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1 revision imported: Mitul Imported from Wikipedia

setup>Sennecaster: /* Materials */ removed copyvio tag; determined not to be original enough since it is a statistical chart

2021-03-30T16:51:52Z

Materials: removed copyvio tag; determined not to be original enough since it is a statistical chart

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{{Distinguish|Ball bearing}}
{{Globalize|article|USA|2name=the United States|date=October 2014}}
[[File:Bearing up or Ballsup (5530063440).jpg|thumb|Bearing balls]]
Bearing '''balls''' are special highly spherical and smooth [[ball]]s, most commonly used in [[ball bearing]]s, but also used as components in things like [[freewheel]] mechanisms. The balls come in many different ''grades''. These grades are defined by bodies such as the [[American Bearing Manufacturers Association]] (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.<ref>{{Citation | title = MA332Q - Antifriction Bearings | year = 2008 | publisher = [[US Census Bureau]] | url = https://www.census.gov/cir/www/332/ma332q/ma332q08.xls}}.</ref>

==Grade==
Bearing balls are manufactured to a specific grade, which defines its geometric [[tolerance (engineering)|tolerances]]. 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".<ref>Ball Definitions - The specification defines three parameters: [[surface integrity]], size, and [[sphericity]]. The surface integrity refers to surface smoothness, hardness</ref><ref name="definitions"/> Lower grades also have fewer defects, such as flats, pits, soft spots, and cuts. The surface smoothness is measured in two ways: [[surface roughness]] and [[waviness]].<ref name="definitions">{{Citation | title = ABMA Definitions | url = http://www.hooverprecision.com/html/ball_terms___definitions.html | access-date = 2009-11-16 | archive-url = https://web.archive.org/web/20091008132626/http://www.hooverprecision.com/html/ball_terms___definitions.html | archive-date = 2009-10-08 | url-status = dead }}</ref>

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 [[wikt:nominal|nominal]], 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]] diameter of the largest ball and the smallest ball of the lot.<ref name="definitions"/>

Sphericity, or ''deviation from spherical form'',<ref name="definitions"/> 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 {{convert|4|g|oz}}. The resulting [[polar graph]] is then [[circumscribe]]d with the smallest circle possible and the difference between this circumscribed circle and the nominal ball diameter is the variation.<ref name="definitions"/>

{| class="wikitable" border="1"
|+ Grade tolerances for inch sizes<ref name="definitions"/>
|-
! Grade !! Size range [in] !! Sphericity [in] !! Lot diameter variation [in] !! Nominal ball diameter tolerance [in] !! Maximum surface roughness (Ra) [μin]
|-
| 3 || 0.006–2 || 0.000003 || 0.000003 || ±0.00003 || 0.5
|-
| 5 || 0.006–6 || 0.000005 || 0.000005 || ±0.00005 || 0.8
|-
| 10 || 0.006–10 || 0.00001 || 0.00001 || ±0.0001 || 1.0
|-
| 25 || 0.006–10 || 0.000025 || 0.000025 || ±0.0001 || 2.0
|-
| 50 || 0.006–10 || 0.00005 || 0.00005 || ±0.0003 || 3.0
|-
| 100 || 0.006–10 || 0.0001 || 0.0001 || ±0.0005 || 5.0
|-
| 200 || 0.006–10 || 0.0002 || 0.0002 || ±0.001 || 8.0
|-
| 1000 || 0.006–10 || 0.001 || 0.001 || ±0.005 ||
|}

{| class="wikitable" border="1"
|+ Grade tolerances for metric sizes<ref name="definitions"/>
|-
! Grade !! Sphericity [mm] !! Lot diameter variation [mm] !! Nominal ball diameter tolerance [mm] !! Maximum surface roughness (Ra) [µm]
|-
| 3 || 0.00008 || 0.00008 || ±0.0008 || 0.012
|-
| 5 || 0.00013 || 0.00013 || ±0.0013 || 0.02
|-
| 10 || 0.00025 || 0.00025 || ±0.0013 || 0.025
|-
| 25 || 0.0006 || 0.0006 || ±0.0025 || 0.051
|-
| 50 || 0.0012 || 0.0012 || ±0.0051 || 0.076
|-
| 100 || 0.0025 || 0.0025 || ±0.0127 || 0.127
|-
| 200 || 0.005 || 0.005 || ±0.025 || 0.203
|-
| 1000 || 0.025 || 0.025 || ±0.127 ||
|}

==Manufacture==
The manufacture of bearing balls depends on the type of material the balls are being made from.

