Return to Services Page
Return to PS Home Page Go To About PS Page Go To Services Page Go To Useful Tidbits Page How To Contact Profile Services

Available Services

ASME Y14.5M-1994
Geometric Dimensioning & Tolerancing

GD&T Is ... Geometric Dimensioning & Tolerancing (GD&T) is an engineering communication tool. It is a concise, mathematical language with defined symbols, syntax and application rules. GD&T is a proven way to consistently communicate an engineer's intentions to manufacturing and inspection teams.

Why GD&T ...

Start with what you know about your current (non-GD&T) engineering and manufacturing practices;

  • Parts don't always fit even though they fall within dimensional specs
  • Parts are being individually "fitted" or reworked to mate other parts
  • Parts are being scrapped because they are not what the designer had envisioned
  • Parts pass by one inspector, but fail by others
  • Engineering drawings are marked-up and revised frequently
  • Engineering resources have to verbally explain to the machinists what they want
  • Frequent "Use As Is", "Subject To Test", and "Replace on Failure" dispositions for non-conformances
  • Tweaking tolerances repeatedly, but never hitting the "perfect" combination
  • ... you get the idea ...

Now look at your costs;

  • Rework increases component costs and ties up equipment that could be making more parts ... lost opportunity
  • Scrap is an absolute waste, typically unrecoverable
  • Inspection of completed parts means that any defects detected don't help improve your process and prevent future occurances
  • Costs due to errors and omissions in engineering snowball the longer they take to detect

The problems associated with traditional linearly-toleranced systems;

  • Form (straightness, flatness, circulararity, cylindricity) of the design feature isn't considered, and has no way to control non-linear surfaces
  • Features are commonly located (dimensioned) from an external edge of the part which is non-functional
  • Assumptions and interpretations must be made by the machinist as to what a designer means
  • Tolerances are cumulative, not independent
  • Tolerance stack-up calculations don't account for form variance, a significant source of error
  • The engineering drawing does not indicate how the inspector will set up the part to verify the features

What Can GD&T Do For You ...

Geometric Dimensioning & Tolerancing isn't the solution to all your problems, but it can help you control costs associated with engineering and manufacturing mistakes, and provides a good starting point for many other quality and productivity intitiatives; Lean, Six-Sigma, standardization, and others.

GD&T effectively communicates the size and form of features on the workpiece, and locates them relative to functional datums.

  • Functional datums establish how the part will be set up for inspection, so that the results are repeatable and consistent
  • Application of in-process metrology (inspection) of indicator factors will allow you unprecedented control over your process so that final-article inspection becomes unnecessary except on a spot-check basis
  • Use of GD&T Tolerance-Stack-Up Techniques means that you can trade-off tolerances of size and position, giving "bonus tolerances"

GD&T won't give you instant results. It takes time for all your resources to learn the language. Designers need to understand and correctly apply the controls and rethink the functional requirements. In-house and external manufacturing must understand how to achieve the controls using their fabrication techniques. Quality teams must be able to set up the part correctly, read and verify the controls. Once you get the fundamentals in place, you can determine your actual manufacturing capabilities, start to identify waste and errors, and take corrective measures. It takes time and commitment, but it works.

What can Profile Services do for you ...

Jim Sykes, P.Eng, GDTP-S is ASME certified as a GD&T Professional at the Senior Level in the Y14.5M-1994 standard.

Profile Services can develop an implementation plan, provide or coordinate training, work with internal and external resources, and mentor your team throughout the implementation. Profile Services can audit your current engineering and GD&T practices for proper application, and we can provide Tolerance Analysis services. We will help you to succeed in your current market and expand into new areas.