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| [[File:Bont High Roller G4 110mm 85A and 83A.jpg|thumb|Two [[inline skates]] wheels with different durometer - 85A and 83A.]]
| | Friends contact her Felicidad and her spouse doesn't like it at all. He presently lives in Idaho and his mothers and fathers live nearby. To play croquet is the pastime I will by no means quit performing. Interviewing is what she does.<br><br>My web page: car warranty, [http://Freebusinesscollege.com//read_blog/198199/great-ideas-about-auto-repair-that-anyone-can-use Read More Listed here], |
| <!--[[Image:Tire tread.jpg|thumb|right|300px|An automotive [[tire]] tread typically ranges from 50A to 70A, depending on the application.]]-->
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| '''Durometer''' is one of several measures of the [[hardness]] of a material. Hardness may be defined as a material's resistance to permanent indentation. The durometer scale was defined by Albert F. Shore, who developed a measurement device called a durometer in the 1920s. The term durometer is often used to refer to the measurement, as well as the instrument itself. Durometer is typically used as a measure of hardness in [[polymer]]s, [[elastomer]]s, and [[rubber]]s.<ref name="matweb">{{cite web | |
| |url=http://www.matweb.com/reference/shore-hardness.asp
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| |title=Shore (Durometer) Hardness Testing of Plastics
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| |accessdate=2006-07-22 }}</ref>
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| == Durometer scales ==
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| There are several scales of durometer, used for materials with different properties. The two most common scales, using slightly different measurement systems, are the ASTM D2240 type A and type D scales. The A scale is for softer plastics, while the D scale is for harder ones. However, the [[ASTM]] D2240-00 testing standard calls for a total of 12 scales, depending on the intended use; types A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R. Each scale results in a value between 0 and 100, with higher values indicating a harder material.<ref name="uofm">{{cite web
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| |url=http://www.calce.umd.edu/general/Facilities/Hardness_ad_.htm#3.5
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| |title=Material Hardness
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| |publisher=CALCE and the [[University of Maryland, College Park|University of Maryland]]
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| |year=2001
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| |accessdate=2006-07-22 }}</ref>
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| ==Method of measurement==
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| Durometer, like many other hardness tests, measures the depth of an indentation in the material created by a given force on a standardized presser foot. This depth is dependent on the hardness of the material, its [[viscoelasticity|viscoelastic]] properties, the shape of the presser foot, and the duration of the test. ASTM D2240 durometers allows for a measurement of the initial hardness, or the indentation hardness after a given period of time. The basic test requires applying the force in a consistent manner, without shock, and measuring the hardness (depth of the indentation). If a timed hardness is desired, force is applied for the required time and then read. The material under test should be a minimum of 6.4 mm (.25 inch) thick.<ref name="npl">{{cite web
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| |url=http://www.npl.co.uk/server.php?show=ConWebDoc.379
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| |title=Rubber Hardness
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| |publisher=[[National Physical Laboratory, UK]]
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| |year=2006
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| |accessdate=2006-07-22 }}</ref>
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| | |
| {| class="wikitable" style="text-align:center"
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| |+ Test setup for type A & D<ref name="npl"/>
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| ! Durometer || Indenting foot || Applied mass [kg] || Resulting force [N]
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| |-
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| | Type A || Hardened steel rod 1.1 mm - 1.4 mm diameter, with a truncated 35° cone, 0.79 mm diameter || 0.822 || 8.064
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| |-
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| | Type D || Hardened steel rod 1.1 mm - 1.4 mm diameter, with a 30° conical point, 0.1 mm radius tip || 4.550 || 44.64
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| |}
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| The ASTM D2240 standard recognizes twelve different durometer scales using combinations of specific spring forces and indentor configurations. These scales are properly referred to as durometer types; ''i.e.'', a durometer type is specifically designed to determine a specific scale, and the scale does not exist separately from the durometer. The table below provides details for each of these types, with the exception of Type R.<ref name="CCSi, Inc.">{{cite web|title=DuroMatters! Basic Durometer Testing Information|url=http://www.ccsi-inc.com/t-durometer-testing.pdf|publisher=CCSi, Inc.|accessdate=29 May 2011}}</ref>
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| {| class="wikitable" style="text-align:center"
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| ! Durometer Type || Configuration || Diameter || Extension || Spring force
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| |-
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| | A || 35° truncated cone ([[frustum]]) || {{convert|1.40|mm|in|abbr=on}} || {{convert|2.54|mm|in|abbr=on}} || {{convert|822|gf|N|abbr=on}}
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| |-
