Free ASME GDTP Senior Exam Flashcards

ASME administers separate Senior examinations for Y14.5-2009 and Y14.5-2018, and the certificate names the revision passed. Use the rules and Body of Knowledge for the edition selected in the application; passing one edition does not certify the other.

Read the geometric characteristic first, then the tolerance value and any zone or material-condition modifier, followed by datum references in their stated order of precedence. A datum modifier qualifies only the datum reference it follows.

A boxed basic dimension is theoretically exact. It defines true location, orientation, or profile; allowable variation comes from the associated geometric tolerance, not from a plus/minus tolerance on the basic dimension.

Unless an exception is specified, the feature may not violate a perfect-form envelope at MMC. As actual size departs from MMC, additional form variation is available, but every local size must remain within its size limits.

For a geometric tolerance applied to a feature of size, no modifier means RFS: the tolerance is constant regardless of feature size. For a datum feature reference, no boundary modifier means RMB, not 'datum RFS.'

A datum is a theoretically exact point, axis, line, or plane; a datum feature is the real part feature. A datum feature simulator is the theoretically exact boundary used to establish the datum. Actual inspection tooling is a physical datum feature simulator.

Three translations along mutually perpendicular axes and three rotations about those axes. A valid datum scheme constrains only the motions needed by function; it should not be assumed that every datum feature removes three freedoms.

It constrains translation normal to the plane and rotation about the two axes lying in that plane: three degrees of freedom. Translation in the plane and rotation about the plane's normal remain available.

A mutually perpendicular secondary plane normally removes one in-plane translation and rotation about the primary plane's normal: two additional degrees of freedom. It must not reconstrain motions already fixed by the primary datum.

After primary and secondary planar datums have removed five freedoms, the tertiary plane normally removes the last translation. It completes the 3-2-1 planar datum reference frame without overriding earlier precedence.

Choose the primary, secondary, and tertiary datums from the features that seat, orient, and locate the part in function or verification. Datum letters are identifiers; alphabetical order does not determine precedence.

Regardless of Material Boundary lets the datum simulator adjust to achieve contact with the datum feature while respecting higher-precedence datums. It does not create datum shift from clearance between a fixed material boundary and the actual feature.

Maximum Material Boundary fixes the datum simulator at the stated or calculated MMB. If the actual datum feature departs from that boundary, clearance may permit datum feature shift while the part remains in contact with higher-precedence simulators.

Least Material Boundary is useful when the functional requirement protects a least-material boundary, such as minimum wall thickness. The datum simulator is established at the specified or calculated LMB; any permitted datum mobility must remain consistent with that boundary.

Bonus tolerance enlarges the controlled feature's geometric tolerance because that feature departs from MMC or LMC. Datum feature shift is permitted movement of the datum reference frame from clearance at an MMB- or LMB-referenced datum feature. Calculate and justify them separately.

Two or more specified datum features act simultaneously to establish one datum from their combined simulators. They are not a primary-secondary sequence; the drawing must identify them as the multiple features used together for that single datum.

Use datum targets when contacting an entire datum feature is impractical or would not represent the functional interface. The drawing identifies the target points, lines, or areas that the simulator uses to establish the datum.

A cylindrical primary datum normally constrains two translations perpendicular to the axis and two rotations that tilt the axis. Translation along the datum axis and rotation about it remain until another datum feature constrains them.

Each feature control frame establishes the datum reference frame it explicitly cites. Do not merge omitted datums or precedence from another frame; compare the frames only when the drawing's simultaneous or relationship requirements make them interact.

It defines the specified restraint under which the part is to be evaluated. The fixture or force must reproduce that stated condition; arbitrary clamping can distort the feature and produce a result unrelated to the drawing requirement.

Two parallel planes separated by the flatness tolerance. Every point of the controlled surface must lie between them. Surface flatness references no datum because it is a form control.

Surface straightness controls each indicated line element between two parallel lines and uses no datum. Straightness of a feature-of-size axis or median line uses a geometric zone for the derived line and may be specified with a material-condition modifier.

Circularity evaluates each circular cross-section independently between two concentric circles. Cylindricity evaluates the entire cylindrical surface between two coaxial cylinders, so it also limits axial straightness and taper. Neither control references a datum.

Parallelism, perpendicularity, and angularity orient a surface, axis, or center plane to referenced datum(s). The angle is basic—implied for parallelism or perpendicularity and explicitly defined for angularity—but the zone may translate unless another control locates it.

Only when the orientation tolerance controls a feature of size through its axis or center plane. A surface orientation tolerance does not receive a material-condition modifier because the controlled surface is not itself a feature of size.

