![Bearing up or Ballsup (5530063440)](https://upload.wikimedia.org/wikipedia/commons/7/7e/Bearing_up_or_Ballsup_%285530063440%29.jpg)
Bearing balls are special highly spherical and smooth
ball
A ball is a round object (usually spherical, but can sometimes be ovoid) with several uses. It is used in ball games, where the play of the game follows the state of the ball as it is hit, kicked or thrown by players. Balls can also be used f ...
s, most commonly used in
ball bearing
A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.
The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this ...
s, but also used as components in things like
freewheel
Freewheel mechanism
In mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft. An ov ...
mechanisms. The balls come in many different ''grades''. These grades are defined by bodies such as the
American Bearing Manufacturers Association
The American Bearing Manufacturers Association is an industry trade group that deals with all aspects of bearing (mechanical), bearing technology. It was founded in 1917 as an informal group of Manufacturing, manufacturers with the purpose of ai ...
(ABMA), a body which sets standards for the precision of bearing balls. They are manufactured in machines designed specially for the job.
In 2008, the United States produced 5.778 billion bearing balls.
Grade
Bearing balls are manufactured to a specific grade, which defines its geometric
tolerances
Engineering tolerance is the permissible limit or limits of variation in:
# a physical dimension;
# a measured value or physical property of a material, manufacturing, manufactured object, system, or service;
# other measured values (such as t ...
. The grades range from 2000 to 3, where the smaller the number the higher the precision. Grades are written "GXXXX", i.e. grade 100 would be "G100".
Lower grades also have fewer defects, such as flats, pits, soft spots, and cuts. The surface smoothness is measured in two ways:
surface roughness
Surface roughness, often shortened to roughness, is a component of surface finish (surface texture). It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. If these deviations are large, ...
and
waviness
Waviness is the measurement of the more widely spaced component of surface texture. It is a broader view of roughness because it is more strictly defined as "the irregularities whose spacing is greater than the roughness sampling length". It can ...
.
Size refers to the farthest possible distance between two points on the ball's surface, as measured by two parallel plates in contact with the surface. The starting size is the ''nominal ball diameter'', which is the
nominal
Nominal may refer to:
Linguistics and grammar
* Nominal (linguistics), one of the parts of speech
* Nominal, the adjectival form of "noun", as in "nominal agreement" (= "noun agreement")
* Nominal sentence, a sentence without a finite verb
* Nou ...
, or theoretical, ball diameter. The ball size is then determined by measuring the ''ball diameter variation'', which is the difference between the largest and smallest diameter measurement. For a given lot there is a ''lot diameter variation'', which is the difference between the
mean
There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value (magnitude and sign) of a given data set.
For a data set, the ''arithme ...
diameter of the largest ball and the smallest ball of the lot.
Sphericity, or ''deviation from spherical form'',
refers to how much the ball deviates from a true spherical form (out of roundness). This is measured by rotating a ball against a linear transducer with a gauge force of less than . The resulting
polar graph
In mathematics, the polar coordinate system is a two-dimensional coordinate system in which each point on a plane is determined by a distance from a reference point and an angle from a reference direction. The reference point (analogous to the ...
is then
circumscribe
In geometry, the circumscribed circle or circumcircle of a polygon is a circle that passes through all the vertices of the polygon. The center of this circle is called the circumcenter and its radius is called the circumradius.
Not every polyg ...
d with the smallest circle possible and the difference between this circumscribed circle and the nominal ball diameter is the variation.
Manufacture
The manufacture of bearing balls depends on the type of material the balls are being made from.
Metal
Metal
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
balls start as a
wire
Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm
A wire is a flexible strand of metal.
Wire is c ...
. The wire is
sheared to give a pellet with a volume approximately that of the ball with the desired
outer diameter (OD). This pellet is then
headed Headed may refer to:
*A headed phrase, in linguistics
* Headed notepaper
See also
*
* Head (disambiguation)
The head is the part of an animal or human that usually includes the brain, eyes, ears, nose, and mouth.
Head or Heads may also refer to: ...
into a rough spherical shape. Next, the balls are then fed into a machine that
de-flash
Flash, also known as flashing, is excess material attached to a molded, forged, or cast product, which must usually be removed. This is typically caused by leakage of the material between the two surfaces of a mold (beginning along the parting l ...
es them. The machine does this by feeding the balls between two heavy
cast iron
Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...
or
hardened steel
The term hardened steel is often used for a medium or high carbon steel that has been given heat treatment and then quenching followed by tempering. The quenching results in the formation of metastable martensite, the fraction of which is reduce ...
plates, called ''rill plates''. One of the plates is held stationary while the other rotates. The top plate has an opening to allow balls to enter and exit the rill plates. These plates have fine circumferential grooves that the balls track in. The balls are run through the machine long enough so that each ball passes through many of these grooves, which ensures each ball is the same size, even if a particular groove is out of specification. The controllable machine variables are the amount of pressure applied, the speed of the plates, and how long the balls are left in the machine.
