Why you should be able to read the designation

In an enquiry, specification or engineering document a chain is specified by a short code — for example, A1-3-6×19×21. It uniquely determines the link geometry and the version group. If the code is decoded incorrectly, you may get the wrong pitch or the wrong link width — and the chain will not seat in the sprocket or fit the existing assembly.

Anatomy of the designation

The general scheme: type — strength class — gauge × pitch × width.

Gauge (d) — the diameter of the round bar the link is made from, in mm. It is this (and not the outer dimension of the link) that determines strength and weight.
Pitch (t) — the internal length of the link: the distance between the inner surfaces of adjacent links.
Link width (b) — the outer width of the link: the link dimension across the chain.

Groups of our TU-001 line (class 3)

The first part of the code is a letter and a digit:

A — short-link, B — long-link;
1 — calibrated, 2 — non-calibrated.

Four groups: A1 — short-link calibrated, A2 — short-link non-calibrated, B1 — long-link calibrated, B2 — long-link non-calibrated. A calibrated chain is more precise in pitch — this matters for mechanisms where the chain runs on a sprocket.

Strength class

The second part of the code is the class: for general-purpose chains it is 3. More about classes — in the article Chain strength classes.

Designation of high-strength T8

For class 8 lifting chains the designation is different — it is set by our TU 25.93.17-002-06515248-2026: “Chain [gauge] × [pitch]-T(8)”, with the class symbol at the end. For example, Chain 8×24-T8 — gauge 8 mm, pitch 24 mm (article 8x24-T8). The link width is not part of the designation — it is a reference dimension from the TU table.

Comma in the article number, dot in the page address

Fractional sizes in article numbers are written with a comma — as is customary in Russian documentation: B2-3-2,8×35×15,6. In catalog page addresses the same size is written with a dot: /katalog/…/2.8x35. This is a URL encoding rule, not a different item.

Frequent ordering mistakes

Taking the gauge for the outer diameter of the link. No: the gauge is the rod diameter; the outer dimension of the link is noticeably larger.
Confusing the pitch and the link width. The pitch is along the chain, the width is across it. Swapping the values gives an unworkable size.
Thinking the designation sets the load. The code describes the geometry and the group; the permissible load is taken from the load table for the size.
Comparing loads from different tables directly. Different TUs have different sets of standardised fields — the comparison is incorrect without reduction.

Check yourself

Designation decoder — breaks the code down into elements and shows the table values.
Glossary — definitions of gauge, pitch, width, proof and breaking load.
Catalog: general-purpose chains to our TU 25.93.17-001-06515248-2020 and T8 lifting chains to our TU 25.93.17-002-06515248-2026.

Not sure about the designation? Send the code or a drawing — we will help you select.

How to decode a chain designation