GD&T Services

GD&T and tolerance analysis per ASME Y14.5

Proper tolerance schemes that reflect functional requirements. Traceable stack-ups that show where variation comes from. Manufacturing-ready callouts that inspectors can measure.

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Problems we solve

GD&T issues often surface late, during manufacturing or assembly, when fixes are expensive. We help teams get tolerances right earlier in the design process.

Drawings have inconsistent or ambiguous tolerance callouts
Stack-ups aren't documented, making root cause analysis difficult
Datum reference frames are undefined or don't reflect assembly function
Manufacturing rejects parts that technically meet print requirements
Tolerance schemes copied from old drawings without re-evaluation
Inspection reports and drawings disagree on measurement methods
Design changes invalidate existing tolerances without review

What you receive

Documented outputs your team can use directly. No black-box analysis.

Tolerance stack-up spreadsheets

Traceable analysis showing each contributor, sensitivity, and resulting assembly variation. RSS and worst-case methods.

Drawing markup and review

Redlined drawings with corrected or improved GD&T callouts, ready for drafting update.

Datum reference frame documentation

Clear documentation of DRF selection rationale tied to functional requirements and assembly constraints.

Tolerance allocation recommendations

Suggested tolerance values based on process capability data and cost-quality tradeoffs.

GD&T training materials

Custom reference guides for your team explaining project-specific tolerance decisions.

Our approach

A systematic process that connects functional requirements to manufacturable tolerances.

1

Review requirements

Understand functional requirements, assembly sequence, and manufacturing constraints that drive tolerance decisions.

2

Establish datum reference frame

Define DRF based on how parts locate and constrain in the assembly. Document rationale for each datum selection.

3

Define tolerance scheme

Select appropriate geometric controls (position, profile, runout, etc.) and assign values based on function and process capability.

4

Validate with stack-up

Build tolerance stack-up to verify assembly requirements are met. Iterate on allocations as needed.

Standards we work with

We apply current standards correctly and can help update legacy drawings to modern practice.

ASME Y14.5-2018

Dimensioning and Tolerancing standard for mechanical drawings

ASME Y14.5-2009

Prior revision, still common in legacy drawings

ISO GPS

ISO Geometrical Product Specifications for international projects

ASME Y14.43

Dimensioning and Tolerancing Principles for Gages and Fixtures

What we check

  • Feature control frame syntax and completeness
  • Datum feature identification and precedence
  • Material condition modifier usage
  • Tolerance zone interpretation clarity
  • Inspection method feasibility
Product

We built DatumPilot to help engineers interpret GD&T faster

DatumPilot parses feature control frames and explains tolerance zones in plain language. Upload a drawing or type a callout, and get an instant breakdown of what it means and how to measure it.

Try DatumPilot free ↗

Representative engagements

Examples of GD&T work we've delivered. Details anonymized to protect client confidentiality.

Automotive Supplier

Challenge

Sealing interface tolerance stack-up for a powertrain housing showed marginal results. Customer required demonstration of 6-sigma capability.

Outcome

Rebuilt stack-up with measured process data, identified two contributors consuming 80% of tolerance budget, recommended targeted tolerance tightening. Passed customer PPAP review.

Industrial Equipment

Challenge

Legacy drawings used outdated 1994 GD&T symbology. New manufacturing partner couldn't interpret callouts consistently.

Outcome

Updated 47 drawings to ASME Y14.5-2018, established datum reference frames based on assembly function, created interpretation guide for shop floor.

Common questions

Do you work with ISO GPS or just ASME standards?

We work with both. Many projects require ASME Y14.5 for North American manufacturing and ISO GPS for European suppliers. We'll recommend the appropriate standard based on your supply chain and customer requirements.

Can you review existing drawings without access to CAD files?

Yes. Drawing review and markup can be done from PDF or print. For stack-up analysis, we'll need nominal dimensions and may request CAD for complex geometry.

How do you handle tolerance stack-ups for assemblies with many parts?

We build modular stack-ups that can be linked. Each stack-up traces from a functional requirement back through the tolerance chain. Sensitivity analysis shows which contributors matter most.

What information do you need to start a tolerance analysis?

At minimum: the assembly drawing or model, the functional requirement (gap, clearance, alignment), and the parts involved. Process capability data helps us make realistic recommendations.

Do you provide training for our engineering team?

Yes. We can deliver GD&T training sessions ranging from fundamentals to advanced topics. Training can be tailored to your specific products and common tolerance challenges.

Need GD&T expertise on your project?

Tell us about your tolerance challenges. We'll review the situation and outline how we can help.

Request engineering support