QB/T 2540-2023Leather bracelets (English PDF)

4.1 Size and limit deviation

4.1.1 Series and limit deviation of width dimensions of bracelet shaft hole end

The width of the bracelet shaft hole end should comply with the size requirements in

GB/T 4048.The size series and limit deviation shall comply with the provisions of

Table 1.

4.1.2 Maximum deviation of bracelet length, thickness, and bracelet shaft hole

diameter

The shape of the bracelet should be straight, with a full, smooth, and natural curved surface, and a straight embedded core. The cutting and edging surfaces should be flat and smooth. The shape of the symmetrical part of the same bracelet should be basically consistent.

4.2.2 Bonding

The adhesive parts of the bracelet and hoop should be firm, flat, and free from any glue peeling.

4.2.3 Surface quality

4.2.3.1 The bracelet fabric and hoop should not have defects such as damage, wrinkles, cracks, looseness, stains, adhesive marks, etc. The color, pattern, and luster of the same bracelet should be basically consistent.

4.2.3.2 The lining of the bracelet should not have any damage, wrinkles, cracks, stains, or other obvious defects.

4.2.4 Bracelet pivot hole

The bracelet shaft hole should be smooth and unobstructed. There should be no residual glue or other foreign objects inside the hole.

4.3 Suture

4.3.1 Bracelet stitching density, stitch spacing, and limit deviation

The bracelet stitching density, stitch spacing, and limit deviation should comply with the provisions of Table 4.

4.3.2 Stitch

4.3.2.1 The stitching on the bracelet should be uniform. There should be no floating lines, open lines, jumping stitches, or other phenomena. Suture turns should be natural, smooth, and symmetrical.

4.3.2.2 The starting and ending lines of the two lines of stitching should be parallel to the end line of the shaft hole. Its parallelism should not exceed 0.5 mm.

4.3.2.3 There should be no residual threads on the surface or inside of the bracelet.

4.4 Punching holes

The punching hole surface of the bracelet should be neat and straight. The hole wall should be smooth. The deviation of the punching center from the centerline of the bracelet should not exceed 0.5 mm.

4.5 Label

The bracelet label should be clear and upright. The edge of the label should be smooth and even. The deviation of the center line of the label from the center line of the bracelet should not exceed 0.5 mm.

NOTE. If there are special requirements for the labeling position, it shall be determined through consultation between the supplier and the purchaser.

4.6 Tensile properties

The tensile performance of the bracelet shaft hole end, bracelet body, and hoop should comply with the provisions of Table 5.

4.7 Tensile and torsional fatigue resistance performance

After the tensile and torsional fatigue performance test of the bracelet, there should be no fracture or damage to the shaft hole end of the bracelet, and no fracture to the bracelet body.

4.8 Bending fatigue performance

After the bending fatigue performance test of the bracelet, there should be no peeling, breakage, cracks, or glue peeling around the bending and punching areas.

4.9 Wear resistance

After the wear resistance test, the bracelet should not show obvious discoloration, wear, or surface detachment. The felt on the test head should not show obvious staining.

4.10 Punching test

After the punching test, there should be no peeling, cracking, or glue peeling around the punched bracelet.

4.11 Buckle test

4.11.1 The bracelet should pass smoothly through the buckle without any jamming.

4.11.2 After the buckle test, bracelets with stitch buckles should not show signs of wear or surface detachment.

4.12 Light resistance performance

After the light resistance test, the surface of the bracelet should have no damage or significant color change.

4.13 Corrosion resistance

After the corrosion resistance test, the surface of the bracelet should not have bubbles, delamination, or curling.

4.14 Combination test

After the combination test, the bracelet should not exhibit phenomena such as peeling, cracking, discoloration, wrinkling, etc.

4.15 Limit of harmful substances

The limit of harmful substances in bracelets should comply with the provisions of Table

6.

The requirements, testing methods, and inspection rules for the limit of harmful substances shall be implemented in accordance with mandatory national standards if they are issued and implemented.

5.1 Instruments and equipment

The resolution and maximum allowable error of test instruments and equipment shall comply with the provisions of Table 7.

