A free, 16-page engineering handbook on Geometric Dimensioning and Tolerancing (GD&T) based on ASME Y14.5-2018 (R2024). It explains every geometric characteristic with 3D models, the datum reference frame, modifiers, MMC bonus tolerance and a complete worked example with an inspection calculation.
Written for design, manufacturing and QA / QC engineers, inspectors and students. Free download, no sign-up.
What is inside
- Introduction: what GD&T is and what changed in ASME Y14.5-2018 (concentricity and symmetry removed, the dynamic profile modifier, new datum terms).
- Fundamentals: feature of size, MMC / LMC, MMB / LMB / RMB, virtual condition, Rule #1 and the anatomy of a feature control frame.
- Symbols and modifiers: all 12 geometric characteristics plus modifiers and dimension symbols.
- Datums: the 3-2-1 datum reference frame, datum targets and datum features of size.
- The controls: form, orientation, position, profile and runout, each on a 3D model with how to read, apply and check it.
- Worked example: a complete bracket drawing with a position inspection calculation (pass / fail with MMC bonus).
- Selection guide: which control to use for which functional requirement, common mistakes and references.
The 12 geometric characteristics in ASME Y14.5-2018
| Characteristic | Category | Datum needed? |
|---|---|---|
| Straightness | Form | No |
| Flatness | Form | No |
| Circularity | Form | No |
| Cylindricity | Form | No |
| Perpendicularity | Orientation | Yes |
| Parallelism | Orientation | Yes |
| Angularity | Orientation | Yes |
| Position | Location | Usually |
| Profile of a line | Profile | Optional |
| Profile of a surface | Profile | Optional |
| Circular runout | Runout | Yes (axis) |
| Total runout | Runout | Yes (axis) |
Concentricity and symmetry were removed in the 2018 edition. Use position, profile or runout instead.
Example page: worked example and inspection calculation
Built for oil and gas equipment
Each control is linked to real valve, wellhead and pump features: flatness on flange and gasket faces, perpendicularity of a stem bore to the bonnet face, position of bolt-hole patterns on API 6B flanges and runout on pump shafts and valve stems.
Need GD&T applied to your drawings?
Rapid Global provides wellhead, subsea and valve engineering to API standards, including legacy drawing conversion with GD&T applied per ASME Y14.5-2018. Send us the part and its function at sales@rapidglobaleng.com.
This handbook is an educational summary and is not a substitute for ASME Y14.5. ASME and Y14.5 are marks of the American Society of Mechanical Engineers; Rapid Global is not affiliated with or endorsed by ASME.