imnoo-team/drawing-converter-mcp

**Convert technical drawings (PDF) and engineering callouts between metric and imperial — from any MCP-enabled AI assistant.**
This Model Context Protocol server exposes the conversion engine behind metric-to-imperial-converter.imnoo.com (by Imnoo): shop-floor-precision unit conversion for dimensions, ± tolerances, ISO fit classes, threads, surface roughness and weights — including producing a converted copy of a drawing PDF with every value stamped in place.
Tools
| Tool | What it does |
| --- | --- |
| convert_value | One value, engineering-grade rounding: length (mm⇄in), tolerance deviation, GD&T value, surface roughness (Ra µm⇄µin), weight (kg⇄lb), thread designation. Returns exact + display values, derivation method and confidence. |
| convert_text | A printed callout string, notation preserved: Ø30 H7 → Ø1.1811 H7, 84±0.1 → 3.3071±0.0039, M8 → 5/16-18 UNC, 1/4-20 UNC → M6. Angles stay untouched. |
| lookup_thread | ISO metric ⇄ Unified (UNC) cross-reference: major diameters, pitch/TPI, nearest-standard matching. Omit the designation for the full M2–M30 chart. |
| extract_drawing_text | Reads a drawing PDF's text layer: indexed tokens with positions/rotation, page geometry, and a heuristic guess of the drawing's unit system. |
| convert_drawing_pdf | Writes a converted copy of the PDF with every recognised value stamped over the original callout (size and rotation matched). The source file is never modified. |
Plus a convert-drawing prompt that walks the assistant through extract → classify → convert.
**The AI-analysis step stays with your assistant.** extract_drawing_text hands the model every printed token with its position; the model decides which tokens are real values (and whether a bare 3.2 is a length or an Ra roughness) and passes that as classifications to convert_drawing_pdf. No API keys, no cloud calls — the server itself is fully deterministic and offline.
Installation
Requires Node.js ≥ 18.
Claude Code
Claude Desktop
Add to claude_desktop_config.json (Settings → Developer → Edit Config):
Cursor
**Add to Cursor** — or add to ~/.cursor/mcp.json:
VS Code (GitHub Copilot)
Windsurf / other stdio clients
Any client that launches stdio servers works with:
Example session
> **You:** Convert C:\drawings\flange.pdf to imperial.
>
> **Assistant:** *calls extract_drawing_text* — 63 tokens, source system: metric (high confidence — "mm", ISO 2768). *classifies tokens, skips the title block, marks 1.6 next to the surface symbol as roughness, calls convert_drawing_pdf* — wrote C:\drawings\flange.imperial.pdf, 17 values converted: Ø40 H7 → Ø1.5748 H7, 2× M6 → 1/4-20 UNC (nearest standard — not interchangeable), Ra 1.6 → Ra 63 µin…
Quick one-liners work too: *"what's 84±0.1 mm in inches?"* → convert_text → 3.3071±0.0039.
Precision rules
Conversions follow the same rules as the web app:
- Exact factors by international definition (25.4 mm/in, 0.45359237 kg/lb — NIST/ISO 80000).
- Display rounding mirrors shop-floor convention: a 0.01 mm step maps to 4-decimal inches; tolerance deviations keep an extra significant digit.
- Threads are resolved against an ISO-metric ⇄ UNC chart (M2–M30), tagged table for charted rows or nearest when snapped by major diameter. **Metric and inch threads are never interchangeable** — the tools say so on every thread conversion.
- Every converted value reports how it was derived (exact / rounded / table / nearest) and a confidence score.
Limitations
- **The PDF must have a text layer.** Scanned or flattened CAD exports have none — the web app handles those with in-browser OCR + AI analysis.
- One page is converted per call (page parameter, default 1); other pages pass through unchanged.
- Fractional-inch callouts (1 3/4) aren't converted yet — decimal-inch drawings work fine.