ITF

15 ii. Mass. Record the mass displayed in grams and round to one decimal place. iii. Size. Use ring gauges across at least three mutually perpendicular diameters. For all ball types, the ball shall not drop through the smaller opening by its own weight in any orientation and shall drop through the larger opening by its own weight in all orientations. Care should be taken to ensure that the ball relies only upon its own weight to pass through a ring. Record Pass/Fail. Size (Durability). The ball shall rest under its own weight directly below the contact foot of the drop gauge. A vertical load of approximately 0.5 N is applied to the ball by the contact foot. The reading is recorded 5 seconds after the load is applied. The ball diameter shall be the average of a single reading along each of three perpendicular axes, reported in centimetres to 2 decimal places. The 'Go/No-Go' method (described above) serves as the pass/fail criterion for absolute size. iv. Deformation. Test once on each axis and record the results. Report the mean value, and the maximum difference between the three readings 1 , for each ball (see also Section 1.3). The test measures the deformation of a ball under a load of 80.07 ± 0.5 N (18.00 ± 0.1 lbf) after a small initial load, of 15.57 ± 0.5 N (3.50 ± 0.1 lbf), has been applied to compress the fabric cover material. See Figure 6. The 'deformation' is measured in two senses: a. When the load is first applied (forward deformation). b. Under the action of the load prior to it being removed and after the ball has been compressed further through a total distance of 2.54 cm (1.0 inches) (return deformation). 1 The ball is placed in position so that neither platen of the machine is in contact with the cover seam. A contact load of 15.57 ± 0.5 N (3.50 ± 0.1 lbf) is applied and the displacement of the platens under this load becomes the datum for the deformation readings. A constant platen speed of 200 mm/min (7.87 inches/min) is then applied up to an additional load of 80.07 ± 0.5 N (18.00 ± 0.1 lbf). The total test load is therefore 95.64 ± 0.5 N (21.50 ± 0.1 lbf). The total test load is held for 5 seconds before the forward deformation reading is recorded. The constant platen speed is then resumed to produce a deformation of 2.54 cm (1.0 inch), and then immediately reversed until it reaches the test load (95.64 ± 0.5 N). The test load is held for 10 seconds before the return deformation is recorded. The load is then completely removed at the constant platen speed. This procedure is repeated on each ball across the two diameters at right angles to the initial position and to each other. 1 There is no specification for the maximum difference between the three readings for return deformation for stage 1 balls. (See section (iii), page 8).

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