SME
Engineering Graphics & CAD
Dimensioning and GD&T basics
Use this for “A feature control frame shows a small parallelogram, the flatness symbol. Which category is that, and does it need a datum?”
Sort
Which category does the symbol control?
Tap a card, then tap its group.
Ask what the tolerance zone is held to: the feature’s own shape, an angle, a place, a true outline or a turning axis.
Assumptions
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Form controls need no datum; the other four are measured from datums.
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Concentricity and symmetry were withdrawn from ASME Y14.5 in 2018; older drawings still carry them.
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.
More problem types
Bonus tolerance at MMC
Use this for “A hole sized Ø10 to Ø10.2 mm has position Ø0.1 at MMC and measures Ø10.15. How much position tolerance does it get?”
Virtual condition: do the parts fit?
Use this for “A hole is Ø10 at MMC with position Ø0.1; the pin is Ø9.8 at MMC with position Ø0.05. Will they always assemble?”