Drawing Converter MCP Server

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.

"Convert bracket.pdf to imperial and tell me what replaces the M8 thread"
        │
        ▼  (your AI assistant calls the tools)
extract_drawing_text ──► classify values ──► convert_drawing_pdf
                                                   │
                                                   ▼
                                    bracket.imperial.pdf  ✓ Ø30 H7 → Ø1.1811 H7
                                                          ✓ M8     → 5/16-18 UNC

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 mcp add drawing-converter -- npx -y drawing-converter-mcp

Claude Desktop

Add to claude_desktop_config.json (Settings → Developer → Edit Config):

{
  "mcpServers": {
    "drawing-converter": {
      "command": "npx",
      "args": ["-y", "drawing-converter-mcp"]
    }
  }
}

Cursor

Add to Cursor — or add to ~/.cursor/mcp.json:

{
  "mcpServers": {
    "drawing-converter": {
      "command": "npx",
      "args": ["-y", "drawing-converter-mcp"]
    }
  }
}

VS Code (GitHub Copilot)

code --add-mcp '{"name":"drawing-converter","command":"npx","args":["-y","drawing-converter-mcp"]}'

Windsurf / other stdio clients

Any client that launches stdio servers works with:

npx -y drawing-converter-mcp

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.
• Converted values are stamped over the original callouts. Always verify safety-critical dimensions before manufacturing use.

Development

This package is built from the Drawing Converter monorepo at Imnoo, where it imports the web app's conversion engine directly — so the web app and this server convert identically by construction. Every release is gated on 31 end-to-end checks that drive all five tools over stdio against a generated sample drawing.

Issues and feature requests are welcome in this repository.

About Imnoo

Imnoo is the AI-powered planning, scheduling and quoting platform for CNC manufacturers — trusted by over 3,000 shops.

One system for the whole job, not just the spindle time:

• Planning — automatic manufacturing plans, machine recommendation, raw material, catalog and purchase-part sourcing, subcontracting. Beyond milling and turning: deep hole drilling, sheet metal, casting, profile parts.
• Quoting — AI cost and cycle-time estimation for milling, turning and EDM from a 2D PDF alone; feature-by-feature costing; market-price benchmarking; hourly-rate calculation; a 24/7 instant-quoting webshop.
• Drawing intelligence — automatic tolerance extraction, 2D-to-3D matching, axis and orientation detection, generated quality-check protocols.
• CAM — AI tool recommendation, automatic toolpath and G-code generation, and connected machines feeding real production data back into every quote.
• Libraries and insights — your own tool and material libraries, plus a searchable database of every part you've ever quoted.
• IP protection — physically separated tenants, automatic drawing masking, Swiss hosting, end-to-end encryption.

Quote the complete job — not just the spindle time. Book a demo at imnoo.com

License

MIT © Imnoo AG