Manufacturing Case StudiesFrom Imperial Drawings to Metric Production

Background

A 50-person CNC shop purchased new German metric-only machines while most drawings and shop habits were still in inches. They needed a safe, low-friction way to transition operators and processes to metric without scrap.

The Challenge

• Three new German CNC machines supported metric units only (G21 by default).
• 80% of legacy part drawings were still dimensioned in inches and imperial tolerances.
• Operators were unfamiliar with metric tolerances and surface finish specifications.
• Management expected a learning curve with scrap and rework during the transition.

Results

• Zero scrap parts in the first month of running metric-only jobs.
• Setup time reduced by approximately 30% by pre-calculating allowances and metric dimensions.
• Over 200 drawings converted from imperial to metric within two weeks.
• Successfully delivered a multi-million dollar order to a European customer on schedule.

Tools Used

Background

An automotive supplier needed to send a clean, metric-ready RFQ package to Chinese manufacturers while their internal BOM was fully in imperial units.

The Challenge

• RFQ BOM contained more than 300 line items with imperial dimensions only.
• Chinese suppliers requested metric drawings, material grades, and tolerances.
• Manual conversion in spreadsheets risked transcription errors and inconsistent rounding.
• Engineering and purchasing teams had limited time before the RFQ deadline.

Results

• Completed a dual-unit BOM (inch and mm) for all 300+ lines in one working day.
• Reduced potential manual conversion errors by centralizing calculations in one tool.
• Improved supplier response quality with consistent metric tolerances and material notes.
• Shortened RFQ preparation time by more than 60% compared to previous projects.

Tools Used

Background

A maintenance team needed metric equivalents for discontinued imperial fasteners while maintaining safety and certification requirements.

The Challenge

• Legacy aircraft documentation specified imperial fasteners that were difficult to source.
• Switching to metric required verifying thread fit, strength grade, and wrench sizes.
• Any substitution had to respect aerospace safety and regulatory requirements.
• Procurement needed clear guidance for when a metric alternative was acceptable.

Results

• Identified metric substitutes for critical imperial fasteners with clear compatibility notes.
• Standardized procurement notes and wrench size references for technicians in the field.
• Reduced sourcing lead time by opening up local metric fastener suppliers.
• Avoided last-minute AOG (aircraft on ground) situations due to missing hardware.

Tools Used

Background

A medical device manufacturer needed to modernize decades-old imperial drawings while keeping regulatory documentation intact and traceable.

The Challenge

• Legacy drawings from 40–50 years ago used imperial dimensions, tolerances, and material notes.
• Regulatory files and quality procedures required any new metric drawing to be traceable to the original.
• Engineering teams needed a consistent way to convert tolerances and surface finishes to metric.
• BOMs, inspection sheets, and supplier documentation all had to be updated together.

Results

• Created dual-unit drawings and BOMs that preserved the original imperial intent.
• Mapped ANSI tolerances to ISO fits for critical features and assemblies.
• Improved clarity for international suppliers without rewriting the entire documentation set.
• Established a repeatable playbook for future legacy-to-metric conversion projects.

Tools Used

Background

A US-based 3D printing service needed consistent metric-ready models and documentation for European clients while its design intake was mostly in imperial units.

The Challenge

• STL and CAD models arrived with mixed or ambiguous units (inch vs mm).
• Threaded features and clearance holes had to be re-checked when switching to metric hardware.
• Service-level agreements required predictable dimensional accuracy across units and materials.
• Internal teams needed simple tools to verify and document unit assumptions for each project.

Results

• Standardized intake checks for model units and critical dimensions before quoting.
• Created internal reference charts for common imperial-to-metric hole and thread conversions.
• Reduced reprints caused by unit misunderstandings and mismatched hardware.
• Improved customer confidence with clearly documented unit assumptions in quotations.

Tools Used

Background

A mold and die shop needed a fast and reliable way to estimate material, machining allowances, and costs when quoting metric-only international projects based on imperial experience.

The Challenge

• RFQs from overseas OEMs specified metric-only dimensions and tolerances.
• Internal cost models and tooling standards were developed around imperial sizes.
• Engineers needed to quickly approximate blank sizes, machining allowances, and stock usage.
• Sales teams required defensible, documented estimates to win bids without underpricing.

Results

• Prepared competitive quotes faster by standardizing how imperial experience mapped to metric projects.
• Used consistent machining allowances to avoid underestimating material and machining time.
• Reduced back-and-forth with prospects by providing clear, unit-consistent breakdowns.
• Won complex international projects while maintaining gross margin targets.

Tools Used