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| | C || 35° truncated cone (frustum) || {{convert|1.40|mm|in|abbr=on}} || {{convert|2.54|mm|in|abbr=on}} || {{convert|4536|gf|N|abbr=on}}
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| |-
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| | D || 30° cone || {{convert|1.40|mm|in|abbr=on}} || {{convert|2.54|mm|in|abbr=on}} || {{convert|4536|gf|N|abbr=on}}
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| |-
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| | B || 30° cone || {{convert|1.40|mm|in|abbr=on}} || {{convert|2.54|mm|in|abbr=on}} || {{convert|822|gf|N|abbr=on}}
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| |-
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| | M || 30° cone || {{convert|0.79|mm|in|abbr=on}} || {{convert|1.25|mm|in|abbr=on}} || {{convert|78|gf|N|abbr=on}}
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| |-
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| | E || {{convert|2.5|mm|in|abbr=on}} spherical radius || {{convert|4.50|mm|in|abbr=on}} || {{convert|2.54|mm|in|abbr=on}} || {{convert|822|gf|N|abbr=on}}
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| |-
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| | O || {{convert|1.20|mm|in|abbr=on}} spherical radius || {{convert|2.40|mm|in|abbr=on}} || {{convert|2.54|mm|in|abbr=on}} || {{convert|822|gf|N|abbr=on}}
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| |-
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| | OO || {{convert|1.20|mm|in|abbr=on}} spherical radius || {{convert|2.40|mm|in|abbr=on}} || {{convert|2.54|mm|in|abbr=on}} || {{convert|113|gf|N|abbr=on}}
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| |-
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| | DO || {{convert|1.20|mm|in|abbr=on}} spherical radius || {{convert|2.40|mm|in|abbr=on}} || {{convert|2.54|mm|in|abbr=on}} || {{convert|4536|gf|N|abbr=on}}
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| |-
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| | OOO || {{convert|6.35|mm|in|abbr=on}} spherical radius || {{convert|10.7|mm|in|abbr=on}} - {{convert|11.6|mm|in|abbr=on}} || {{convert|2.54|mm|in|abbr=on}} || {{convert|113|gf|N|abbr=on}}
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| |-
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| | OOO-S || {{convert|10.7|mm|in|abbr=on}} radius disk || {{convert|11.9|mm|in|abbr=on}} || {{convert|5.0|mm|in|abbr=on}} || {{convert|197|gf|N|abbr=on}}
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| |}
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| Note: "Type R is a designation, rather than a true "type". The R designation specifies a presser foot diameter (hence the R, for radius; obviously D could not be used) of 18 ± 0.5 mm (0.71 ± 0.02 in) in diameter, while the spring forces and indenter configurations remain unchanged. The R designation is applicable to any D2240 Type, with the exception of Type M; the R designation is expressed as Type xR, where x is the D2240 type, ''e.g.'', aR, dR, etc.; the R designation also mandates the employment of an operating stand".<ref name="CCSi, Inc."/>
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| The final value of the hardness depends on the depth of the indenter after it has been applied for 15 seconds on the material. If the indenter penetrates 2.54 mm (0.100 inch) or more into the material, the durometer is 0 for that scale. If it does not penetrate at all, then the durometer is 100 for that scale. It is for this reason that multiple scales exist. Durometer is a dimensionless quantity, and there is no simple relationship between a material's durometer in one scale, and its durometer in any other scale, or by any other hardness test.<ref name="matweb"/>
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| {| class="wikitable" style="text-align:center"
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| |+ Durometers of various common materials
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| |-
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| ! Material || Durometer || Scale
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| |-
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| | Bicycle gel seat || 15-30 || OO
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| |-
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| | [[Chewing gum]] || 20 || OO
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| |-
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| | [[Sorbothane]] || 40 || OO
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| |-
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| | [[Sorbothane]] || 30-70 || OO
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| |-
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| | [[Rubber band]] || 25 || A
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| |-
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| | Door seal || 55 || A
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| |-
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| | Automotive tire tread || 70 || A
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| |-
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| | Soft wheels of [[roller skates]] and [[skateboard]] || 78 || A
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| |-
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| | Hydraulic [[O-ring]] || 70-90 || A
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| |-
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| | Hard wheels of roller skates and skateboard || 98 || A
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| |-
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| | [[Ebonite|Ebonite rubber]] || 100 || A
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| |-
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| | Solid truck tires || 50 || D
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| |-
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| | [[Hard hat]] (typically [[high-density polyethylene|HDPE]]) || 75 || D
