ASME GDTP Senior Level flashcards
ASME GDTP Senior Level · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Rule #1 Envelope Principle
- Where only a size dimension is specified for a regular feature of size, the limits of size define a perfect-form envelope at MMC that the actual feature may not violate.
- Basic Dimension
- A theoretically exact dimension enclosed in a rectangle, used to establish the true profile or true position of features; it carries no tolerance itself.
- Feature Control Frame Order
- Reads left to right: geometric characteristic symbol, tolerance zone value, material condition modifier (if any), then datum references in order of precedence.
- Material Condition Modifiers
- MMC (M in a circle) allows bonus tolerance as the feature departs from maximum material; LMC (L) uses least material; RFS (no modifier) is the default fixed tolerance.
- Regular Feature of Size
- A cylindrical or spherical surface, or a set of two opposed parallel surfaces, each associated with a single size dimension and no datums.
- Datum Feature vs Datum
- The datum feature is the actual part surface or feature of size; the datum is the theoretically exact plane, axis, or point derived from it by the simulator.
- Datum Reference Frame
- Three mutually perpendicular planes (or axes/points) established by primary, secondary, and tertiary datum features in the order listed in the feature control frame.
- Datum Precedence Constraint
- The primary datum feature constrains three degrees of freedom, the secondary two, and the tertiary one, in the order listed; the order is not interchangeable.
- Datum Shift
- When a datum feature of size is referenced at MMB, the datum simulator is a fixed boundary at virtual condition, allowing the part to shift within that boundary.
- Flatness Control
- The surface must lie between two parallel planes separated by the tolerance value; no datum is referenced and the zone is not related to any datum.
- Circularity (Roundness)
- Each cross-section perpendicular to the axis must lie between two concentric circles whose radial separation equals the tolerance; evaluated per cross-section.
- Cylindricity Control
- The entire cylindrical surface must lie between two coaxial cylinders whose radial separation equals the tolerance; controls roundness, straightness, and taper simultaneously.
- Form Tolerance Datum Rule
- Form controls (straightness, flatness, circularity, cylindricity) are independent of datums; no datum references are permitted in the feature control frame.
- Perpendicularity Control
- The toleranced surface or axis must lie within a zone perpendicular to the datum plane or axis within the stated tolerance; requires at least one datum.
- Angularity Control
- The toleranced feature must lie within a zone oriented at the basic angle relative to the datum; the basic angle is shown without a tolerance.
- Parallelism Control
- The toleranced feature must lie within a zone parallel to the datum; the tolerance zone is oriented, not located, relative to the datum.
- Orientation vs Location
- Orientation controls (perpendicularity, angularity, parallelism) control the angle to a datum but do not locate the feature; location controls position it.
- Position Tolerance Zone
- A cylindrical zone (for holes/shafts) or two parallel planes (for slots) centered on the true position established by basic dimensions and datums.
- Concentricity Control
- Controls the median points of opposed elements of a feature of size relative to a datum axis; difficult to verify and rarely used in modern practice.
- Composite Position Tolerance
- Two single-segment frames: the pattern-locating frame (PLTZF) controls pattern location to datums; the feature-relating frame (FRTZF) controls feature-to-feature location.
- Profile of a Surface
- Controls location, orientation, and form of a surface relative to a true profile defined by basic dimensions; the tolerance zone is bilateral by default.
- Profile of a Line
- Controls the profile of a cross-section (line element) relative to the true profile; it is a 2D control and does not control the surface between cross-sections.
- Unilateral Profile Tolerance
- A profile tolerance shown with a phantom line and a tolerance value on one side of the true profile; the zone lies entirely on that side.
- Profile Without Datums
- When no datums are referenced, a profile tolerance controls only form and orientation of the surface, not its location relative to other features.
- Circular Runout
- Controls the variation of a surface element during one revolution about a datum axis; the indicator reading (FIM) must not exceed the tolerance.
- Total Runout
- Controls the entire surface (all elements) during rotation about a datum axis; the indicator reading must not exceed the tolerance over the full surface.
- Runout Material Condition
- Runout tolerances are always RFS; material condition modifiers (MMC, LMC) do not apply to circular or total runout controls.
- Virtual Condition
- The boundary equal to MMC size minus (internal) or plus (external) the geometric tolerance; the feature may not violate this boundary.
- Bonus Tolerance
- The amount the actual mating size departs from MMC (internal) or toward MMC (external), added to the stated geometric tolerance when MMC is specified.
- Zero Tolerance at MMC
- A zero geometric tolerance at MMC requires perfect form at MMC and provides bonus tolerance as the feature departs from MMC toward LMC.
- Functional Gaging
- Verifies MMC requirements by simulating the virtual condition boundary; a functional gage checks conformance to the worst-case boundary, not the actual size.
- CMM Inspection
- Measures actual feature geometry and computes deviation from true position or profile; can verify RFS and MMC requirements with software and bonus calculation.