===Metal===
[[Metal]] balls start as a [[wire]]. The wire is [[shearing (metalworking)|sheared]] to give a pellet with a volume approximately that of the ball with the desired [[wikt:outer diameter|outer diameter]] (OD). This pellet is then [[heading (metalworking)|headed]] into a rough spherical shape. Next, the balls are then fed into a machine that [[de-flash]]es them. The machine does this by feeding the balls between two heavy [[cast iron]]<ref name="abbott man"/> or [[hardened steel]] 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.<ref name="hsw">{{Citation | title = How do they get the balls in ball bearings so perfectly round and smooth? | url = http://www.howstuffworks.com/question513.htm | access-date = 2009-07-01}}.</ref>

During the operation [[coolant]] is pumped between the rill plates because the high pressure between the plates and [[friction]] creates considerable heat. The high pressure applied to the balls also induces [[cold working]], which strengthens the balls.<ref name="hsw"/>

Sometimes the balls are then run through a ''soft [[Grinding (abrasive cutting)|grinding]]'' process afterward to improve precision. This is done in the same type of machine, but the rill plates are replaced with [[grinding stone]]s.<ref name="abbott man">{{Citation | title = Manufacturing | url = http://www.abbottball.com/about-abbott/today/manufacturing.php | access-date = 2009-07-02 | archive-url = https://web.archive.org/web/20090507081416/http://www.abbottball.com/about-abbott/today/manufacturing.php | archive-date = 2009-05-07 | url-status = dead }}.</ref>

If the balls are steel they are then [[heat treating|heat treated]]. After heat treatment they are [[descaling|descaled]] to remove any residue or by-products.<ref name="abbott man"/>

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]]. This step can get the balls within ±{{convert|0.0001|in|mm|abbr=on}}. If the balls need more precision then they are [[lapping|lapped]], 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.<ref name="abbott man"/><ref name="hsw"/><ref>{{Citation | title = Production Process for a standard grade 24, Chrome Steel ball | url = http://www.hooverprecision.com/html/hoover_-_ball_production_proce.html | access-date = 2009-07-02 | archive-url = https://web.archive.org/web/20080517102637/http://www.hooverprecision.com/html/hoover_-_ball_production_proce.html | archive-date = 2008-05-17 | url-status = dead }}.</ref>

If even more precision is needed then proprietary chemical and mechanical processes are usually used.<ref name="abbott man"/>

The [[inspection]] of bearing balls was one of the case studies in [[Frederick Winslow Taylor]]'s classic ''Principles of Scientific Management''.

===Plastic===
Plastic bearing balls are made in the same manner as described above.<ref name="hsw"/>

===Ceramic===
[[File:Zirconium dioxide ZrO2 bearing balls.jpg|thumb|upright=1|Zirconium dioxide ZrO2 bearing balls]]

Ceramic bearing balls are made of [[sintered]] materials that are then ground to size and shape as above. Common materials include: [[silicon nitride]] ({{chem|Si|3|N|4}}) and [[zirconium dioxide]] ({{chem|ZrO|2}}).<ref>{{Cite book | url = https://books.google.com/books?id=vR7pg0xJQ_UC&pg=PA234 | title = Handbook of space technology | isbn = 978-0-470-69739-9 | last1 = Ley | first1 = Wilfried | last2 = Wittmann | first2 = Klaus | last3 = Hallmann | first3 = Willi | date = 2009-06-16}}</ref>

==Materials==
Common materials include [[carbon steel]], [[stainless steel]], [[chrome steel]], [[brass]], [[aluminium]], [[tungsten carbide]], [[platinum]], [[gold]], [[titanium]], [[plastic]]. Other less common materials include [[copper]], [[monel]], [[k-monel]], [[lead]], [[silver]], [[glass]], and [[niobium]].<ref>{{Citation | title = Materials | url = http://www.abbottball.com/materials/ | access-date = 2009-07-03}}.</ref>

