Metric to Imperial Drawing Converter

Convert technical-drawing PDFs between metric and imperial — dimensions, tolerances, ISO fits, M⇄UNC threads and surface roughness — with every value stamped in place on the PDF.

GitHub

Documentation

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 — The System for Manufacturers | AI Planning, Scheduling & Quoting · Complete Assemblies · DFM · Tool & Material Libraries · Quoted-Parts Database · Toolpath & G-Code · Machine Connection · Webshop · ERP · Shop Analytics & Optimization · Drawing Masking & IP Security

Plan It. Schedule It. Quote It. Win It. — trusted by over 3,000 manufacturers.

Imnoo is the AI-powered planning, scheduling, and quoting platform for CNC manufacturers — your automatic production platform. One system that covers it all: automatic manufacturing planning with raw-material, catalog and purchase-part, and subcontracting sourcing; scheduling with smart reminders and AI-driven customer workflows; and AI cost and cycle-time estimation for milling, turning, and EDM — even from a 2D PDF alone. Quote complete assemblies: drop in one file and Imnoo explodes it into single parts automatically — with DFM checks, quality protocols, tolerance extraction and 2D-to-3D matching, toolpath and G-code generation, tool and machine recommendations, and connected machines feeding real production data back into every quote. Built on your own tool and material libraries and a growing database of every part you've ever quoted — powering statistics, benchmarks, and shop optimization. Extends to deep hole drilling, sheet metal, casting, and profile parts — with a 24/7 webshop, built-in ERP, hourly-rate calculation, market-price benchmarking, and imperial ⇄ metric conversion. Your data lives in its own physically separated environment — automatic drawing masking, Swiss hosting, end-to-end encryption. From messy RFQ to production-ready order, on one platform.

Planning

Automatic manufacturing planning — production plans generated straight from the quote.
Machine recommendation — every job routed to the machine that runs it best.
Catalog & purchase part management — norm parts, screws, and bought-in components recognized straight from the BOM, managed and priced alongside your machined parts.
Raw material sourcing — price, source, and order material without leaving the workflow.
Purchase part & external step sourcing — bought-in components, coating, heat treatment, and subcontracting sourced and ordered in the same flow.
Beyond milling & turning — deep hole drilling, sheet metal, casting, and profile parts.

Scheduling & Workflow

Scheduling & smart reminders — via email, Telegram, or WhatsApp. Nothing slips.
Email-to-quote automation — a messy inbox in, structured quotes out.
AI customer agents — RFQ answers, clarifications, and follow-ups handled automatically.
Built-in lightweight ERP — orders, companies, payment terms, and margins without the bulky software.

Quoting & Estimation

Complete assemblies, exploded automatically — upload one assembly file and Imnoo blows it out into single parts: every component recognized, drawings matched to the right parts, sub-assemblies nested, purchase parts pulled from the BOM. Quote the whole machine as easily as one part.
CNC quoting in one place — milling, turning, and EDM jobs quoted from a single AI-powered platform.
AI cost & cycle-time estimation — know price, time, and effort before engineering ever looks at it.
Drawing-only estimation — quote from the PDF alone. No 3D model needed.
Feature-by-feature costing — see exactly which holes, pockets, and tolerances drive the price.
Instant quotes — respond in minutes while competitors are still opening the STEP file.
24/7 instant-quoting webshop — customers upload parts and buy while you sleep.
Instant market-price benchmarking — know where your bid stands before you send it.
Hourly-rate calculation — your true machine and labor rates, always current.
Imperial ⇄ metric conversion — international RFQs without manual cleanup.

Libraries & Insights

Tool library — your cutting tools, holders, and parameters in one managed catalog.
Material library — standard and custom materials with live supplier pricing.
Quoted-parts database — every part you've ever quoted, searchable by geometry: similar part found, price found.
Statistics & analytics — win rates, margins, throughput, and quoting performance at a glance.
Shop optimization — learn from already-quoted parts to sharpen prices, spot profitable niches, and load the right machines.

Drawing Intelligence

DFM — Design for Manufacturing — manufacturability checked before you quote: undercuts, thin walls, unreachable features, and impossible tolerances flagged with the part still on the screen.
Quality check protocols — inspection plans generated automatically: stamped and numbered drawing features, inspection classes and rates, ready-to-use measurement reports.
Axis & orientation detection — AI finds the best part orientation and machining axes.
Automatic tolerance extraction — critical tolerances pulled straight off the drawing.
2D-to-3D tolerance matching — drawing requirements linked to the right model features.

CAM & Shop Intelligence

AI tool recommendation — stop searching catalogs: Imnoo suggests the exact cutting tools for every feature.
Automatic toolpath generation — from quote to machining strategy in one step.
G-code generation & estimation — generate and evaluate programs before work hits the floor.
Machine connection — your machines feed real production data back into the AI. Every quote gets smarter.

IP Protection & Data Security — Engineered Like a Swiss Vault

Physically separated data — every manufacturer runs in its own isolated environment. Your drawings, prices — never pooled with anyone else's: not for storage, not for AI training.
Automatic drawing masking & redaction — customer names, logos, and confidential data hidden before a drawing ever leaves your workflow. Share with suppliers and subcontractors without exposing whose part it is.
Your customers' IP, treated like your own — end customers' designs stay within your tenant, full stop.
Swiss hosting & end-to-end encryption — data sovereignty and security engineered to Swiss standards.
Trusted at scale — over 3,000 manufacturers run their quoting on Imnoo.

Quote the complete job — not just the spindle time.

👉 Book a demo at imnoo.com