🚧 Under construction — VoTechWorks is being built. A free tech program — complimentary, as our commitment to get America working.
voTechWorksGrade 13 · a vocational technology learning center, by urbanicity
newSchoolWorks.com › VoTechWorks › Manufacturing & Marine › CNC Machining › Blueprint Reading and GD&T for CNC Machining › Lesson 10
MFG-CNC14-02 · Lesson 10 · 10 clock hours · demo

Profile, Runout, and Free-State Tolerances

Objective. Students interpret profile of a line, profile of a surface, circular runout, and total runout callouts and measure total runout on a turned part using a dial indicator and V-blocks.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed engineer or certified journey-level tradesperson or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Profile, Runout, and Free-State Tolerances

Profile of a Line and Profile of a Surface

Profile tolerances control the shape, size, orientation, and location of features — especially curves and contoured surfaces that cannot be fully described by simple diameter or length dimensions alone. ASME Y14.5-2018 defines two types.

Profile of a line controls cross-sectional shape at any single slice through the feature. Think of it as a 2-D check: a CMM probe or gauge traces one path across the surface. The tolerance zone is a band — centered on the true profile — within which the line must fall.

Profile of a surface extends that control across the entire surface in three dimensions. Every point on the feature must fall within the tolerance zone. Profile of a surface is the more complete and more common callout for machined contours.

Bilateral and Unilateral Tolerance Zones

The default profile zone is bilateral and equal: the band is split evenly on both sides of the true profile. A callout reading ⌖ 0.4 (with no modifier) means 0.2 mm lies outside the true profile and 0.2 mm lies inside.

When the zone is shifted entirely to one side, it is unilateral. ASME Y14.5-2018 uses a parenthetical value and a small circle with U to indicate an unequal or unilateral distribution. For example, ⌖ 0.6 (U 0.4) places 0.4 outside and 0.2 inside the true profile. Always check whether the drawing follows the 2018 standard or an older revision before interpreting the zone direction, because notation changed between editions.

When sketching the zone, draw the true profile first, then offset the boundary curves by the specified amounts on each side. Label which side is material and which is open space — this is especially important for aerospace or marine hardware where undercut or overcut each carries different structural consequences.

Runout: Two Closely Related Controls

Runout tolerances apply to surfaces of revolution — turned parts, shafts, flanges, bearing journals, and propeller hubs common in the marine sector. Both types require a datum axis, typically established by a precision spindle, centers, or — in bench inspection — V-blocks on a surface plate.

Circular runout is a 2-D control. The indicator is fixed at one axial location, the part rotates one full revolution (360°), and the Full Indicator Movement (FIM) is recorded. FIM is the total range of indicator travel: maximum reading minus minimum reading during that single rotation. Each circular cross-section is checked independently; the part passes if FIM at every checked position is within the tolerance.

Total runout is a 3-D control. The indicator traverses the entire surface axially while the part rotates, measuring cumulative error from all sources: eccentricity, taper, out-of-roundness, wobble, and surface irregularity all contribute simultaneously. The single FIM value recorded over the full sweep must fall within the total runout tolerance.

This is why a part can pass circular runout and fail total runout: if a shaft has a slight taper or a gradual conical form, each circular slice may be round and centered, producing acceptable FIM at every individual station — yet the combined axial sweep reveals that the surface drifts away from the datum axis, producing a larger accumulated FIM over the full length.

Measuring Total Runout with V-Blocks and a Dial Test Indicator

1. Set up safely. Secure V-blocks to the surface plate. Inspect the surface plate for burrs or chips before placing anything on it — a chip under a V-block introduces tilt error. Wear safety glasses. Edges of shafts can be sharp; handle with gloves when moving the part, but remove gloves before operating any rotating equipment.

2. Place the datum journals of the stepped shaft in the V-blocks. The datum journals must be clean and free of nicks.

3. Zero the dial test indicator on the surface to be measured. Use the lightest contact pressure that maintains consistent contact.

4. Rotate the shaft slowly and continuously through 360° while traversing the indicator along the measured surface. Record the FIM — maximum reading minus minimum reading.

5. Repeat at the three specified axial positions noted on the drawing or measurement log.

6. Compare each FIM to the total runout callout. Record a conformance decision: PASS if FIM ≤ tolerance, FAIL if FIM > tolerance.

Free-State Tolerances

Free-state variation applies to non-rigid parts — thin-walled rings, gaskets, flexible marine hose fittings — that distort under their own weight or when released from clamping forces. ASME Y14.5-2018 uses the free-state symbol (F in a circle) to indicate that the measurement is taken with the part unconstrained. Without this modifier, GD&T measurements are generally taken with the part restrained as it would be in assembly. Always note whether a callout carries the free-state modifier before fixturing the part for inspection.

Safety Notes

Key terms9

Profile of a LineA GD&T control that limits the shape of a feature at each individual 2-D cross-sectional slice; the tolerance zone is a band around the true profile at that slice.
Profile of a SurfaceA GD&T control that limits every point on an entire 3-D surface to fall within a band offset from the true profile; more complete than profile of a line.
Bilateral Tolerance ZoneA profile tolerance zone split on both sides of the true profile; equal bilateral means each side receives half the total tolerance value.
Unilateral Tolerance ZoneA profile tolerance zone placed entirely on one side of the true profile; indicated in ASME Y14.5-2018 with the U modifier symbol.
Circular RunoutA 2-D runout control measuring FIM at a single fixed axial location during one full rotation of the part about its datum axis.
Total RunoutA 3-D runout control measuring FIM across the entire surface — axially and rotationally — in a single continuous sweep; it captures all combined errors simultaneously.
Full Indicator Movement (FIM)The total range of dial indicator travel during a runout measurement — maximum reading minus minimum reading; the value compared directly to the runout tolerance.
Free-State SymbolAn F enclosed in a circle; indicates that a GD&T measurement is taken with the part unconstrained and unrestrained, applicable to non-rigid or flexible parts.
Datum AxisThe theoretical axis derived from a datum feature (such as a precision journal in V-blocks) from which runout and other geometric tolerances are measured.