[.]
During the operation
coolant
A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corrosio ...
is pumped between the rill plates because the high pressure between the plates and
friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
creates considerable heat. The high pressure applied to the balls also induces
cold working
In metallurgy, cold forming or cold working is any metalworking process in which metal is shaped below its recrystallization temperature, usually at the ambient temperature. Such processes are contrasted with hot working techniques like hot roll ...
, which strengthens the balls.
Sometimes the balls are then run through a ''soft
grinding
Grind is the cross-sectional shape of a blade.
Grind, grinds, or grinding may also refer to:
Grinding action
* Grinding (abrasive cutting), a method of crafting
* Grinding (dance), suggestive club dancing
* Grinding (video gaming), repetitive and ...
'' process afterward to improve precision. This is done in the same type of machine, but the rill plates are replaced with
grinding stone
Millstones or mill stones are stones used in gristmills, for grinding wheat or other grains. They are sometimes referred to as grindstones or grinding stones.
Millstones come in pairs: a convex stationary base known as the ''bedstone'' and ...
s.
[.]
If the balls are steel they are then
heat treated. After heat treatment they are
descaled to remove any residue or by-products.
The balls are then ''hard ground''. They are ground in the same type of machine as used before, but either an abrasive is introduced into coolant or the rotating plate is replaced with a very hard fine-grain
grinding wheel
Grinding wheels contains abrasive compounds for grinding and abrasive machining operations. Such wheels are also used in grinding machines.
The wheels are generally made with composite material . This consists of coarse-particle aggregate press ...
. This step can get the balls within ±. If the balls need more precision then they are
lapped
Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine.
Lapping often follows other subtractive processes with more aggressive material removal as a first step ...
, again in the same type of machine. However, this time the rill plates are made of a softer material, usually cast iron, less pressure is applied, the plate is rotated slowly. This step is what gives bearing balls their shiny appearance and can bring the balls between grades 10 and 48.
If even more precision is needed then proprietary chemical and mechanical processes are usually used.
The
inspection
An inspection is, most generally, an organized examination or formal evaluation exercise. In engineering activities inspection involves the measurements, tests, and gauges applied to certain characteristics in regard to an object or activity. ...
of bearing balls was one of the case studies in
Frederick Winslow Taylor
Frederick Winslow Taylor (March 20, 1856 – March 21, 1915) was an American mechanical engineer. He was widely known for his methods to improve industrial efficiency. He was one of the first management consultants. In 1909, Taylor summed up hi ...
's classic ''Principles of Scientific Management''.
Plastic
Plastic bearing balls are made in the same manner as described above.
Ceramic
![Zirconium dioxide ZrO2 bearing balls](https://upload.wikimedia.org/wikipedia/commons/6/68/Zirconium_dioxide_ZrO2_bearing_balls.jpg)
Ceramic bearing balls are made of
sintered
Clinker nodules produced by sintering
Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction.
Sintering happens as part of a manufacturing ...
materials that are then ground to size and shape as above. Common materials include:
silicon nitride
Silicon nitride is a chemical compound of the elements silicon and nitrogen. is the most thermodynamically stable and commercially important of the silicon nitrides, and the term "silicon nitride" commonly refers to this specific composition. It ...
() and
zirconium dioxide
Zirconium dioxide (), sometimes known as zirconia (not to be confused with zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabi ...
().
Materials
Common materials include
carbon steel
Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:
* no minimum content is specified or required for chromium, cobalt ...
,
stainless steel
Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...
,
chrome steel
Chrome steel is one of a class of non stainless steels such as AISI 52100, En31, SUJ2, 100Cr6, 100C6, DIN 5401 which are used for applications such as bearings, tools, drills and utensils.
Popular culture
The term was used in both the origina ...
,
brass
Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other with ...
,
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
,
tungsten carbide
Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
,
platinum
Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver".
Platinu ...
,
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...
,
titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
,
plastic
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
. Other less common materials include
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
,
monel
Monel is a group of alloys of nickel (from 52 to 67%) and copper, with small amounts of iron, manganese, carbon, and silicon. Monel is not a cupronickel alloy because it has less than 60% copper.
Stronger than pure nickel, Monel alloys are res ...
,
k-monel,
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
,
silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
,
glass
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...
, and
niobium
Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...
.
[.]
See also
*
Steel shot
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant t ...
References
{{DEFAULTSORT:Ball Bearing
Bearings (mechanical)
Hardware (mechanical)
Metalworking
Rolling-element bearings