ASME B18.16M-2004 pdf – Prevailing-Torque Type Steel Metric Hex Nuts and Hex Flange Nuts.
15.1 MateriaL and Mechanical Properties
Carbon steel nuts shall conform to the requirements for Property Class 5, Property Class 9, or Property Class 10 as specified in ASTM F563M. Case hardening is not allowed for any property class.
Corrosion—resistant stainless steel nuts shall conform to the requirements of ASTM F836M.
Nonferrous metal nuts shall conform to the requirements of ASTM F467M.
The prevailing-torque element of insert design nuts may be made of a material other than steel.
15.2 Performance Requirements
15.2.1 General. All values for performance requirements given in this standard are based on the test conditions specified.
Any changes in these conditions may produce different test values which should he agreed upon prior to purchase, i.e., at time of inquiry. When changes are made to the nut finish to address specific application requirements, nuts should be tested in accordance with the test methods stated in this Standard to determine any changes in test value requirements.
15.2.2 Prevailing-Torque. The prevailing-torque developed by nuts during their first installation, or any subsequent installation or removal, shall not exceed the maximum first installation torque specified for the applicable class in Table 3 when tested as specified in Prevailing-Torque Test. in addition, the prevailing-torques developed by nuts during their first and fifth removals shall not be less than the removal torques specified in Table 3 when tested as specified in Prevailing-Torque Test.
Prevailing-torque is the torque necessary to rotate the nut on its mating externally threaded component, with the torque being measured while the nut is in motion, and with no axial load in the mating component.
15.2.3 Optional Torque-Tension. On some applications of prevailing-torque nuts, it is desirable to control the amount of developed tension when a specified range of torque has been applied, if torque-tension control is required, performance requirements shall be by agreement between purchaser and supplier utilizing the Torque-Tension Test Procedures. Examples of test clamp torque values have been included in Table 4.
16.1 Test Screws for Nut Testing
Test screws shall correspond to the size and strength level of the nut to be tested. Decarburization of the screw threads shall be within the limits defined in SAE J121M, Class 3.4H.
Threads shall conform to ASME B1.13M, Class 6g. The test screw shall have a zinc phosphate and oil finish in accordance with ASTM F1137, Grade 1, After coating, the basic thread size shall not be exceeded when confirmed with a 6h GO ring gage as defined by System 21 of ASME B1.3M. Threads of all screws M24 and smaller shall be rolled. The thread surface shall be clean, free of burrs, additional lubricant, or other contamination that might affect an accurate determination of the performance of the nut.
The test screw shall be pointed in accordance with the dimensional requirements for hex cap screws as given in ASME B18.2.3.1M. The screw length shall be such that a minimum length equivalent of four thread pitches as measured from the end of the bolt will protrude through the nut when the nut is fully seated against the test washer. The thread length shall be such that a minimum of two full threads is within the grip after the nut is fully seated. See Fig. 1.
A new test screw shall be used for testing each nut.
16.2 Test Washer
Test washers shall conform to the dimensional, metallurgical, and mechanical requirements given in Table
5. Optionally, multi-hole plates or strips may be used providing they conform to the requirements for material, hardness, hole diameter, surface texture, and plating as given in Table 5.
A new test washer shall be used for testing each nut.
16.3 Torque Measuring Device
The torque measuring device shall be capable of measuring the torque while the nut is in motion. Test results may he recorded by an analog or digital device that is capable of forming a permanent record. The measuring system shall be accurate at the point of measurement within plus or minus 2%. Test equipment may be hand held or electronic, provided that accuracy and speed restrictions as noted in Drive Tool are observed.