the grade’s standard marking increment nearest to the mean diameter of the balls in that container.
Surface Roughness : Surface roughness consists of all those irregularities which form surface relief and which are conventionally defined within the area where deviations of form and waviness are eliminated.
Waviness : The more widely spaced circumferential component of surface texture. (Lacking standarized practices in this field, the specifications and tolerances for waviness are subject to agreement between manufacturer and customer.)
AFBMA – Anti-Friction Bearing Manufacturers Association; An organization of bearing manufacturers with established standards for balls and bearings.
ANSI – American National Standards Institute; A private, non-profit organization that administer and coordinates the U.S. voluntary standardization and conformity assessment system.
Annealed – A metalgraphic process in which a ball is softened. An annealed ball can be ground, drilled, filed and welded. Heated to remove or prevent internal stress; free from internal stress by heating and gradually cooling; toughened or tempered.
Brinell Scale – A system of numerical notation called Brinell that measures hardness of the specific ball material as compared to the Rockwell Scale.
Burnish – To polish by friction; to make smooth and bright, especially by rubbing or friction; to brighten or make lustrous.
Burnishing – A process in which non-precision balls are used as a media to smooth or brighten parts in tumbling barrels. Burnishing media is mostly made of carbon steel.
Case Depth -A distance from the surface of the ball to the unhardened core. It is measured radially from the surface to a point where carbon content or hardness becomes the same as the core.
Chemical Certification – A form that certifies the chemical analysis of the material.
Corrosion Properties – An element that is within the chemical analysis of a specific material that can resist against corrosion (example: stainless steel alloys).
Crushing Strength – A resistance of a ball to crushing loads. It is measured in pounds as determined by the three-ball method.
Density – Mass per unit volume is measured by pounds per cubic inch.
Eddy Current Tester – A machine to safeguard the quality in final inspection and to check for surface cracks.
EDM – Electric Discharge Machining is a process that utilizes an electrode to create a hole or threads in a hardened ball.
Forge – To form by heating and hammering; to beat into shape; to make by concentrated effort.
Grade – A guaranteed sphericity expressed in millionths of an inch. For example, a grade 25 ball is spherically accurate within 25 millionths of an inch.
HFC -Headed, Flashed and Cleaned is when the ball is not put through any lapping process to make a precision tolerance. HFC balls are not hardened allowing them to be machined.
Hollow – A ball that has a space or empty cavity in the middle and is mostly used for decorative purposes or in floating applications.
ISO – International Standardization Organization – A group that sets policies and procedures for industry standards in the manufacturing of products.
MS Numbers – A Military Standard number is assigned by the Department of Defense to represent a certain size, material and tolerance of a ball.
OEM – Original Equipment Manufacturer.
Oxidize – A process in which a ball can change color or develop a surface condition due to the influence of outside contaminants; to combine chemically with oxygen; to cover with a coating of oxide of rust.
Physical Certification – A form that certifies the physical properties of the material.
Polished – A process in which a ball is put into a lapping machine and tumbled to improve the finish.
Precision – The degree of refinement with which an operation is performed or measurement stated.
Quality control – A set of procedures determined by an organization that the quality of the ball is met with certain standards.
Rockwell Hardness – A term that signifies the hardness of the ball, which is measured on various scales on a device, called a Rockwell tester.
Soft Polished – A ball that has not been heat-treated, for example a material that is already soft such as carbon.
Sphericity – Roundness which measures the difference between the largest diameter and the smallest diameter on a single ball.
Surface Waviness – A geometric irregularity of the ball surface. The wavelengths are longer than roughness.
TalyRand – An instrument that measures the roundness of the ball.
TalySurf – An instrument that checks the surface of the ball.
Tempering – A process that runs a ball for a specific length of time at a specific temperature to accomplish a specific Rockwell hardness; a substance added to modify other properties; the degree of harness and strength imparted to a metal, as by heat treatment.
Tensile Strength – Amount of pressure or psi the raw wire can withstand; the resistance of a material to longitudinal stress measured by the minimum amount of longitudinal stress required to rupture the material.
Visual Inspection – Observation of the ball surface by the naked eye. It is also called macroscopic inspection.