ASME B18.16.6-2017 pdf download

ASME B18.16.6-2017 pdf download.Prevailing Torque Locknuts(Inch Series).
At no time during the two additional installations and removals should the prevailing torque exceed the maximum, first install prevailing torque value as specified for the applicable grade and thread series in Tables 12, 13, and 14. During the third removal, the minimum torque occurring while the nut is being backed off throughout the first 360 deg of rotation shall be recorded. The minimum torque shall not be less than the third removal value as specified in Tables 12, 13, and 14. Sufficient time shall elapse between installation and removal cycles to prevent overheating of the test assembly.
The speed of installation and removal of the nut shall not exceed 30 rpm and shall be continuous and uniform.
11.4 Optional Torque-Tension Test
When torque-tension data are desired by the purchaser, refer to IFI-lOl.
11.5 Test Devices, Washers, Bolts, and Mandrels
11.5.1 Torque-Measuring Device. The torque- measuring device, handheld or automatic, shall be capable of measuring the torque while the test locknut is rotating on a test bolt. The measuring devices and/or system shall be accurate within ±2% of the device scale from 20% through 100% of the full scale. Devices should not be used in the lower 20% of their full-scale capability.
11.5.2 Load-Measuring Device. The load-measuring device used in the prevailing torque test shall be capable of measuring the actual tension induced in the test bolt as the nut is tightened. The measuring devices and/or system shall be accurate within ±5% of the device scale from 20% through 100% of the full scale. The bolt clearance hole in the backing plate behind the washer shall have the same diameter and tolerance as the test washer.
11.5.3 Test Washer. Washers or multiple-hole test strips shall be plain finished and hardened to HRC 38 minimum. The washer’s outside diameter or strip width shall be larger than the maximum across corners or flange diameter, whichever is greater, of the locknuts being tested. The inside diameter of the through hole shall conform to the inside hole diameters specified in either ASME B18.21.1, Type A, or ASTM F436 for sizes through 1 in. in diameter. Washers for sizes over 1 in. shall have an inside diameter of 108% of the nominal bolt or mandrel diameter with a ÷0.032 tolerance.
Washers and strips shall not be used for more than one test per hole on each side.
11.5.4 Test Bolt. The test bolt may be used for proof load and prevailing torque testing for all sizes.
The bolt shall have threads conforming to Class 2A tolerances as specified in ASME B1.1. Threads on all bolts 1 in. in diameter and smaller shall be produced by thread rolling. Bolt length shall he such that a minimum length equivalent to six thread pitches, as measured from the end of the bolt, will protrude through the nut when the nut is seated against the test washer. Thread length shall be such that a minimum of two full threads are ‘ithiIi the grip after the nut is seated. The bolt shall be pointed in accordance with the dimensional requirements for hex cap screws as given in ASME B18.2.1. The thread surface shall be free of burrs or other contamination that might affect an accurate determination of the prevailing torque developed by the nut.
The test bolt shall have a minimum specified tensile strength not less than the specified proof load of the nut to be tested. The test bolts shall have a zinc phosphate and oil finish according to grade D of ASTM F1137.
The bolts shall conform to the surface discontinuity requirements of ASTM F788. When test bolts less than 34 in. in diameter are used, a new bolt shall be used for testing each nut. Bolts 3 in. and larger in diameter may be reused if upon nonmagnified (except for personal corrective lenses) visual inspection, the thread does not show thread flank deformation or grooving.
11.5.5 Proof Load Testing Mandrel. Proof load testing mandrels may be used for proof load testing all nut sizes.
The threaded mandrel used for proof load testing of nuts shall have threads conforming to Class 3A tolerances as specified in ASME B1.1, except that the major diameter shall be the minimum major diameter with a plus tolerance of 0.002 in. The mandrel shall be quenched and tempered to a hardness range of HRC 45—HRC 50.
Test mandrels may be reused if upon nonmagnified (except for personal corrective lenses) visual inspection the thread flanks are not visibly deformed or grooved.
11.5.6 Prevailing Torque Testing Mandrel. Prevailing torque testing mandrels may be used for all nut sizes.
The threaded mandrel used for prevailing torque testing of nuts shall have threads conforming to Class 2A tolerances for both the pitch diameter and major diameter as specified in ASME B1.1.