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| |}
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| == Relation between ASTM D2240 hardness and elastic modulus ==
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| Using linear elastic indentation hardness, a relation between the ASTM D2240 hardness and the [[Young's modulus]] for [[elastomer]]s has been derived by Gent<ref name=Gent>A.N. Gent, (1958), On the relation between indentation hardness and Young's modulus, Institution of Rubber Industry -- Transactions, 34, pp. 46–57.</ref>and by Mix and Giacomin. <ref name=Mix>A. W. Mix and A. J. Giacomin, (2011), Standardized Polymer Durometry, Journal of Testing and Evaluation, 39(4), pp. 1–10.</ref> Gent's relation has the form
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| :<math>
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| E = \cfrac{0.0981 (56 + 7.62336 S)}{0.137505 (254 - 2.54 S)}
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| </math>
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| where <math>E</math> is the Young's modulus in MPa and <math>S</math> is the ASTM D2240 type A hardness. This relation gives a value of <math> E = \infty</math> at <math>S = 100</math> but departs from experimental data for <math>S < 40 </math>. Mix and Giacomin derive comparable equations for all 12 scales that are standardized by ASTM D2240.
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| Another relation that fits the experimental data slightly better is<ref name=BS903>British Standard 903, (1950,1957), Methods of testing vulcanised rubber Part 19 (1950) and Part A7 (1957).</ref>
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| :<math>
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| S = 100~ \mathrm{erf}(3.186\times10^{-4}~ E^{1/2})
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| </math>
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| where <math>\mathrm{erf}</math> is the [[error function]] and <math>E</math> is in units of Pa.
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| A first order estimate of the relation between ASTM D2240 type D hardness and the elastic modulus for a conical indenter with a 15 degree cone is <ref name=Qi>Qi, HJ and Joyce, K. and Boyce, MC, (2003), Durometer hardness and the stress-strain behavior of elastomeric materials, Rubber Chemistry and Technology, 76(2), pp. 419-435.</ref>
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| :<math> | |
| S_D = 100 - \cfrac{20(-78.188 + \sqrt{6113.36 + 781.88 E})}{E}
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| </math>
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| where <math>S_D</math> is the ASTM D2240 type D hardness and <math>E</math> is in MPa.
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| Another linear relation between the ASTM D2240 and elastic modulus has the form:
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| :<math>\ln(E) = 0.0235 S - 0.6403 ~;~~ S = \begin{cases} S_A & \mathrm{for}~20 < S_A < 80 \\ S_D + 50 & \mathrm{for}~30 < S_D < 85 \end{cases}</math>
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| | |
| where <math>S_A</math> is the ASTM D2240 type A hardness, <math>S_D</math> is the ASTM D2240 type D hardness, and <math>E</math> is the Young's modulus in MPa.
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| ==Patents==
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| * {{US patent reference
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| | number = 1770045
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| | title = Apparatus for Measuring the Hardness of Materials
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| | inventor = A.F. Shore
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| | y = 1930 | m = 07 | d = 08
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| }}
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| * {{US patent reference
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| | number = 2421449
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| | title = Hardness Measuring Instrument
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| | inventor = J.G. Zuber
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| | y = 1947 | m = 06 | d = 03
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| }}
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| ==See also==
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| * [[Brinell hardness test]]
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| * [[Bloom (test)]]
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| * [[Hardness]]
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| * [[Knoop hardness test]]
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| * [[Leeb Rebound Hardness Test]]
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| * [[Rockwell hardness test]]
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| * [[Vickers hardness test]]
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| ==References==
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| {{reflist}}
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| ==External links==
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| *[http://www.rexgauge.com/2-uncategorised/31-reference-guide Durometer Reference Guide]
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| *[http://www.plasticsintl.com/polyhardness.htm Durometer Hardness Scale Chart]
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| *[http://www.rexgauge.com/2-uncategorised/32-comparison-chart Durometer Comparison Guide]
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| *[http://www.worldoftest.com/bareissmain.htm Durometer range]
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| * [http://www.sunray-inc.com/index.php?page=load-cap Durometer Load Capacities Chart (Polyurethane Wheels)]
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| [[Category:Dimensionless numbers]]
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| [[Category:Hardness tests]]
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| [[Category:Rubber properties]]
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