BS ISO 23887:2021 Aerospace — Blind fasteners, threaded type, self- locking — Test method for locking torque.
This document describes the locking torque test method for blind fasteners, threaded type. This test method is used to measure the locking torque of blind fasteners with internal thread and external sleeve. It is applicable to blind fasteners consisting out of four elements (drive nut, nut, sleeve and corebolt) having a cross recess at the top of the nut.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 286-2. Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes — Part 2: Tables of standard tolerance classes and limit deviations for holes and shafts
ASM E B 107.300, Torque instrwnents (Mechanical)
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.iso.org/obp
— I EC Electroped Ia: available at https://www.electropedia.org/
blind fastener, threaded type
fastener which can be installed from only one side with an internal thread and external sleeve
Note 1 to entry: A blind [astener which can be tested with this document shall consist 01 [our elements: drive nut, nut (with a cross recess), sleeve and corebolt, see Figure 1.
torque to be measured between nut and corebolt under no axial load at disassembly process after the blind fastener is installed
4 General requirements
4.1 Test apparatus
4.1.1 Torque wrenches
Torque wrenches shall be in accordance with ASME 8107.300, Type I, Class A. Torque wrenches shall have been calibrated within 12 months prior to the test. Torque wrenches shall have an accuracy of ±4 %. The torque indicating scale of the torque wrenches shall be selected so that indicated torque readings are within 20 % and 90 % of the scale capacity. If the torque values are not within the limits, the test shall be repeated using an appropriate scale.
4.1.2 Torsion machines
Torsion machines shall have been calibrated 12 months prior to the test. Torsion machines shall have an accuracy of ±2 %. The torque indicating scale of the Torsion machine shall be selected so that indicated torque readings are within 20% and 90 % of the scale capacity. If the torque values are not within the limits, the test shall be repeated using an appropriate scale.
4.2 Test fixture
The blind fastener shall be installed on the test coupon with a specific thickness in accordance with the product specification. Installation hole size of test coupon shall be in accordance with the product specification. If the hole size is not given in the product specification the installation hole size shall be equal to the nominal fastener diameter, tolerance Hil in accordance with ISO 286-2.
A recommended test fixture is shown in Figure 2.BS ISO 23887 pdf donwload.