ASME B18.16.6-2008 pdf free download.Nylon Insert Locknuts (Inch Series).
12.1.1 Test Bait. The bolt used for proof load testing .i nut shall have threads conforming to Clas. 2A tolerances as specified in ASME 111.1. The test bolt shall have a yield strength in excess of the specified proof load of the nut being tested.
12.1.2 Hardened Mandrel The hardened mandrel used for proof load testing a nut shall have threads conforming to Class 3A tolerances as specified in ASMF Bl.1, except that the major diameter shall be the minimum major diameter with a plus tolerance of 0.002 in. The mandrel shall be heat treated to a hardness of Rockwell C45 to C50.
12.2 Hardness Test
The Rockwell hardness of a sample nut shall be determined on the top face of the nut. The top surface of the nut shall be prepared by grinding and removing sultic,ent material from the top to eliminate the effects of plating. coating, or other surface conditions. Material removal shall also be such as to provide a flat area large enough to .illow a hardness test to be made midway between the hex corner and the major diameter of the thread. The bearing surface ci the nut shall be prepared parallel to the test surface with removal of plating or coating. Further preparation of the test specimen and the method of performing the test shall conform to
ASTM E 18.
For referee purposes, nut hardness shall be taken on a longitudinal section through the nut axis with readings taken as close as possible to the nominal major diameter of the nut thread.
12.3 Prevelung.Torque Test
The prevailing-torque test shall be conducted at room temperature using a load measuring device (see para. 12.3.2). A test bolt (see para. 12.3.3) and/or hardened mandrel (see para. 12.1.2) shall be inserted in the load measuring device, and hardened washer (see para. 12.3.4) placed on the bolt or mandrel and the sample nut then assembled on the bolt or mandrel. The nut shall be advanced until a minimum of three and a maximum ci five full bolt or mandrel threads protrude through the top of the nut. At that time, the maximum torque shall he recorded. This torque shall not exceed the first installed prevailing-torque value as specified for the applicable grade and thread series in Table 2 or 3. The torque measuring device shall be in accordance with para. 12.3.1.
lightening shall be continued until the nut Is seated against the hardened washer. The length of the test bolt or mandrel should be such that seating of the nut shall occur at or before a length equivalent to a maximum of nine thread pitches of the test bolt or mandrel protruding through the top of the nut, as measured from the end of the bolt or mandrel. The nut shall then be tightened until a tensile load equal to the clamp load, as specified for the applicable grade and thread series in Table 2 or 3 is developed in the bolt or mandrel. The hardened washer shall be prevented from turning during nut tightening. The nut shall then be backed off by the application of reverse torque until the tensile load in the bolt or mandrel has been reduced to zero. The lowest numerical torque occurring while the nut is being backed off throughout the nest 360 deg of rotation shall be recorded as the minimum first removal torque. This minimum torque shall not be less than the first removal prevailing- torque value as specified in Table 2 or 3. The nut shall then be backed off until the prevailing-torque element Is disengaged from the bolt or mandrel thread. The nut shall be reassembled and removed four more times. On each reassembly, the nut shall be assembled to the initial first removal position but no clamp load shall be induced in the bolt or mandrel. The test washer shall not be removed during these additional cycles.
At no time during the four 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 Table 2 or 3. During the fifth 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 fifth removal value as specified in Table 2 ni 3. Sufficient time shall elapse between torquing cycles to prevent overheating of the test assembly.
The speed of installation and removal of the nut shall not exceed 30rpm and shall be continuous and uniform.