Practice Test Geeks(GD&T) Geometric Dimensioning and Tolerancing Certification Practice Test
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Datum Reference Frames Flashcards

7 cards from real GD&T practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Datum Reference Frames flashcards as text

  1. In the 3-2-1 locating principle, which datum provides the 3-point contact?

    Answer: Primary datum

    The primary datum provides 3-point minimum contact, constraining 3 degrees of freedom (1 translation + 2 rotations).

  2. A shaft diameter is called out as a secondary datum at MMC (⊕). As the shaft is produced 0.010 smaller than MMC, the datum shift available is:

    Answer: 0.010

    Datum shift equals the difference between the actual mating size and MMC; if the shaft is 0.010 under MMC, shift = 0.010.

  3. What is the purpose of using multiple datum targets (e.g., A1, A2, A3) to establish a single datum plane?

    Answer: To simulate a datum plane on a non-flat or flexible surface using discrete contact points

    Multiple datum targets simulate a plane on irregular surfaces (like castings) by defining exact contact points rather than relying on full surface contact.

  4. Which ASME Y14.5 standard section governs datum reference frames and datum feature selection?

    Answer: Section 4 — Datum Reference Frames

    ASME Y14.5 Section 4 specifically covers datum reference frames, datum features, datum feature simulators, and related concepts.

  5. A feature control frame reads: ⊕ | Ø0.010 | A | B(M) | C. What does the (M) modifier after B indicate?

    Answer: Datum B is a maximum material condition datum feature reference

    The MMC modifier (M) after a datum letter means datum shift is permitted as datum B departs from its maximum material condition.

  6. When is it appropriate to use a partial datum surface (datum target area) instead of an entire surface as a datum feature?

    Answer: When the surface is large, warped, or only a specific area is functional

    Datum target areas restrict contact to a functional zone when the full surface is too large, irregular, or when only a specific region controls part function.

  7. In a customized datum reference frame (CDRF) per ASME Y14.5-2018, what is the key difference from a standard DRF?

    Answer: CDRF can selectively constrain specific degrees of freedom using DOF indicators

    A CDRF allows designers to explicitly specify which degrees of freedom each datum constrains using u, v, w, x, y, z notation in the feature control frame.