Worked examples4

1. A total runout callout reads ⌀ 0.05 mm. A stepped shaft is placed in V-blocks. During a full axial sweep, the dial test indicator reads a maximum of +0.038 mm and a minimum of −0.019 mm. Does the part conform?
  1. Calculate FIM: FIM = maximum reading − minimum reading = 0.038 − (−0.019) = 0.038 + 0.019 = 0.057 mm.
  2. Compare FIM to the callout: 0.057 mm > 0.050 mm.
  3. Record the conformance decision: FAIL — total runout exceeds the tolerance by 0.007 mm.
Answer: FIM = 0.057 mm; the part FAILS the total runout callout of 0.050 mm.
2. A profile of a surface callout reads 0.8 mm bilateral (equal). The true profile is a curve at a nominal radius of 25.000 mm from a center point. What are the outer and inner boundary radii?
  1. Equal bilateral zone: each side receives half the total tolerance = 0.8 ÷ 2 = 0.4 mm.
  2. Outer boundary radius = 25.000 + 0.4 = 25.400 mm.
  3. Inner boundary radius = 25.000 − 0.4 = 24.600 mm.
Answer: The tolerance zone runs from a radius of 24.600 mm to 25.400 mm — 0.4 mm on each side of the true profile.
3. A drawing uses a profile of a surface callout of 0.6 mm with a unilateral modifier (U 0.6), meaning the entire zone is placed outside the true profile. The true profile is at nominal. What are the boundaries?
  1. The full 0.6 mm is placed outside (away from the material) the true profile.
  2. Outer boundary = true profile + 0.6 mm.
  3. Inner boundary = true profile + 0.0 mm (the zone does not extend into the material side at all).
  4. Any point on the surface that falls inside the true profile or more than 0.6 mm outside is nonconforming.
Answer: The zone runs from the exact true profile to 0.6 mm outside it; nothing inside the true profile is allowed.
4. Three circular runout measurements on a shaft journal — taken at positions A, B, and C — give FIM values of 0.018 mm, 0.021 mm, and 0.019 mm. The circular runout callout is 0.025 mm. A subsequent total runout sweep gives FIM = 0.031 mm against a total runout callout of 0.025 mm. Summarize the conformance results.
  1. Circular runout at A: 0.018 ≤ 0.025 → PASS.
  2. Circular runout at B: 0.021 ≤ 0.025 → PASS.
  3. Circular runout at C: 0.019 ≤ 0.025 → PASS.
  4. Total runout: 0.031 > 0.025 → FAIL.
  5. Conclusion: all three circular slices pass independently, but the combined 3-D sweep exceeds tolerance — the shaft likely has a gradual taper or conical drift along its axis that each individual circular check missed.
Answer: Circular runout: PASS at all three positions. Total runout: FAIL (FIM 0.031 mm exceeds 0.025 mm tolerance). The part does not conform to the total runout requirement.
In class: Instructor explains profile tolerance zones (bilateral and unilateral) using a contoured template overlaid on a drawing; students interpret three profile callouts on a complex aerospace-style drawing and sketch the bilateral and unilateral zones. · Students measure total runout on a stepped shaft using a dial test indicator and V-blocks, rotating the shaft 360° and recording FIM at three axial positions; they compare FIM to the drawing callout and record a conformance decision. · Students calculate the difference between circular runout and total runout using two measurement scenarios and explain in writing why a part can pass circular runout but fail total runout.
Materials: Contoured profile template, complex drawing with profile callouts, stepped demonstration shaft, dial test indicator, V-blocks, surface plate, runout measurement log, ASME Y14.5-2018 reference
Check: Runout measurement log: FIM recorded at all three positions and conformance decision correct; profile interpretation: 3 of 3 zone sketches correct; written runout explanation assessed by instructor for technical accuracy.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NIMS Machining L1-2 — Blueprint Reading and GD&T
1. What does a profile of a surface tolerance control that profile of a line does NOT?
NIMS Machining L1-2 — Blueprint Reading and GD&T
2. A profile of a surface callout is 1.0 mm equal bilateral. The true profile radius is 30.000 mm. What is the inner boundary radius?
NIMS Machining L1-2 — Blueprint Reading and GD&T
3. During a total runout measurement, the dial test indicator reads a maximum of +0.027 mm and a minimum of −0.011 mm. What is the FIM?
NIMS Machining L1-2 — Blueprint Reading and GD&T
4. Why can a part pass circular runout at every measured position but still fail total runout?
NIMS Machining L1-2 — Blueprint Reading and GD&T
5. When measuring total runout with V-blocks on a surface plate, which features of the shaft must be placed in the V-blocks?
NIMS Machining L1-2 — Blueprint Reading and GD&T
6. The free-state symbol (F in a circle) on a GD&T callout means the measurement is taken:
NIMS Machining L1-2 — Blueprint Reading and GD&T
7. A profile callout uses a unilateral modifier (U) with the full tolerance value placed outside the true profile. Which statement correctly describes the tolerance zone?
NIMS Machining L1-2 — Safety and Health
8. Which LOTO-related safety rule applies before a machinist adjusts V-block position on a lathe bed where the lathe could be energized?
Record this lesson on my transcript. Sign in with your key and enrollment email to record lessons (enroll free if you have no key). This page stays open to read and practise.
← Previous lessonProgram planNext lesson →