Runout and Concentricity Flashcards

What is the key difference between circular runout and total runout?

Answer: Circular runout applies to a single cross-section while total runout applies along the entire surface

Circular runout measures deviation at individual cross-sections, whereas total runout accumulates error across the entire length of the surface.

When a runout tolerance is applied to a conical surface, what does the tolerance zone represent?

Answer: Two lines along the cone surface separated by the tolerance value

For conical surfaces, the runout tolerance zone consists of two lines on the cone surface separated by the tolerance value, measured perpendicular to the surface.

A shaft has a total runout tolerance of 0.05 mm. During inspection, the FIM (Full Indicator Movement) reading is 0.04 mm. The part is:

Answer: Accepted because the FIM is within the 0.05 mm tolerance

The part passes because the measured FIM of 0.04 mm is less than the specified total runout tolerance of 0.05 mm.

Concentricity is most accurately described as a control of:

Answer: The median points of diametrically opposed surface elements relative to a datum axis

Concentricity controls the location of the derived median points of all diametrically opposed surface elements, not the surface itself.

Which of the following characteristics makes concentricity difficult to verify?

Answer: It requires deriving median points from opposing surface elements rather than direct surface measurement

Finding median points of diametrically opposed elements requires complex calculations, making concentricity verification more difficult than runout.

A designer wants to control wobble of a rotating disk face. Which GD&T control is most appropriate?

Answer: Circular runout applied to the face

Circular runout applied to a face (axial runout) directly controls wobble of a rotating surface relative to a datum axis.

In GD&T, what does MMC (Maximum Material Condition) bonus tolerance apply to for runout callouts?

Answer: MMC bonus tolerance is not applicable to runout tolerances

Runout is a surface control and cannot use MMC or LMC modifiers because it applies directly to surfaces, not to axes or center planes.

Which datum reference is required for a runout tolerance callout?

Answer: A datum axis

Runout tolerances always require a datum axis because the surface elements are measured relative to rotation about that axis.

A cylindrical surface has a circular runout tolerance of 0.03 mm and is also controlled by a size tolerance of ±0.1 mm. Which statement is correct?

Answer: Both tolerances must independently be satisfied

Size and runout are independent controls; a feature must conform to both its size tolerance and its runout tolerance separately.

Total runout when applied to a cylindrical surface simultaneously controls which combination of errors?

Answer: Cylindricity, coaxiality, and taper

Total runout on a cylinder controls all surface variations including out-of-roundness, wobble, taper, waviness, and coaxiality errors.

A part drawing shows a runout callout with two datum references (e.g., A-B). What does this typically indicate?

Answer: The datum axis is established by two datum features used together

Two datum references for runout typically establish a common datum axis from two separate datum features used simultaneously.

Why is symmetry sometimes used as an alternative to concentricity for symmetric features?

Answer: Symmetry is easier to apply to non-round features than concentricity

Symmetry controls the median points of features relative to a datum plane, making it applicable to non-cylindrical symmetric features where concentricity is not appropriate.

When inspecting total runout on a stepped shaft, how many dial indicator passes are required?

Answer: One pass across the entire controlled surface

Total runout requires the indicator to traverse the entire controlled surface in a single continuous sweep while the part rotates.

A runout tolerance frame contains the symbol for circular runout and the value 0.02. Where is the leader arrow typically directed?

Answer: To the surface being controlled

The feature control frame leader arrow points to the surface being controlled by the runout tolerance, not the datum.

What instrument is most commonly used to measure runout in a production environment?

Answer: Dial test indicator (DTI) with the part rotating on centers or in a chuck

A dial test indicator placed against the surface while the part rotates on centers or in a V-block is the standard production method for measuring runout.

If a shaft is bent (curved axis), which runout measurement will show the largest FIM reading?

Answer: Total runout along the full length

Total runout captures all cumulative surface deviations including the effect of a bent axis along the entire length, giving the largest FIM reading.

Concentricity is removed from ASME Y14.5-2018. What control replaces it for most design intents?

Answer: Coaxiality using position

ASME Y14.5-2018 removed concentricity and recommends using position applied to the axis (coaxiality) as a more verifiable replacement.

A print specifies circular runout of 0.05 mm on a journal bearing surface. The measured FIM at one cross-section is 0.06 mm. What action should be taken?

Answer: Reject the part as it exceeds the specified tolerance

Circular runout must be within tolerance at every cross-section; a single cross-section exceeding 0.05 mm causes rejection.

Which of the following best describes the tolerance zone for total runout on a cylindrical surface?

Answer: Two coaxial cylinders with a radial distance equal to the tolerance value

The total runout tolerance zone for a cylinder is defined by two coaxial cylinders, one inside the other, separated by the stated tolerance value.

On a drawing, runout is specified with datum reference A, which is a short cylindrical feature. What concern might an inspector raise?

Answer: Short datum features can be less stable for establishing an accurate axis

Short datum features provide limited constraint for establishing a stable axis, which can introduce uncertainty in the runout measurement.