4.1.1 General
- a. The customer shall establish a specification document in conformance with the DRD in Annex A.
- b. The manufacturer shall have a quality assurance system.
- c. The manufacturer shall verify and assure conformance during production to the technical requirements specified in this clause.
4.1.2 Raw material
- a. The raw material for threaded fasteners shall be selected in accordance with the metallic materials requirements as per ECSS‐Q‐ST‐70‐71C, if not otherwise specified in the customer specification document for threaded fasteners.
- b. Nut material shall be more ductile than bolt material. NOTE The reason is that during tightening nut threads can deflect to seat on the bolt threads.
- c. Materials for threaded fasteners shall be selected in order to avoid galling of the mating surfaces.
NOTE Galling in stainless steel fasteners can be prevented by using two different steels on the mating surfaces and by specific surface treatments.
- d. Materials for threaded fasteners shall be corrosion resistant
- e. Materials shall possess high resistance to stress‐corrosion cracking as specified in ECSS‐Q‐ST‐70‐36C.
4.1.3 Head forming
- a. Fastener heads shall be formed by hot or cold forging before heat treating.
NOTE Driving recesses and lightening holes in double hexagon design can be forged or machined.
4.1.4 Heat treatment
- a. Headed forged blanks shall be heat treated and cold worked by rolling or drawing methods in accordance with the customer specification document for threaded fasteners and the specifications in clause 4.2 of this Standard.
- b. Forged blanks belonging to the same batch shall be heat treated in one batch.
- c. The manufacturer shall re‐treat a batch which, tested as in 4.3.3, did not meet the mechanical property requirements, no more than twice (three times for Titanium alloys).
- d. If a different supplier produces the blanks, inspections and quality control shall be performed as specified in 4.4.2.1 under direct responsibility of the original blanks’ supplier. NOTE This is done in the case where the manufacturer is unable to carry out the blank fabrication as requested by the customer.
- e. Grinding of shank and head bearing surfaces of blanks to obtain roughness values as specified in 4.2.4 shall be carried out after any heat treatment.
4.1.5 Head-to-shank fillet rolling
- a. Head‐to‐shank fillet rolling shall be carried out after any heat treatment and machining processes.
- b. Cold rolling shall remove from the fillet surface any evidence of previous machining or etching process.
- c. Geometrical distortion of the fillet surface shall be within the limits specified in 4.2.3.
NOTE In fasteners having compound radii between head and shank, cold rolling can be extended to the remaining part of the fillet surface.
- d. There shall be no machining or etching of the fillet radius after rolling.
4.1.6 Threads
- a. External threads shall be formed by rolling process.
- b. Thread rolling shall be carried out on each fastener in one single continuous operation.
- c. When thread rolling on each fastener is not performed in one single continuous operation, the threaded fasteners shall be submitted to a fatigue test in accordance with 4.3.5.
- d. No evidence of machining shall be observed on the thread surface after rolling.
NOTE This applies for fasteners of large diameter, where threads can be machined oversized and subsequently rolled.
- e. Thread rolling shall be carried out after heat treatment and machining of fasteners.
- f. Unless otherwise specified in the customer specification document for threaded fasteners, a single right‐hand thread shall be obtained.
- g. The thread run‐out portion of a bolt or stud shall consist in a progressive and regular junction with the shank avoiding sharp changes in section.
- h. Thread lead and runout portions shall conform to the requirements in clause 4 of ISO 3353‐1:2002.
4.1.7 Identification marking
- a. Fasteners shall be marked by depressed characters only with character size in accordance with the customer specification document for threaded fasteners and drawings.
- b. Characters for marking fasteners shall:
- be depressed no more than 0,25 mm from the surface;
- have rounded root form;
- be impressed on the upper surface of the fastener head.
- c. Marks shall univocally identify the fastener batch and manufacturer.
- d. Safe‐life fasteners shall be identification marked separately after non‐destructive inspection.
4.1.8 Surface treatment
- a. In surface plated fasteners, surface plating shall be applied to the entire fastener surface including the threaded portion. NOTE Surface plating can cause tolerance variations.
- b. Silver plating shall not be used on titanium alloy fasteners. NOTE Silver and cadmium plating are not used because they can cause embrittlement of titanium alloys, as per requirement in ECSS‐Q‐ST‐70‐71C.
- c. Baking shall be carried out after plating. NOTE The reason is to prevent hydrogen embrittlement since electrolytic plating processes generate hydrogen.
- d. The baking temperature shall be selected such that the plating and substrate materials are not deteriorated
4.1.9 Workmanship, handling and packaging
- a. Fasteners shall be free from burrs, tool marks, scale, other surface defects and contaminants.
- b. Fasteners shall be handled and packed during storage and transportation in the following way:
- pack fasteners of the same batch in unit packages;
Figure description:
Entity: ECSS (European Cooperation for Space Standardization Text: E CSS Visual details: A parallelogram divided into two sections; a white left section containing a purple serif "E" and a purple right section containing a white serif "CSS".
- do not apply any protective lubricants or substances on fasteners unless otherwise specified in the customer specification document for threaded fasteners. NOTE This is to prevent mechanical damage and contamination (e.g. from PVC or fibreboard).
- c. Each individual package shall be univocally identified by a durable and legible external marking indicating the product denomination, quantity, batch identification, manufacturer, product conformance report as in 4.4.2.5 and date of packing.
- d. Fasteners for safe‐life applications shall be packed and stored separately.