GD&T Cheat Sheet 2026

The 30 highest-yield GD&T facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. A CMM report shows a hole axis deviated 0.18 mm in X and 0.24 mm in Y from true position. The diametral position error is: → ⌀0.60
2. In the context of GD&T datum systems, what is 'true geometric counterpart'? → The theoretically perfect form of the datum feature used to establish the datum
3. In a worst-case tolerance stack-up, how are individual tolerances combined? → They are arithmetically added, assuming all tolerances at their maximum
4. A straightness tolerance applied to the surface of a cylinder (not its axis) creates a tolerance zone that is: → Two parallel lines on the surface in the direction of measurement
5. A feature control frame reads: position | 0.3Ⓜ | A | BⓂ. What does the Ⓜ on datum B indicate? → Datum shift is allowed based on datum B's departure from MMC
6. In a datum reference frame, what is the maximum number of degrees of freedom that can be constrained? → 6
7. In GD&T, the term 'virtual condition' for an external feature at MMC is calculated as: → MMC size plus the applicable geometric tolerance
8. Which statement correctly describes 'least material condition' (LMC) for an external feature (shaft)? → The shaft is at minimum diameter
9. According to ASME Y14.5, which rule governs the relationship between size tolerance and form tolerance for an individual feature of size? → Rule #1 (Envelope Principle)
10. Under ASME Y14.5, a composite feature control frame is distinguished from a two single-segment frame by: → The composite frame uses one geometric characteristic symbol spanning both rows
11. Which of the following is the primary reason for applying a positional tolerance at Maximum Material Condition (MMC)? → To allow for the use of functional gages and provide bonus tolerance for manufacturing.
12. Which of the following is NOT a valid datum feature type in ASME Y14.5? → Theoretical perfect plane in free space
13. Which of the following orientation tolerances controls a feature at an angle of exactly 0° to a datum? → Parallelism
14. When interpreting a composite feature control frame, what is the term for the tolerance zone defined by the upper segment? → Pattern-Locating Tolerance Zone Framework (PLTZF)
15. Concentricity is most accurately described as a control of: → The median points of diametrically opposed surface elements relative to a datum axis
16. What does the 'S' modifier inside a feature control frame signify? → Spherical diameter
17. In a standard Datum Reference Frame (DRF), what is the minimum number of points of contact required for the primary datum feature to constrain the part? → Three points
18. A drawing specifies a surface profile tolerance of 0.05 mm bilateral. This means each surface point must fall within: → 0.025 mm on each side of the true profile
19. What happens to the FRTZF tolerance zone framework if no orientation datums are referenced in it? → The FRTZF zones are free to rotate and translate relative to the DRF
20. A clearance fit is achieved when the minimum clearance between mating parts is: → Positive
21. On a feature control frame, a datum letter followed by a material condition modifier (e.g., 'B(M)') means: → The datum shift allowance applies based on the actual mating size of datum feature B
22. In ASME Y14.5, which condition applies when a feature of size is at its maximum material condition (MMC) and a geometric tolerance is at its least restrictive? → Maximum Material Condition (MMC) modifier (circle M)
23. In the 3-2-1 locating principle, which datum provides the 3-point contact? → Primary datum
24. An LMC modifier is most useful for controlling which engineering concern? → Minimum wall thickness and edge distance
25. A turbine rotor requires tightly controlled vibration during operation. Which GD&T control best addresses dynamic balance concerns related to surface geometry? → Total runout on the rotating cylindrical surfaces
26. When is it appropriate to use a partial datum surface (datum target area) instead of an entire surface as a datum feature? → When the surface is large, warped, or only a specific area is functional
27. A part drawing calls out datum reference frame [A|B|C] on a position tolerance. What does the order of datums indicate? → The precedence (primary, secondary, tertiary) of datum constraint
28. The 'between' symbol in GD&T notation is used to indicate: → A tolerance applies between two specified points
29. Under ASME Y14.5, what is the default geometric tolerance condition when no modifier is shown? → Regardless of Feature Size (RFS)
30. For a part with both runout and position callouts on the same surface, which takes precedence? → Both must be independently satisfied; neither overrides the other