For a commercial vessel, the anchor chain connects the anchor to the hull [4]. For a buyer or a technical office, the important point is that no single number describes the whole product. A line such as "stud link anchor chain" is a starting point, not a specification. A chain is built from named links and connecting parts, and it is ordered against several independent fields.
Read a proper specification as a set of fields: the construction (stud link or studless), the nominal diameter, the grade, the standard the chain is made to, the shot length and the total supplied length, and the connecting parts at each end. Whichever field is missing, the description is still incomplete. [1][4]
The rest of this article walks the chain from a single link to the finished cable, defines the terms that appear on drawings and specifications, and sets out what each field means and what to check before ordering.
Reading a chain from link to end
An anchor chain is assembled from chain-shots — chain assemblies of a given nominal length — joined by connecting parts [1]. Within a shot, the basic unit is the common link. The connection arrangement determines where enlarged and end links are needed; they should not be assumed at every joint:
- Common link — the basic link a chain-shot is built from. [1]
- Enlarged link — a strengthened link used between a common link and an end link in a D-type joining-shackle arrangement, or between a common link and a swivel. [1]
- End link — a strengthened link used at shot ends in a D-type joining-shackle arrangement, or where an outboard shot connects to an end shackle. [1]
- Joining shackle — the shackle that connects one chain-shot to the next; it can be of D-type or Kenter type. [1]
- End shackle — an enlarged shackle used to connect the outboard chain-shot to the anchor. [1]
- Swivel — a movable component of the outboard chain-shot that prevents excessive twisting of the chain cable. A swivel shackle fastened to the anchor shackle or shank has the same function. [1]
Two families of parts are being described here, and it pays to keep them apart. Common, enlarged and end links are links — they are part of the chain body itself. Joining shackles, end shackles and swivels are connecting parts — hardware fitted between bodies. A published supplier drawing of one arrangement shows a common link joined through a joining shackle, with an enlarged link and end link leading to an anchor shackle, and a swivel forerunner built as common link, enlarged link, swivel, enlarged link and end link in series [3]. That is one example of how the parts go together, not the only permitted arrangement.
The fields a chain specification has to carry
The table below lists the fields that define an anchor chain as a product, what each one actually means, and what to check against the drawing and documents.
| Specification field | What it means | What to check |
|---|---|---|
| Construction (stud link or studless) | Whether each common link carries a stud (cross-brace) or is open | Confirm the form the order and drawing actually name; the word "chain" alone does not fix it |
| Nominal diameter (d) | The design size, defined as the nominal diameter of the common link, not the link's overall length or clear opening [1] | That the size is stated as a nominal diameter measured on the common link, and referenced to a drawing |
| Grade | A grade designation that belongs to the applicable standard or rules [1] | Read the grade against the standard it comes from: labels are not automatically interchangeable between documents |
| Standard | The standard the chain is specified to; for stud-link anchor chains the shape, proportions, dimensions and tolerances of the component parts are set out in ISO 1704 [1] | Which standard, and which edition, the order is placed against |
| Shot length and total supplied length | A chain-shot is a chain assembly of a given nominal length, and a cable is built from several shots [1] | State the shot length and the total supplied length separately, so neither is assumed |
| Connecting configuration | Which connecting parts join the shots and terminate the ends (joining shackles, end shackle, swivel) [1] | That the included parts, and their positions at each end, are named rather than left as "complete chain" |
| Documents and marking | The records and marks supplied with the chain | What the file actually covers for this order — a procurement check, not an assumption that one document describes every unit |
One further check sits behind the table: component dimensions are expressed with reference to the nominal chain diameter [2]. That is a way of drawing the parts consistently; it does not by itself prove that parts of the same nominal diameter from different sources are interchangeable.
Stud link and grade are different fields
Two questions get merged that should stay separate. Stud link or studless is a question of construction — whether a link carries a stud. Grade is a separate field: a designation taken from the standard or rules the chain is supplied to. ISO 1704 defines its own grade labels for stud-link anchor chains, and supplier documents use their own labels for the grades they supply [1]. Because the labels come from different documents, a grade name should be read against the standard or rules it belongs to rather than matched across documents as if the naming were universal. The construction difference between stud link and studless, and how each is applied, is a subject in its own right and is not settled by the grade.
"Shot" and "shackle" — terms that need pinning down
Two words need a clear meaning on a chain specification.
Shot is a length term as well as a component term. A chain-shot is an assembly of common links and joining shackles with a given nominal length [1], and it is the unit by which a cable's length is built up. Do not infer the length from the word alone: state the nominal length required by the applicable standard or order.
Shackle is a hardware term. On the chain it names real parts — joining shackles, end shackles, swivel shackles. The same word is also used as a chain-length term, so the intended meaning needs to be clear. When a document says "shackle" where it means a length, the reader cannot tell whether hardware or length is meant. The safe habit is the same for both words: state the length, or name the part, and keep the supplied total length distinct from any paid-out length used for anchoring. The two are not the same figure, and a specification that leaves them blurred cannot be checked.
Common misreadings and the next step
- "Diameter describes the chain." One diameter does not fix the construction, grade, standard, lengths or connecting parts. Read the field set, not the headline number.
- "The same grade name means the same chain." Grade labels belong to the document that defines them; treat a label as scoped to its standard or rules.
- "Same nominal diameter means interchangeable parts." Dimensions are referenced to the nominal diameter for drawing consistency, not as a guarantee of interchangeability between sources [2].
- "Supplied length equals working length." The total length supplied is a product figure; the length paid out in service is a separate matter.
To move from reading a specification to checking one, gather the pieces that actually define the chain: the existing specification or drawing, the construction and nominal diameter it names, the standard and grade it is ordered against, and the connecting configuration at each end. With those in hand, review the anchor chain range, look at the connecting parts, and contact us with what you have, so the chain and its ends can be identified against your own documents rather than replaced by assumption.
References
[1] ISO 1704:2022(E), Ships and marine technology — Stud-link anchor chains, preview copy (iTeh), Clause 1 (scope) and Clauses 3.1–3.11 (terms and definitions), 4.2.1.2 (nominal diameter) and 6 (grade) (https://cdn.standards.iteh.ai/samples/77746/bf35a8e6871a4fcaabbef575f43d1dab/ISO-1704-2022.pdf). Cited for the standard's own terminology and field definitions. A third-party preview, not the complete standard; the cited clauses lie within the previewed portion.
[2] IACS, Recommendation No. 79 — Anchoring Equipment, Annex, "Anchor Chain Links — Typical Design" (https://iacs.s3.af-south-1.amazonaws.com/wp-content/uploads/2022/05/20151746/rec_79_pdf219.pdf). Cited only for the note that component dimensions are shown as multiples of the nominal diameter d of the common link. Not evidence that parts of the same nominal diameter are interchangeable.
[3] Fountom, Deck Machinery — Anchor Chain product catalogue, "Stud Link Components" (https://www.fountom.com/service_warranty/downloads/Fountom_Anchor_Chain.pdf). A supplier drawing, cited as one published example of how common, enlarged and end links, joining shackles and a swivel forerunner are assembled. Not the only standard arrangement, and not evidence of any supplier's certification or of Andy Marine's supply.
[4] Australian Maritime Safety Authority, National Standard for Commercial Vessels, Part C, Section 7, Subsection 7D (Ed.1.5, 2024), Chapter 4 (https://www.amsa.gov.au/sites/default/files/2024-10/nscv-c7d-ed-1.5-20241001.pdf). Cited only for the connection function of the anchor cable between the anchor and the vessel. Domestic-vessel guidance with a sheltered/emergency scope, not a universal rule for all ocean-going ships.
