97 records

What thread and size is this pipe fitting?

Across 97 records covering 47 nominal sizes, threads per inch (TPI) runs from 8 (10 nominal sizes) to 28 (7 nominal sizes), and 11 is the most common — 44 of them. Every value is transcribed from the source that states it and carries the sentence it was taken from: 8 sources across 7 sites, last checked 2026-08-12, due for re-check by 2028-08-11. Every record is listed below, each linking the page its value came from.

21 records where two or more sources state different values. Both sides are reproduced on the record page, each with its own source and quote.

About this data

Dimensional specifications for NPT and BSP pipe thread sizes used in plumbing, hydraulic, and gas fittings worldwide. For each nominal pipe size within each standard, gives threads per inch, pitch, major diameter, and minor diameter — the numbers needed to identify an unknown thread or confirm whether two fittings will mate. Combines American (ASME B1.20.1) and British/ISO (ISO 228, ISO 7) standards in one table so the critical differences are visible side by side.

The data

Where this came from

Every record above links the page it was taken from and quotes the sentence that states it. These are the 8 sources this dataset was assembled from.

• machiningdoctor.comhttps://www.machiningdoctor.com/charts/bsp/
• en.wikipedia.orghttps://en.wikipedia.org/wiki/National_pipe_thread
• lsengineers.co.ukhttps://www.lsengineers.co.uk/advice-centre/bsp-thread-sizes-explained
• amesweb.infohttps://amesweb.info/Screws/BSP-Thread-Chart.aspx
• en.wikipedia.orghttps://en.wikipedia.org/wiki/British_Standard_Pipe
• geminivalve.comhttps://www.geminivalve.com/bsp-thread-vs-npt-fitting/
• htsspares.comhttps://www.htsspares.com/blog/how-to/how-to-measure-your-bsp-fittings
• trimantec.comhttps://trimantec.com/blogs/t/thread-identification-guide

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 plumbing-fitting-thread-standards thread_standard=BSP

npx -y refsource lookup plumbing-fitting-thread-standards thread_standard=BSP

Set 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 "Plumbing fitting and pipe thread standards", call the referencesource MCP server at https://referencesource.org/mcp (tool `search_records`, dataset_slug `plumbing-fitting-thread-standards`) 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.

97 records. last verified against source 2026-08-12. due for re-check by 2028-08-11.

Licence. factual compilation of thread dimensions from public reference sources; facts cited with attributed quotes, no standard document reproduced