1.4 The Y14.5-2018 Senior Exam and What Changed from 2009
Key Takeaways
- The 2018 Senior blueprint is organized by standard section number — 10% Sections 3-6, 30% Section 7 (Datum Reference Frames), 5% Section 8, 5% Section 9, 25% Section 10 (Position), 20% Section 11 (Profile), 5% Section 12 (Runout) — with the same weights as 2009 but a 74% overall pass mark.
- Y14.5-2018 deleted concentricity and symmetry; a 2018 candidate controls those relationships with position, runout, or profile instead.
- 2018 renamed 2009's "datum feature simulator (theoretical)" back to "true geometric counterpart" and renamed "multiple datum features" to "common datum features".
- 2018 replaced the 2009 candidate-datum-set method for rocking datum features with a single default stabilized solution that minimizes separation between the feature and its true geometric counterpart.
- The dynamic profile modifier is the headline new 2018 symbol: it lets profile control form without also controlling size.
The Y14.5-2018 Senior Exam and What Changed from 2009
Quick Answer: The 2018 Senior exam uses the same seven weights as 2009 but labels them by standard section number and passes at 74% instead of 78%. The technical deltas that matter are: concentricity and symmetry deleted, dynamic profile added, "true geometric counterpart" restored, "common datum features" renamed, and a single default stabilization rule replacing the candidate datum set.
ASME runs the 2009 and 2018 Senior exams side by side. You buy one or the other, and the certificate you receive names the revision you passed. Nothing about passing 2009 grants 2018, and nothing about passing 2018 grants 2009. Section 1.2 covered how to choose; this section maps the 2018 blueprint and isolates the technical delta so that a candidate trained on 2009 material knows exactly what extra ground to cover — and so that a candidate sitting 2009 knows which 2018-only concepts to ignore.
The 2018 Senior blueprint
The 2018 outline is organized by standard section number rather than by topic name. The weights are identical to 2009:
| Section(s) | Topic | Weight | ~Questions of 150 |
|---|---|---|---|
| 3-6 | Definitions, Rules, Tolerancing, Symbology | 10% | 15 |
| 7 | Datum Reference Frames | 30% | 45 |
| 8 | Form | 5% | 8 |
| 9 | Orientation | 5% | 8 |
| 10 | Position | 25% | 37 |
| 11 | Profile | 20% | 30 |
| 12 | Runout | 5% | 8 |
Pass requires 74% overall and at least 50% in each section. The 2009 exam requires 78% overall with the same 50% floor. Both are 150 scored multiple-choice questions with a maximum duration of six hours, both are closed book, and both require knowledge of Nonmandatory Appendix B, Formulas for Positional Tolerancing.
Notice the naming shift. Where 2009 says "Location," 2018 says "Position" — because 2018 deleted the other two location controls (concentricity and symmetry) and Section 10 now contains position alone. Where 2009 says "Datum Referencing," 2018 says "Datum Reference Frames." Where 2009 says "Scope, General Dimensioning, and Symbology," 2018 says "Sections 3 through 6 (Definitions, Rules, Tolerancing, Symbology)." Same ground, different labels.
Delta 1: Concentricity and symmetry are gone
This is the largest single change. Y14.5-2009 clauses on concentricity (◎) and symmetry (⌯) controlled the median points of diametrically opposed elements or opposed surfaces. Both were RFS-only, both were extremely expensive to verify, and both were widely misapplied where position or runout was the correct control.
Y14.5-2018 deleted both symbols. On a 2018 drawing you achieve the same design intent with:
- Position on a feature of size when you care about the derived median plane or axis location — and you may use MMC, which concentricity never allowed.
- Runout when you care about the surface as it rotates about a datum axis.
- Profile when you care about the surface itself relative to a datum reference frame.
For the 2009 exam these two controls are live BoK content (see Section 10.4). For the 2018 exam, a question naming concentricity is testing whether you know it no longer exists.
Delta 2: Dynamic profile
The dynamic profile modifier is the marquee new 2018 symbol. Ordinary profile applied to a non-planar feature controls size, form, orientation, and location together, because the two boundary offsets from the true profile are fixed. The dynamic modifier makes the offset between the boundaries stay constant while the boundaries themselves float, so profile controls form without also constraining size. On a hole, dynamic profile with no datum references behaves like cylindricity; on a complex contour it does what no other single symbol could previously do. Expect at least one 2018 Profile question on it.
Delta 3: Terminology reversals
Two terms flipped between revisions, and the exam writers know it:
| 2009 term | 2018 term |
|---|---|
| Datum feature simulator (theoretical) | True geometric counterpart |
| Multiple datum features (A-B) | Common datum features |
The concepts did not change; the words did. "True geometric counterpart" had existed in 1994, disappeared as a defined term in 2009, and returned in 2018. If you learned the 2009 vocabulary, you must be able to read the 2018 vocabulary and vice versa.
Delta 4: Default stabilization replaces the candidate datum set
When a primary datum feature is convex and rocks on its simulator — or when a datum feature of size referenced RMB can settle in more than one way — 2009 permitted a candidate datum set: a family of permissible datums, and the part passed if any member of the set worked. 2018 replaces this with a single default stabilized solution: the part is adjusted to the one solution that minimizes the separation between the datum feature and its true geometric counterpart. One answer, not a search. This tightens inspection repeatability and it is a favorite 2018 Datum Reference Frames question.
Delta 5: Smaller items on the 2018 Senior body of knowledge
The published 2018 Senior body of knowledge also names a few items the 2009 list does not:
- Dimensions related to an origin (the origin symbol, which fixes which surface is the measurement origin in a plus-minus dimension).
- Average diameter listed under Form, for nonrigid parts.
- Profile of a line as a refinement of profile of a surface, called out explicitly.
- Tolerance zone shape (2018) where 2009 says "definition of the tolerance zone."
- The from-to symbol for designating the extent of a requirement between two points.
What transfers untouched
Do not over-rotate on the delta list. Degrees of freedom, datum precedence, datum targets, MMB/LMB/RMB, datum shift, Rule #1, all four form controls, all three orientation controls, position and its boundaries, bonus tolerance, projected tolerance zones, composite frames, profile scope and disposition, and both runout controls behave the same way in both revisions. The arithmetic in Chapters 8, 9, and 14 of this guide is revision-neutral. Roughly nine-tenths of your preparation serves either exam; budget a focused delta review for the last tenth.
On the Y14.5-2018 Senior blueprint, what weight is assigned to Section 7, Datum Reference Frames, and what overall score is required to pass?
A drawing prepared to Y14.5-2018 needs the median plane of a slot located relative to a datum reference frame. Which approach matches the 2018 standard?
A primary planar datum feature is slightly convex and rocks on its simulator. How does Y14.5-2018 resolve which datum is established?
What does the dynamic profile modifier introduced in Y14.5-2018 accomplish?