BS 3320:1988 pdf free download.Method for Determination of slippage resistance of yarns in woven fabrics seam method.
1 Scope
BS 3320 describes a method for determination of yarn slippage in woven fabrics at stitched seams.
The method is particularly applicable to apparel fabrics, but it is not intended for industrial fabrics,
e.g. beltings.
Tests are normally made with a seam opening of 6 mm, but provision is made for a very small seam opening of 3 mm which would produce an unsatisfactory appearance on certain fabrics, e.g. fabrics with warp and weft of contrasting colours.
NOTE The titles of the publications referred to in this standard are listed on the inside back cover.
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/mm. 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 x 25 mm.
The jaws shall be capable of holding the specimen without allowing it to slip and designed so that they do not cut or otherwise weaken the specimen. The faces of the jaws shall be smooth and flat, except that when, even with packing, the test specimen cannot be held satisfactorily with flat-faced jaws, engraved or corrugated jaws shall be used.
NOTE 2 Suitable packing materials for use with either smooth or corrugated jaws include paper. felt, leather, plastics or rubber sheet.
The tensile-strength tester shall be provided with either an autographic force/extension chart recorder or an interface computer.
3.4 Means for conditioning, providing the atmosphere for conditioning and testing specified in clause 4.
3.5 Sewing thread’), white 100 % polyester core spun, commercially available ticket number 80 (approximately 440 dtex to 480 dtex), having a continuous filament polyester core and a staple polyester fibre sheath.
The sewing thread shall have a maximum extension at break of 20 % when measured in accordance with
BS 1932-1.
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 of2O±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).
6 Preparation of test specimens
6.1 Cutting
6.1.1 For slippage resistance at warpway seams prepare five specimens each 100 mm wide in the warp direction and 350 mm long in the weft direction. For slippage resistance at weftway seams prepare five specimens each 100 mm wide in the weft direction and 350 mm long in the warp direction.
6.1.2 Cut all specimens randomly from the sample avoiding fabric within 50 mm of the selvedges. Make a fold in each specimen 100 mm from one end and parallel to the 100 mm side. Make a lockstitch seam using sewing thread complying with ticket number 80 of BS 4134, in a metric size 90 needle at a rate of 5.0 stitches per centimetre at a distance of 20 mm from the fold line.
6.1.3 Cut each seamed specimen. by cutting through both layers of the fabric, 12 mm from the seam line (see Figure 2).
6.1.4 Cut each specimen in half, parallel to the seam. In this way two test specimens of equal length are produced, one with a lockstitch seam, the other without a lockstitch seam.
6.2 Conditioning
Condition the specimen in the atmosphere specified in clause 4.
7 Procedure
7.1 Select the appropriate force range so that the expected seam slippage force lies between 25 % and 80 % of the scale force chosen (this may require the testing of a preliminary test specimen in order to determine the correct range). Set the chart/crosshead ratio at 5: 1, unless using an interface computer.
7.2 Set the clamps of the tensile-strength tester a distance of 75 mm apart.
Set the tensile-strength tester to give a rate of jaw separation of 100 ± 10 mm/mm.
Clamp the unsea med test specimen in the jaws so that the test specimen is mounted centrally and produce a force/extension curve on the chart until a force of 200 N is exceeded.
Clamp the seamed test specimen in the jaws in the same way as above, ensuring the seam is midway between and parallel to the jaws and produce another force/extension curve from the same zero point on the chart.
Repeat this procedure with the remaining test specimens so that separate pairs of curves are produced. These will be used to calculate the amount of fabric slippage in the sample.
8 Calculation and expression of results For each pair of curves, measure the distance (1) to the nearest 0.5 mm between the curve without a seam and the curve with a seam at a force of 5 N. This is to compensate for initial straightening of the seamed test specimen.
Add the distance (1) to 30 mm (equivalent to a seam opening of 6 mm) but for fabrics where a seam opening of 3 mm would produce an unsatisfactory appearance, add the distance (1) to 15 mm.
Find the point on each pair of curves where the separation between them, parallel to the extension axis, is the figure calculated above (i.e. seam opening plus compensation).
Read off the force in newtons to the nearest newton at this separation. Report the average of the results to the nearest newton.
If the required separation between the curves is not achieved at or before a force of 200 N report the result as “more than 200 N”.
If the fabric tears at a force of 200 N or less and the horizontal separation cannot be found, report the result as “fabric breakdown” and quote the force at which this occurred.
9 Test report
The test report shall include the following particulars:
a) the number and date of this British Standard.
i.e. BS 3320: l 988;
b) the type of sewing thread used;
c) the average seam opening force (in newtons) and the seam opening of 6 mm or 3 mm;
d) if applicable, a statement “more than 200 N” or “fabric breakdown” and the force at which this occurred.