9.6.5 Test procedureThe fastener as received shall be suitably prepared at each end, e.g. as shown in Figure 5 (detail X). For length measurements, place the fastener in a bench-mounted measuring instrument fitted with spherical anvils or any other suitable method. Gloves or tongs shall be used to minimize measurement error caused by influence of temperature. Measure the total length of the fastener before loading, lo.Mount the fastener to be tested into adaptors as shown in Figure 5. For studs, use two threaded adaptors. The length of thread engagement shall be at least 1 d. The free threaded length, lth, subjected to the load shall be 1 d.NOTE To obtain lth = 1 d in a practical way, the following procedure is proposed: first, screw on the threaded adaptor up to the thread run-out; then unscrew the adaptor by the required number of turns corresponding to lth = 1 d.The proof load, as specified in Tables 5 and 7, shall be applied axially to the fastener.The speed of testing, as determined with a free-running cross-head, shall not exceed 3 mm/min. The full proof load shall be held for 15 s.After unloading, measure the total length of the fastener, l1. 9.6.6 Test results — RequirementThe total length of the fastener after unloading, l1, shall be the same as before loading, lo, within a tolerance of ± 12,5 μm allowed for uncertainty of measurement. Some variables, such as straightness, thread alignment and uncertainty of measurement, can result in apparent elongation of the fastener when the proof load is initially applied. In such cases, the fastener shall be retested according to 9.6.5 using a 3 % greater load than the proof load specified in Tables 5 and 7 and shall be considered satisfactory if the length after the second unloading, l2, is the same as before this loading, l1, within a tolerance of ± 12,5 μm allowed for uncertainty of measurement.
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