ANSI roller chain sizes and their ISO 606 A-series and BS/DIN B-series counterparts
Industrial roller chain is sold under two numbering systems that look interchangeable and are not. The American system numbers chains 40, 50, 60 and so on, in eighths of an inch of pitch. The British/European system numbers them 08B, 10B, 12B. ISO 606 covers both: its A series is the American chain under a metric name (ANSI 40 is ISO 08A -- the same chain), and its B series is the British chain, which shares the pitch but is a different chain, with a different roller diameter and a different inner width, needing its own sprockets. Somebody replacing chain or matching a sprocket across the two systems has to know which of those two relationships they are looking at, and no catalog states it in one place: manufacturers print an ANSI dimensional table and a separate BS/DIN dimensional table in the same document, never cross-referenced, and the pitch match has to be worked out by eye. Each record here is one ANSI chain number with its pitch, roller diameter and inner width; its ISO 606 A-series name where a publisher states one; and the BS/DIN B-series chain that shares its pitch, with that chain's own pitch, roller diameter and inner width printed alongside, so the difference is visible rather than asserted. Answers 'what is the metric equivalent of ANSI 40 chain', 'is BS 08B the same as ANSI 40', 'ANSI 40 vs 08A vs 08B', 'roller chain size conversion chart'. In scope: the ANSI sizes that the source catalog prints with a roller diameter and that have a B-series chain of the same pitch. Out of scope, and why: ANSI 25 and 35, which are rollerless -- the catalog prints a bushing diameter for them, not a roller diameter, so there is no like-for-like comparison to make; ANSI 41, which has no single-line standard dimension row in the source; and ANSI 180, whose 2 1/4 inch pitch has no B-series counterpart in the source.
The data
| ANSI chain number | ANSI pitch (in) | ANSI roller diameter (in) | ANSI width between roller link plates (in) | ISO 606 A-series number (same chain) | BS/DIN B-series chain of the same pitch | BS/DIN pitch (in) | BS/DIN roller diameter (in) | BS/DIN width between roller link plates (in) |
|---|---|---|---|---|---|---|---|---|
| 40 | 0.500 | 0.312 | 0.312 | 08A | 08B | 0.500 | 0.335 | 0.305 |
| 50 | 0.625 | 0.400 | 0.375 | 10A | 10B | 0.625 | 0.400 | 0.380 |
| 60 | 0.750 | 0.469 | 0.500 | 12A | 12B | 0.750 | 0.475 | 0.460 |
| 80 | 1.000 | 0.625 | 0.625 | 16A | 16B | 1.000 | 0.625 | 0.670 |
| 100 | 1.250 | 0.750 | 0.750 | 20A | 20B | 1.250 | 0.750 | 0.770 |
| 120 | 1.500 | 0.875 | 1.000 | 24A | 24B | 1.500 | 1.000 | 1.000 |
| 140 | 1.750 | 1.000 | 1.000 | 28B | 1.750 | 1.100 | 1.220 | |
| 160 | 2.000 | 1.125 | 1.250 | 32B | 2.000 | 1.150 | 1.220 | |
| 200 | 2.500 | 1.562 | 1.500 | 40B | 2.500 | 1.550 | 1.500 | |
| 240 | 3.000 | 1.875 | 1.875 | 48B | 3.000 | 1.900 | 1.800 |
Where this came from
Every record above links the page it was taken from and quotes the sentence that states it. These are the 2 sources this dataset was assembled from.
- ustsubaki.comhttps://www.ustsubaki.com/wp-content/uploads/tsubaki-roller-chain-catalog-compressed.pdf
- ametric.comhttps://www.ametric.com/images/document/chains-roller.pdf
Machine-readable
- data.jsonThe whole dataset — every record with its source URL and source quote.
- Open Knowledge Format bundleOne JSON object per line — every record's frontmatter and quoted span exactly as it is held here, in one fetch.
- data.csvThe same records as one flat table, for a spreadsheet or a dataframe. The last four columns are the source URL, the quoted sentence it was read from, the date we last checked it, and which columns are our reading rather than the page's words.
- How this is made and checkedWhat "verified against source" does and does not mean.
From your own code
Same records, same quotes, without scraping the page: refsource is on PyPI and npm. Each value comes back carrying the URL it was read from and the sentence on that page that states it — .source and .quote sit on the value itself rather than in a side channel, so the checking step is available instead of skipped.
pip install refsource
refsource lookup ansi-to-iso-roller-chain-cross-reference iso_a_series_number=08A
npx -y refsource lookup ansi-to-iso-roller-chain-cross-reference iso_a_series_number=08ASet your AI assistant up to use this
Two files and no account. Put this in .mcp.json at the root of your project — Claude Code, Cursor, Windsurf, VS Code and Codex all read that file — and your assistant can look this dataset up instead of recalling it. The server is remote, keyless and read-only.
{
"mcpServers": {
"referencesource": {
"type": "http",
"url": "https://referencesource.org/mcp"
}
}
}Add to Cursor · or, on the command line: claude mcp add --transport http referencesource https://referencesource.org/mcp --scope project
Then one line in the project's CLAUDE.md or AGENTS.md, so the assistant knows when to reach for it:
When a question needs "ANSI roller chain sizes and their ISO 606 A-series and BS/DIN B-series counterparts", call the referencesource MCP server at https://referencesource.org/mcp (tool `search_records`, dataset_slug `ansi-to-iso-roller-chain-cross-reference`) instead of answering from memory — every record it returns carries its source URL and a verbatim quote from that page.What each tool does, and the servers built over single registers: Connect your AI assistant.