SIST EN 3729:2008

SIST EN 3729:2008 is a SIST standard identical to EN 3729:2008 for aerospace threaded, self-locking rings with left-hand thread in FE-PA92HT (A286), silver plated. It specifies the form, dimensions, material, surface treatment, designation and marking for parts chiefly used to locate bearing outer rings axially. It is aimed at aerospace designers, manufacturers and inspectors who need a defined ring for controlled assembly and acceptance.

What does SIST EN 3729:2008 specify?

SIST EN 3729:2008 specifies one family of aerospace threaded rings and the rules needed to make, identify and check them. The standard is organized into clauses on scope, normative references, required characteristics, designation, marking and technical specification.

Clause 1 sets the application: these are threaded, self-locking, left-hand threaded rings in FE-PA92HT, silver plated, with a maximum test temperature of 450 °C. A note adds that the parts are designed to be used with 4H6H internal threads, which matters when matching the ring to the mating component.

What are the key requirements of SIST EN 3729:2008?

SIST EN 3729:2008 gives the essential requirements in Clause 3 and the identification rules in Clauses 4 to 6.

• Clause 3.1 - Configuration, dimensions, tolerances and masses: Figure 1 and Table 1 define the geometry, size codes and approximate masses, and the dimensions apply after silver plating. In practice, you use the drawing and table to select the right size and to check whether a delivered part fits the intended envelope.
• Clause 3.2 - Material: the rings are made from EN 2171 material. This tells the buyer and supplier which heat resisting steel basis is acceptable.
• Clause 3.3 - Surface treatment: EN 2786 applies, with silver plating of at least 5 µm at the pitch diameter of the threads and 5 µm to 15 µm on the other surfaces. That matters because plating thickness affects fit, wear and corrosion protection.
• Clause 3.3 - Edge condition: sharp edges are to be removed within the stated range. This reduces burrs and damage during assembly.
• Figure 1 note: the detailed form and the self-locking feature are left to the manufacturer's discretion. In practice, the document fixes the functional envelope while allowing the maker to choose the internal locking solution.
• Clause 4 - Designation: the designation combines a description block and an identity block, with a thread code from Table 1; the note allows code I9005 if needed. This gives purchasers a standard way to order the exact ring size.
• Clause 5 - Marking: marking follows EN 2424, style A, as shown in Figure 1. This supports traceability and consistent identification.
• Clause 6 - Technical specification: the rings are covered by EN 3299. That means acceptance and broader technical conditions are not limited to this dimensional document alone.

What terms does SIST EN 3729:2008 define?

SIST EN 3729:2008 uses several terms in a fixed technical sense.

• Left-hand thread: a thread that tightens in the opposite direction to a right-hand thread, used here for a deliberate assembly orientation.
• Self-locking ring: a ring designed to resist loosening after installation, which is important where vibration or load changes are expected.
• Pitch diameter: the thread diameter used as the control point for plating thickness in Clause 3.3.
• MJ thread: the aerospace metric thread form named in Table 1 and linked to ISO 5855-1.
• Designation: the ordered code used to identify the part size and type for procurement and records.
• Marking style A: the marking method referenced from EN 2424 for product identification.

Who uses SIST EN 3729:2008?

SIST EN 3729:2008 is used by aerospace fastener manufacturers, design engineers, procurement teams and quality inspectors. Designers use it to choose a ring that matches the mating internal thread and the bearing location task. Buyers and quality managers use it to specify material, plating, marking and acceptance criteria in contracts and inspection plans. Inspectors use it to verify dimensions, plating thickness and identification.

Which standards are used with SIST EN 3729:2008?

SIST EN 3729:2008 depends on several referenced standards:

• EN 2171 - gives the heat resisting steel FE-PA92-HT basis for the material.
• EN 2424 - defines aerospace product marking.
• EN 2786 - specifies electrolytic silver plating of fasteners.
• EN 3299 - provides the technical specification for self-locking shaft-nuts and threaded rings.
• EN 4317 and EN 4318 - are named as newer references related to the material designation in EN 2171.
• ISO 5855-1 - gives general requirements for MJ threads.

What does the SIST EN 3729:2008 document contain?

SIST EN 3729:2008 contains a dimensional drawing in Figure 1, a size and mass table in Table 1, and a designation example in Clause 4. The figure identifies the thread, pitch diameter, slot for left-hand thread indication, scallops and edge treatment. Table 1 lists the available thread codes and the associated MJ or MJS sizes. The document also states the marking style and points to EN 3299 for the technical specification used in procurement and acceptance.