It controls the location—and, when constrained by the datum reference frame, the orientation—of a feature of size's axis, center plane, or center point relative to basic dimensions. A diameter symbol specifies a cylindrical or circular positional zone.

For perpendicular coordinate offsets ΔX and ΔY from basic location, diametrical position error is 2 × √(ΔX² + ΔY²). The factor of two converts radial center offset to the diameter of the smallest centered circular zone containing the measured center.

Allowed position tolerance = stated tolerance at MMC + departure from MMC. For a hole, departure is actual size minus hole MMC; for a shaft, it is shaft MMC minus actual size. No bonus exists if the control is RFS.

For an internal feature such as a hole, virtual condition = MMC size − geometric tolerance at MMC. This fixed worst-case inner boundary combines feature size and the specified geometric tolerance.

For an external feature such as a pin, virtual condition = MMC size + geometric tolerance at MMC. This fixed worst-case outer boundary protects assembly clearance.

The stated positional tolerance-zone size remains constant throughout the feature's size limits. Feature size still must satisfy its size tolerance, but departure from MMC or LMC does not add bonus position tolerance.

It controls the feature axis over a specified height above the part surface, where a mating fastener or pin engages. This protects assembly at the remote interface instead of checking orientation only within the thickness of the threaded or press-fit feature.

At the hole's MMC size, no positional departure is allowed. As the hole grows larger than MMC, its entire departure from MMC becomes bonus position tolerance, while the virtual-condition boundary remains equal to the hole's MMC size.

The gage pin represents the hole's virtual condition: hole MMC minus its position tolerance at MMC. This is valid only when the gage also establishes the specified datum reference frame and accounts for applicable datum boundaries.

The upper pattern-locating segment locates and orients the pattern relative to its referenced datums. The lower feature-relating segment refines feature-to-feature spacing and orientation within the pattern; only datum references actually repeated in that segment constrain it.

Each single segment creates a separately complete position requirement relative to the datums shown in that segment. A composite control links its stacked segments into one pattern-control structure, so omitted or repeated datums have different consequences.

Without a diameter symbol, position may control the slot's derived median plane between two parallel planes located by basic dimensions. If MMC or LMC is specified, the boundary and available bonus follow the width feature's material condition.

Y14.5-2009 contains concentricity and symmetry controls, while Y14.5-2018 removed them. On a 2009 drawing, they have their defined median-point meanings and should not be casually replaced by position, runout, or profile without checking design intent.

Profile of a line controls each specified two-dimensional line element. Profile of a surface controls the complete three-dimensional surface. The drawing view, leader, and scope indication determine which line elements or surfaces are included.

The theoretically exact contour comes from basic dimensions, radii, angles, and any referenced digital model. The profile tolerance creates boundaries around that true profile; it does not replace the basic definition of the contour.

Without datums, profile primarily controls form of the defined contour. With a datum reference frame, the profile zone can also control orientation and location relative to that frame, as constrained by the referenced datums.

The zone is equally disposed about the true profile. When unequal disposition is specified with the U modifier, its value states the portion of the total tolerance on the outside-of-material side of the true profile; the remainder lies on the inside-of-material side.

All-around extends the profile requirement around the continuous perimeter represented in the indicated view. All-over applies the requirement to every surface of the part unless surfaces are specifically excluded. Neither symbol should be assumed to mean only the leadered face.

Use drawing indications such as between points, boundary lines, or a defined area to state the controlled extent. The profile tolerance applies only within that specified scope; adjacent surface portions are governed by their other dimensions or controls.

The upper segment establishes the broader profile boundary relative to its datum references. The lower segment refines the profile within that boundary and uses only the datums repeated there; it cannot inherit an omitted datum by assumption.

Treat each segment as an independent, complete profile requirement with its own tolerance and datum references. Unlike a composite frame, stacked single segments do not automatically create an upper/lower pattern-refinement relationship.

Profile-zone boundaries are generated normal to the true profile at each point unless another requirement defines the evaluation. A constant offset in a drawing view is not necessarily a constant normal distance on a changing three-dimensional contour.

A broader surface-profile control can govern the three-dimensional contour, while a tighter line-profile control limits selected cross-sectional line elements. Both requirements must be satisfied over their stated scopes; the tighter line control does not erase the surface control.

Circular runout evaluates each circular line element independently during rotation about a datum axis. Total runout evaluates all line elements over the entire controlled surface during continuous rotation; on a cylindrical surface, it limits cumulative coaxiality, circularity, straightness, and taper effects.

Runout requires rotation about the referenced datum axis while measuring the controlled surface. Because runout controls a surface rather than a feature-of-size axis or center plane, MMC and LMC modifiers are not applied to the runout tolerance value.