BS 3320:1988 pdf download.Determination of slippage resistance of yarns in woven fabrics: seam method.
2 Principle A strip of fabric is folded and stitched across its width. The strip is cut at a distance from the seam line and then extended at right angles to the seam by using grab-test jaws, and the force required to cause a specified seam opening is determined.
3 Apparatus
3.1 Sewing machine, electrically operated, single needle, industrial lockstitch, capable of producing stitch type 301 described in BS 3870-1 (see Figure 1) at a speed of not more than 3 000 stitches per minute.
3.2 Needles, throat-plate and feed-dog (see clause 5).
3.3 Tensile-strength tester, complying with at least grade 2.0 of BS 1610-1 and capable of giving a rate of jaw separation of 100 ± 10 mm/min. Grab-test clamps shall be used, each clamp having one jaw face measuring 25 mm perpendicular to the application of force and not less than 25 mm or more than 50 mm in the direction parallel to the application of force. The other jaw face shall be 25 mm in the direction parallel to the application of force and not less than 25 mm in the direction perpendicular to the application of force.
NOTE 1 These sizes of jaw face give a gripped area of 25 mm ? 25 mm.
4 Conditioning and testing atmosphere The standard temperate atmosphere for testing textiles defined in BS 1051 shall be used for conditioning and testing, i.e. an atmosphere having a relative humidity of 65 ± 2 % and a temperature of 20 ± 20 ? C.
5 Adjustment of sewing machine Insert a needle of metric number 90 and the corresponding throat-plate and feed-dog and set the machine to give a stitch rating of 5.0 stitches per centimetre when sewing a piece of test fabric with the needle of the machine unthreaded. Measure the spacing of the holes thus produced. Adjust the thread tension as follows. With the lower-thread bobbin, in its case, removed from the machine, hold the thread issuing from the bobbin case so as to allow the case to run down the thread as it unwinds. Adjust the tension spring on the bobbin case so that the case runs down the thread at a slow uniform speed. Replace the bobbin in the machine and adjust the tension of the thread feed to the needle so that, when a double thickness of the fabric under test is stitched, the cross-over between the needle thread and the spool or shuttle thread is located midway between the upper and lower surfaces of the seam (see Figure 1).BS 3320 pdf download.