5.2 Size and limit deviation

Measure the width of the bracelet shaft hole end with a caliper. Visually inspect the number of punched holes. The punching spacing and punching aperture/width are measured using a projector. The length of the bracelet and the length of the fixed push ring extending from the end of the bracelet are measured with a steel ruler. Measure the thickness of the bracelet with a caliper at a distance of 20 mm from the end of the bracelet shaft hole. Measure the diameter of the bracelet shaft hole with a plug gauge.

During measurement, the gauge should be smoothly inserted and removed from the shaft hole without any jamming.

5.3 Appearance

Under the conditions specified in QB/T 4781, visually inspect the bracelet shape, adhesion, surface quality, and bracelet axis hole of the bracelet with normal vision.

5.4 Suture

5.4.1 Stitch length

The stitch spacing of the bracelet stitching is measured with a steel ruler.

5.4.2 Stitch mark

The stitch marks on the bracelet should be visually inspected. Parallelism can be measured with a caliper.

5.5 Punching and marking

Under the conditions specified in QB/T 4781, visually inspect with normal vision. If necessary, a caliper can be used for measurement.

5.6 Tensile properties

5.6.1 Axial hole end tension

Conduct tests on the long and short bracelets of the bracelet according to the following steps.

a) Insert a steel shaft into the bracelet shaft hole and fix the steel shaft in the upper fixture;

b) Fix the fixture at a distance of 40mm from the end of the bracelet axis hole. When fixing, the bracelet should be placed straight;

c) Set the tension value of the tension machine based on the bracelet material and conduct the test. Maintain for 10 s.

5.6.2 Carrying tension

Conduct tests on the long and short bracelets of the bracelet according to the following steps.

a) Fix the fixture 5 mm away from the end of the bracelet axis hole;

b) Fix the fixture at a distance of 40mm from the end of the bracelet axis hole;

c) Set the tension value of the tension machine based on the bracelet material and conduct the test. Maintain for 10 s.

5.6.3 Hoop tension

Thread the hoop into 2 steel shafts with a diameter of 2.5 mm and fix them in the upper and lower fixtures. Set the tension value of the tension machine based on the bracelet material and conduct the test. Maintain for 10 s.

5.7 Tensile and torsional fatigue resistance performance

Connect the bracelet to the case and buckle it into a ring shape. Place it on the tensile torque machine as shown in Figure 2.The parameter values of the testing machine are set as follows. tensile force of 50 N, torque of 0.6 N · m, twisting frequency of 60 times/min, and twisting of 1000 times.

5.8 Bending fatigue performance

Fix the two ends of the long and short bracelets respectively on the bending fatigue testing machine and conduct 2000 90° bending tests.

5.9 Wear resistance

5.9.1 Friction material

The requirements and production methods of felt shall comply with the provisions of

QB/T 2537.Dry felt is used in the dry friction test. Do not handle the felt in any way.

Wet felt is used in the wet friction test.

5.9.2 Test steps

Place the bracelet fabric facing upwards and secure it onto the friction testing machine.

Then fix the test felt on the test head so that the test felt is in horizontal contact with the bracelet. Friction back and forth along the same track (counted as one round trip). The friction area of the bracelet should avoid the punching position. The mass of the test head is (1000 ± 25) g. The stroke is 25 mm~35 mm. The frequency of exercise is (40 ±

2) times per min.

Perform a dry friction test with reciprocating friction for 300 times. Perform a wet friction test with reciprocating friction for 100 times. The dry friction test and wet friction test were conducted on different bracelets.

After the test, remove the bracelet and felt. Visually inspect the friction area of the bracelet and the condition of the felt. Wet bracelets and felt should be dried at room temperature before visual inspection.

5.10 Punching test

Choose any punching hole and insert and remove the buckle tongue used with the bracelet 200 times (counted as 1 insertion and extraction). Visually inspect the appearance of the bracelet after the test.

5.11 Buckle test

5.11.1 Thread the buckle used with the bracelet through all punching positions on the bracelet and repeat twice.

5.11.2 For bracelets using pin buckles, fix the pin buckles onto the buckle friction testing machine shown in Figure 3.Fold the bracelet through the buckle and ensure that the fabric contacts the buckle. Pull the bracelet with a force of 20 N~30 N to make it rub back and forth against the buckle (counted as one round trip). The friction stroke should be at least 2.5 cm. Friction should be repeated 200 times. The frequency of the testing machine ranges from 90 times/min~100 times/min. Visually inspect the appearance of the bracelet after the test.

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