1、Designation: D 4786 00 (Reapproved 2005)Standard Test Method forStitch Tear Strength, Single Hole1This standard is issued under the fixed designation D 4786; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method is intended for determining the
3、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 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the
4、 user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1813 Test Method for Measuring Thickness of LeatherTest SpecimenD 2209 Test Method for Tensile Strength of
5、 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 D 1813.4.2 Steel Punch, beveled on the outside, which will make a18 in. diameter h
6、ole.4.3 Metal Yoke, made to the dimension shown in Fig. 1.4.4 Steel Rod, 0.0956 0.005 in. in diameter and at least 1 in.long.4.5 Testing Machine, power-driven, as described in TestMethod D 2209.5. Test Specimen5.1 The test specimen shall be a rectangular piece of leather1 in. by 2 in. die cut from t
7、he 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 p
8、resser 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 a18 in. diameter hole
9、 on the long axis of thespecimen. The center of the hole should be532 in. 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
10、 yokeand the specimen. Clamp the free end of the specimen in theother testing machine grip. Operate the machine at 10 6 2 in.1This 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 approv
11、ed Sept. 1, 2005. Published September 2005. Originallyapproved in 1988. Last previous edition approved in 2000 as D 4786 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
12、efer to the standards Document Summary page onthe ASTM website.FIG. 1 Metal Yoke1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.per minute until the specimen starts to tear. At the instant thattearing begins, note and record the load
13、 registered by themachine.7. Calculation7.1 Calculate the pounds per in. thickness as follows:F = lb at initial tear Stitch tear strength = F/TT = thickness of sampleAvg stitch tear strength 5F/TSS = Number of individual specimens per unit test of leathers8. Report8.1 Report should include the follo
14、wing: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
15、axis of the specimen relativeto the back-bone shall be reported.9. Precision and Bias9.1 This test method is adopted from the procedures of theAmerican Leather Chemist Association where it has long beenin use and where it was approved for publication before theinclusion of precision and bias stateme
16、nts was mandated. Theoriginal interlaboratory test data is no longer available. Theuser is cautioned to verify by the use of reference materials, ifavailable, that the precision and bias of this test method isadequate for the contemplated use.10. Keywords10.1 leather; stitch tear strength; tear stre
17、ngthASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights,
18、 are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional sta
19、ndardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Com
20、mittee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 4786 00 (2005)2
