# drawmath

Metric and imperial values on a technical drawing, converted
with the factors and rounding a shop actually uses — locally,
with no network call and nothing to configure.

Give drawmath one value, one printed callout, or one thread
designation and it answers in the other system: lengths and
GD&T values, ± tolerances, diameters with their fit class,
surface roughness, weights and threads. Each answer carries
the exact converted value alongside the rounded display
value, says how it was derived (`exact`, `rounded`, `table`
or `nearest`), and gives a confidence score.

## Precision

- Factors are the international definitions: 25.4 mm per
  inch and 0.45359237 kg per pound.
- Display values follow shop-floor convention: a 0.01 mm
  step becomes a 4-decimal inch value.
- Worked examples: `84±0.1` mm becomes `3.3071±0.0039` in,
  `Ø30 H7` becomes `Ø1.1811 H7`, `Ø40 H7` becomes
  `Ø1.5748 H7`, and Ra 1.6 µm becomes Ra 63 µin.
- Threads are matched against a metric/UNC chart covering
  M2–M30, snapped by major diameter when there is no exact
  counterpart: `M8` becomes `5/16-18 UNC`, `M6` becomes
  `1/4-20 UNC`, and `1/4-20 UNC` becomes `M6`. A matched
  thread is a nearest standard, never an interchangeable
  one — every thread result says so explicitly.

## Tools

This is a labelled subset of the original five-tool
surface. Three tools are built:

- `convert_value` — one value: `value` (for example
  `"84±0.1 mm"`, `"Ø30 H7"`, `"Ra 1.6"`, `"2.5 kg"` or
  `"M8"`), with an optional `kind` (`length`, `tolerance`,
  `gdt`, `roughness`, `weight`, `thread` or `auto`) and an
  optional `direction` (`metric_to_imperial`,
  `imperial_to_metric` or `auto`). The result JSON gives
  exact and display values, the derivation method and a
  confidence score.
- `convert_text` — a whole callout string: `text`, with an
  optional `direction`. Notation is preserved — symbols,
  fit classes and multipliers stay where they were — and
  angles are left untouched.
- `lookup_thread` — a thread cross-reference: give a
  `designation` such as `"M8"` or `"1/4-20 UNC"` for its
  chart row and nearest counterpart in the other system,
  or omit it for the full M2–M30 chart.

Two original tools are **omitted** from this subset:
`extract_drawing_text` and `convert_drawing_pdf`. They
depend on a PDF text-extraction and stamping engine that
cannot be reproduced from the published specification,
and this build carries no PDF library. The original's
`convert-drawing` prompt is likewise out of scope, as
prompts sit outside this program's tool parity scope.

Argument shapes are labelled reconstructions: the
published material pins behaviour and worked examples, not
parameter tables, so each tool takes the primary string
its behaviour implies plus the optional direction or kind
that behaviour calls for.

## CLI

```bash
npx @reneturcios/drawmath convert_value '{"value":"84±0.1 mm"}'
npx @reneturcios/drawmath convert_text '{"text":"Ø30 H7"}'
npx @reneturcios/drawmath lookup_thread '{"designation":"M8"}'
npx @reneturcios/drawmath lookup_thread '{}'
npx @reneturcios/drawmath --version
```

Exit codes: `0` on success, `1` on a runtime error, `2` on
a usage error.

## MCP server

```bash
npx -y @reneturcios/drawmath mcp
```

MCP client config:

```json
{
  "mcpServers": {
    "drawmath": {
      "command": "npx",
      "args": ["-y", "@reneturcios/drawmath", "mcp"]
    }
  }
}
```

## Docker

```bash
docker run -i ghcr.io/cloudcorprecords/drawmath
docker run --rm ghcr.io/cloudcorprecords/drawmath convert_text '{"text":"M8"}'
```

## Development

```bash
npm install
npm run build   # tsc -> dist/
npm test        # tsx --test test/*.test.ts (fixture arithmetic only, no network)
npm run dev     # run the CLI from source
```

## License

MIT — Copyright (c) 2026 Rene Turcios