ASTM_D_4786_-_00_2020.pdf

Designation:D478600(Reapproved 2020)Standard Test Method forStitch Tear Strength,Single Hole1This standard is issued under the fixed designation D4786;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method is intended for determining the stitch-tearing strength of leather with a tear originating from onehole.It is particularly applicable to heavy leather.This testmethod does not apply to wet blue.1.2 The values stated in inch-pound units are to be regardedas standard.No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D1813 Test Method for Measuring Thickness of LeatherTest SpecimensD2209 Test Method for Tensile Strength of Leather3.Significance and Use3.1 This test method is intended to be used to rate leathersas to their stitch tear strengths.4.Apparatus4.1 Thickness GageA dead-mass type of thickness gage,as described in Test Method D1813.4.2 Steel Punch,beveled on the outside,which will make a18in.diameter hole.4.3 Metal Yoke,made to the dimension shown in Fig.1.4.4 Steel Rod,0.095 6 0.005 in.in diameter and at least 1in.long.4.5 Testing Machine,power-driven,as described in TestMethod D2209.5.Test Specimen5.1 The test specimen shall be a rectangular piece of leather1 in.by 2 in.die cut from the sample unit of leather.The endof the specimen in which the hole is to be punched shall be atleast 1 in.away from any uncut edge on the unit.The directionof the long axis relative to the backbone shall be noted.6.Procedure6.1 Place the specimen on the anvil of the thickness gageand lower the presser foot gently(do not drop)until it rests onthe specimen.Take the reading 5 s after the full load is reached.Read the thickness to the nearest 0.001 in.The thickness of thespecimen should be taken on the long axis near the end inwhich the hole is to be punched.6.2 Punch a18in.diameter hole on the long axis of thespecimen.The center of the hole should be532in.from the endon which the thickness was measured.6.3 Grip the yoke in one of the testing machine jaws.Placethe end of the specimen containing the hole between the armsof the yoke and pass the steel rod through the holes in the yokeand the specimen.Clamp the free end of the specimen in theother testing machine grip.Operate the machine at 10 6 2 in.per minute until the specimen starts to tear.At the instant thattearing begins,note and record the load registered by themachine.7.Calculation7.1 Calculate the pounds per in.thickness as follows:F=lb at initial tearStitch tear strength=F/TT=thickness of sampleAvg stitch tear strength5F/TSS=Number of individual specimens per unit test of leathers1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.01 on Vegetable Leather.Current edition approved Dec.1,2020.Published December 2020.Originallyapproved in 1988.Last previous edition approved in 2016 as D4786 00(2016).DOI:10.1520/D4786-00R20.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.18.Report8.1 Report should include the following:8.1.1 Stitch tear strength of each test specimen and averagestitch tear strength per unit of leather.8.1.2 The thickness measurements of all the specimenstested shall be averaged to the nearest 0.001 in.and reported asthe thickness of the sample unit of leather.8.1.3 The direction of the long axis of the specimen relativeto the back-bone shall be reported.9.Precision and Bias9.1 This t