{| class="wikitable" border="1"
|+ Material comparison for common bearing balls<ref>{{Citation | title = Ball Material Types | url = http://www.hooverprecision.com/html/hoover_-_ball_material_types.html | access-date = 2010-10-06 |archive-url = https://web.archive.org/web/20080228071855/http://www.hooverprecision.com/html/hoover_-_ball_material_types.html |archive-date = 2008-02-28}}.</ref>
|-
! Material !! UNS 52100 !! Stainless steel 440C !! M50 !! BG-42 !! REX-20 !! 440NDUR !! Haynes 25 !! Si3N4 !! BECU !! 455 !! C276
|-
! Hardness [HRC]
| 60 || 58 || 62 || 62 || 66 || 60 || 50 || 70 || 40 || 50 || 40
|-
! Temperature limit [°F]
| 300 || 300 || 400 || 400 || 600 || 300 || 1200 || 1500 || 400 || 500 || 1000
|-
! Corrosion resistance<ref group=m name="table note">Where 1 is the lowest and 5 is the highest</ref>
| 1 || 3 || 1 || 2 || 1 || 4 || 5 || 5 || 1 || 4 || 5
|-
! Cost<ref group=m name="table note"/>
| 1 || 1 || 1 || 2 || 3 || 1 || 5 || 5 || 3 || 2 || 4
|-
! Availability<ref group=m name="table note"/>{{clarify|reason=Values seem to be inverted with respect to legend in footnote|date=June 2020}}
| 1 || 1 || 2 || 2 || 2 || 4 || 5 || 3 || 3 || 2 || 4
|-
! Magnetic
| Magnetic || Magnetic || Magnetic || Magnetic || Magnetic || Magnetic || Non-magnetic || Non-magnetic || Non-magnetic || Magnetic || Magnetic
|-
! Electrical Conductivity
| Conductive || Conductive || Conductive || Conductive || Conductive || Conductive || Conductive || Non-conductive || Conductive || Conductive || Conductive
|-
! Size limit
| None || None || None || None || None || None || {{convert|1.5|in|mm|abbr=on}} || No Torque Tube{{what|reason=either seems to be a cryptic way to say 'no size limit if procured from Torque Tube' or 'no size limit in application as part of a [[torque tube]]'|date=June 2020}} || None || None || {{convert|5|in|mm|abbr=on}}
|-
! Relative load capacity<ref group=m name="table note"/>
| 3 || 2 || 4 || 4 || 5 || 3 || 1 || 5 || 1 || 1 || 1
|-
! Relative fatigue life<ref group=m name="table note"/>
| 3 || 2 || 4 || 4 || 5 || 3 || 1 || 5 || 1 || 1 || 1
|}

{{reflist|group=m}}

==Seismic use==
The [[San Francisco International Airport]] building is supported by 267 columns, each of which rests on a steel ball with a diameter of {{convert|5|ft|m}}. The ball sits in a concave foundation. If an [[earthquake]] occurs, the ground can move up to {{convert|20|in|m}} in any direction, as the columns roll on their bases. This is an effective way to separate the building from the movement of the ground. After the earthquake has ended, the columns are re-centered on their bases by the force of gravity.<ref>{{cite web|url=http://science.howstuffworks.com/bearing4.htm|title=Some Interesting Uses - How Bearings Work|work=HowStuffWorks}}</ref><ref>{{cite web|url=https://www.nsf.gov/about/history/nifty50/earthquakemitigation.jsp|title=Earthquake Mitigation - Nifty 50|work=National Science Foundation}}</ref>

==See also==
* [[Steel shot]]

==References==
{{Reflist}}



{{DEFAULTSORT:Ball (Bearing)}}
[[Category:Bearings (mechanical)]]
[[Category:Hardware (mechanical)]]
[[Category:Metalworking]]
[[Category:Rolling-element bearings]]

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setup>Sennecaster: /* Materials */ removed copyvio tag; determined not to be original enough since it is a statistical chart