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1、9006379 00001/4 4bb El GENERAL MOTORS ENGINEERING STANDARDS Materials and Processes - Procedures STITCH TEAR RESISTANCE OF VINYL COATED GENUINE LEATHER GM9149P 1 SCOPE. This procedure is used to determine the stitch tear resistance of genuine leather, hand buff and full top grain (milled). 2 EQUIPME
2、NT REQUIRED. 2.1 A tensile testing machine conforming to the require- ments of the standard specifications for textile testing ma- chines, ASTM D76, shall be used. The machine shall be of the constant rate of traverse or the constant rate of extension class and shall be so operated that the pulling
3、clamps have a uniform speed of 300 f 12 mm/minute. The face of one jaw of the clamp shall measure 25 mm; that of the other jaw of this clamp, 25 x 50 mm or more. The other clamp shall be of the self-closing type with a knurled circumference. The roll shall be eccentric. 2.2 A piece of soft wire 50 +
4、 0.127 mm in diameter and 100 to 125 mm long. A good source of wire of this size is the NO. 1 Gem paper clip. A new wire shall be used for each test. 2.3 Two #23 needles as used on sewing machines in production for sewing leathers. 2.4 A 6.35 mm gauge needle holder (#223878). Available from: Singer
5、Sewing Machine Co., Southland Center, Taylor MI 48180. 2.5 A board (see Figure 1). 2.6 A 25 x 75 mm die. 3 TEST SPECIMENS. Three specimens, 25 x 75 mm, taken perpendicular, parallel or at random to backbone in the “A” area of the hide are required for the test. 4 TEST PROCEDURE. 4.1 Two holes, 1.98
6、mm dia shall be made in the specimen with the two #23 needles. The center of the holes shall be 6.35 mm from one end of the specimen, 6.35 mm apart, and equidistant from the centerline of the specimen (see Figure 1). For this drill, a press shall be used. The needle holder shall be inserted in the c
7、huck, the board is to be aligned with the two needles, one specimen inserted and the chuck lowered and the holes made. 4.2 Repeat 4.1 for the remaining specimens. 4.3 The wire shall be threaded through the holes in such a way that both ends of the wire project from one side of the specimen. 4.4 The
8、wire shall bear against the grain side. 4.5 The ends of the wire shall be placed in the self-closing clamp of the machine and the specimen in the other pair of jaws. 5 EVALUATION AND RESULTS. 5.1 The stitch tearing strength shall be reported in N. 6 GENERAL INFORMATION. This standard was revised fro
9、m FBTM 31-26 and originated by the Textiles Committee in May 1986. The latest revisions dated October 1988 and August 1986 were editorial. NOVEMBER 1988 PAGE 1 9149P 900b377 OOOOLL5 3T2 F.23 GENERAL MOTORS ENGINEERING STANDARDS 1 Materials and Processes - Procedures STITCH TEAR RESISTANCE OF VINYL COATED GENUINE LEATHER GM9149P DRILL PRESS 6.3 mm FIGURE 1 PAGE 2 NOVEMBER 1988