ISO 23886:2021 pdf download – Aerospace — Collar, threaded, self-locking — Test method for torque and preload.
1 Scope This document describes torque and preload test method for threaded collars. This test method is used to measure the locking torque, breakaway torque, torque off and preload of threaded collars. 2 Normative references There are no normative references in this document. 3  Terms  and  definitions For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https:// www .org/ obp — IEC Electropedia: available at https:// www .electropedia .org/ 3.1 locking torque highest torque value obtained in the installation direction prior to contact with the bearing surface 3.2 breakaway torque torque required to start threaded collar rotation from its installed position Note 1 to entry: The breakaway torque shall be measured after twisting off the hex portion and after removal of the preload. Note 2 to entry: The breakaway torque is for seated breakaway test only. 3.3 test bolt bolt to be used in conjunction with the collar during the test 4 General requirements 4.1 Test apparatus A torque tension test bench, torsion machine or the equivalent precision machine shall be used for the test, which shall have been calibrated within a period of 12 months prior to the test date. 4.2 Test bolt Test bolt shall be in accordance with product specification.
4.3 Test accessories The material of the collar bearing surface (see Figure A.2, item 8) shall be alloy steel; the roughness of the interface contacting with the collar shall be between Ra = 0,4 µm and Ra = 0,8 μm. The hardness shall be 50 HRC to 60 HRC. 5 Detail requirements 5.1 Test procedures a) Install the test bolt on the torsion machine; install the threaded collar finger tight against the locking element; install the threaded collar hex head into the socket adapted to the machine drive mechanism. See Figure 1. Measure the distance between the end surface of the bolt and threaded collar; then calculate the cycling number.