ASME B18-16.6:2008 pdf download

ASME B18-16.6:2008 pdf download.Nylon Insert Locknuts (Inch Series)
11.2 Mechanical Requirements
11.2.1 Proof Load. Nuts shall withstand the proof load specified for the applicable grade and thread series in Table 2 or 3 when tested as specified in para. 12.1. 11.2.2 Hardness. Nuts shall have a hardness con- forming to the limits specified for the applicable grade in Table 5 when tested as specified in para. 12.2. 11.3 Performance Requirements 11.3.1 Prevailing-Torque. The prevailing-torque developed by nuts during their first installation, or any subsequent installation or removal, shall not exceed the maximumfirstinstallationtorquespecifiedforthe appli- cable grade in Table 2 or 3 when tested as specified in para. 12.3. In addition, minimum prevailing-torque generated by nuts during their first and fifth removals shall not be less than the respective removal torques specified for the applicable grade in Table 2 or 3.
12 TEST METHODS
12.1 Proof Load Test The test sample nut shall be assembled on a test bolt (see para. 12.1.1) or on a hardened mandrel (see para. 12.1.2) with a minimum of three threads projecting through the nut. The proof load test may be performed prior to the prevailing-torque feature being added to the nut. For referee test purposes, the hardened mandrel shall be used and the prevailing-torque feature present. The maximum prevailing-torque occurring during the assembly of the nut on the test bolt or mandrel shall be recorded. A load equal to the specified proof load for the nut, as given in Table 2 or 3, shall be applied in tension or compression through the test bolt or mandrel against the nut bearing surface in an axial direction. For referee purposes, the load shall be applied in tension. The nut shall resist this load without thread stripping or rupture. The prevailing-torque necessary to remove the nut from the test bolt or mandrel shall not exceed the maximum torque occurring during assembly.
12.2 Hardness
Test The Rockwell hardness of a sample nut shall be deter- mined on the top face of the nut. The top surface of the nut shall be prepared by grinding and removing sufficient 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 allow a hardness test to be made midway between the hex corner and the major diameter of the thread. The bearing surface of 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 sectionthrough the nutaxis withreadings taken as close as possible to the nominal major diameter of the nut thread.
12.3 Prevailing-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 hard- ened 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 sam- ple nut then assembled on the bolt or mandrel. The nut shall be advanced until a minimum of three and a maximum of five full bolt or mandrel threads protrude through the top of the nut. At that time, the maximum torque shall be 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. Tightening 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 ofthe testboltormandrel protruding through the top of the nut. The hardened washer shallbe preventedfromturningduringnuttight- ening. The nutshall thenbe backed offbythe 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 throughoutthe next360 deg ofrotation 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 firstremoval position butno clamp load shallbe 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 speci- fied 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 mini- mum torque shall notbe less than the fifthremoval value as specified in Table 2 or 3. Sufficient time shall elapse between torquing cycles to prevent overheating of the test assembly.