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Surface Finish & Assembly Requirements 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 Surface Finish & Assembly Requirements flashcards as text

  1. A shaft and hole assembly uses an interference fit. Which surface finish condition on the shaft would MOST likely cause the interference to be less than intended?

    Answer: Surface peaks (asperities) that are flattened during pressing

    When pressing an interference fit, surface peaks are crushed and flattened, effectively reducing the interference and the resulting holding force.

  2. The 'lay' of a surface texture is best described as:

    Answer: The predominant direction of surface marks or tool paths

    Lay refers to the predominant direction of the surface pattern, which is determined by the manufacturing process used.

  3. A drawing callout reads 'surface finish Ra 1.6 μm max'. A measured surface has Ra 1.2 μm. This surface is:

    Answer: Within tolerance

    'Max' means the Ra value must not exceed 1.6 μm; a measured value of 1.2 μm is smoother and therefore within tolerance.

  4. Which GD&T symbol, when applied to a surface, requires every point on that surface to fall within two parallel planes separated by the tolerance value?

    Answer: Flatness

    Flatness requires all surface points to lie within two parallel planes spaced by the tolerance value, with no datum reference required.

  5. In a bolted joint assembly, if the mating surfaces have excessive waviness (long-wavelength deviations), the primary risk is:

    Answer: Uneven clamp load distribution and potential fatigue cracking

    Waviness creates gaps and high-pressure contact zones in bolted joints, causing uneven clamping forces that accelerate fatigue failure.

  6. A drawing specifies a surface profile tolerance of 0.05 mm bilateral. This means each surface point must fall within:

    Answer: 0.025 mm on each side of the true profile

    A bilateral profile tolerance of 0.05 mm is split equally, allowing 0.025 mm inward and 0.025 mm outward from the true profile.

  7. When a surface finish symbol includes a value above the check mark line and a different value below it, they represent:

    Answer: Maximum Ra and minimum Ra limits

    Per ISO 1302, values above and below the check mark line represent the upper (maximum) and lower (minimum) Ra limits for the surface.