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3.4 Feature Control Frame Placement, Combined Frames, Tolerance Zone Definition & Tabulated Tolerances

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ASME GDTP Technologist Y14.5-2009

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1 Chapter 1: Scope, Certification Logistics, Fundamental Rules & General Dimensioning

1.1 ASME GDTP Technologist Exam Scope, Prometric Logistics, & Certification Rules 1.2 Fundamental Rules of ASME Y14.5-2009 (Rules a through p) 1.3 Engineering Drawing Standards, Drawing Units, & Basic vs. Toleranced Dimensions 1.4 Dimensioning Features: Diameters, Radii, Chamfers, Countersinks, Counterbores, Spotfaces, Keyseats & Slots 1.5 Application of Dimensions & Location of Features: Lines, Leaders, Reference Dimensions, Rectangular vs. Polar Coordinates

2 Chapter 2: Features, Limits of Size, & Material Condition Principles

2.1 Features, Features of Size, & Limits of Size 2.2 Rule #1 (Taylor Principle / Envelope Rule), Its Exceptions & Overrides 2.3 Material Condition Concepts: MMC, LMC, & RFS Calculations

3 Chapter 3: General Tolerancing & Symbology

3.1 Direct Tolerancing, Limit Dimensioning, & Angular Tolerancing 3.2 The 14 Geometric Characteristic Symbols, Feature Control Frames, & Special Modifiers 3.3 Screw Threads, Gears & Splines, Angular Surfaces, Tapers & Statistical Tolerancing 3.4 Feature Control Frame Placement, Combined Frames, Tolerance Zone Definition & Tabulated Tolerances

4 Chapter 4: Datum Reference Frames & Degrees of Freedom

4.1 Theoretical Datums, Datum Feature Simulators, & Physical Datum Features 4.2 Degrees of Freedom Constraint & The 3-2-1 Datum Precedence System 4.3 Planar, Cylindrical, & Width Datum Feature Establishment

5 Chapter 5: Advanced Datum Applications: Targets, Boundary Modifiers, Customized Frames & Restrained Condition

5.1 Datum Target Points, Lines, Areas, & Movable Datum Simulators 5.2 Material Boundary Modifiers (RMB, MMB, LMB) & Datum Shift Calculations 5.3 Functional Datum Feature Selection, Multiple Datum Reference Frames & Simultaneous vs. Separate Requirements 5.4 Rotational Constraint About a Datum Axis or Point & Customized Datum Reference Frames 5.5 Irregular & Complex Datum Features, Mathematically Defined Surfaces, Restrained Condition & Datum Feature Controls

6 Chapter 6: Form Tolerances

6.1 Flatness & Straightness Controls for Surfaces & Features of Size 6.2 Circularity & Cylindricity Controls, Differences, & Inspection

7 Chapter 7: Orientation Tolerances

7.1 Parallelism Controls for Planar Surfaces & Cylindrical Features of Size 7.2 Perpendicularity & Angularity Tolerances with Basic Angles & Tangent Plane

8 Chapter 8: Location: Position Fundamentals & Calculations

8.1 Position Tolerancing Fundamentals, True Position, & Coordinate Conversions 8.2 Bonus Tolerance & Virtual Condition Calculations for Internal & External Features 8.3 Projected Tolerance Zones (Ⓟ Modifier) & Fixed vs. Floating Fastener Formulas 8.4 Zero Positional and Orientation Tolerancing at MMC and at LMC 8.5 Surface vs. Axis Interpretation of Position & the Boundary Concept for Slots, Tabs & Noncircular Features

9 Chapter 9: Location: Patterns, Composite Controls, Coaxial & Symmetrical Relationships, and Functional Gaging

9.1 Hole & Slot Patterns, Multi-Segment Frames, & Composite Position Tolerancing 9.2 Functional Gaging Principles & Inspection Verification of Position 9.3 Coaxial Holes, Counterbored Holes, Non-Parallel Axes, Spherical Features & Bidirectional Position 9.4 Concentricity & Symmetry Tolerances Under ASME Y14.5-2009 9.5 LMC Applied to Position: Wall Thickness, Breakout Protection & Boundary Calculations

10 Chapter 10: Profile Tolerances

10.1 Profile of a Line & Profile of a Surface Fundamentals & Basic Geometry 10.2 Bilateral, Unilateral, & Unequally Disposed Profile Boundaries (Ⓤ Modifier) 10.3 Composite Profile Tolerances vs. Multiple Single-Segment Profile Controls 10.4 Profile Verification, Coplanarity Controls, & Non-Rigid Parts 10.5 Profile Applications: Conicity, Extruded and Irregular Shapes, and Profile-Controlled Datum Features 10.6 Modifier Rules for Profile & Combined Controls (Profile with Position, Orientation and Runout)

11 Chapter 11: Runout Tolerances & Comparative Control Analysis

11.1 Circular Runout vs. Total Runout Interpretation & Dial Indicator Verification 11.2 Comparative Analysis: Runout vs. Form, Orientation, & Concentricity Controls

3.4 Feature Control Frame Placement, Combined Frames, Tolerance Zone Definition & Tabulated Tolerances

Key Takeaways Explain This Topic AI

ASME Y14.5-2009 para. 3.6 requires the diameter or spherical diameter symbol to precede the tolerance value only where the zone is a cylinder or sphere; without it the value is the distance between two parallel straight lines or planes or two uniform boundaries.

A composite feature control frame (para. 3.4.4) uses a single entry of the geometric characteristic symbol, restricted to position or profile, while two single-segment frames (para. 3.4.5) repeat the symbol in each row and create independent requirements.

Where a single datum is established by two or more datum features, all datum feature reference letters separated by a dash go in one compartment, such as A-B (para. 3.4.2).

Para. 3.5 lists five permitted ways to attach a feature control frame, and attaching it to an extension line of a plane surface controls the surface while attaching it to an extension of a size dimension line controls the feature of size.

Tabulated tolerances are entered as a letter preceded by the abbreviation TOL (para. 3.7), and para. 3.2 permits a supplementary note wherever symbology alone cannot convey the requirement.

Last updated: September 2026

3.4 Feature Control Frame Placement, Combined Frames, Tolerance Zone Definition & Tabulated Tolerances

Quick Answer: Section 3 of ASME Y14.5-2009 does more than list symbols — paras. 3.4 through 3.7 define how a feature control frame is built, attached, read, and abbreviated . The five permitted placement methods are enumerated in para. 3.5 and Fig. 3-29. Para. 3.6 supplies the single most consequential reading rule on the exam: where the tolerance value represents the diameter of a cylindrical or spherical zone, the diameter or spherical diameter symbol shall precede the tolerance value; where the zone is other than a diameter, the diameter symbol is omitted and the value represents the distance between two parallel straight lines or planes, or between two uniform boundaries. Para. 3.7 allows a tabulated tolerance letter preceded by the abbreviation TOL , and para. 3.2 permits a note where symbology alone cannot convey the requirement.

Building the Frame (Paras. 3.4.1 – 3.4.3)

A feature control frame is a rectangle divided into compartments containing the geometric characteristic symbol, followed by the tolerance value or description, modifiers, and any applicable datum feature references. ┌─────┬──────────────────┬────────┬────────┬────────┐

  • │ ⌖ │ ⌀ 0.25 Ⓜ Ⓟ 18 │ A │ B Ⓜ │ C │
  • └─────┴──────────────────┴────────┴────────┴────────┘
  • 1 2 3 4 5
  • 1 Geometric characteristic symbol
  • 2 Diameter/spherical-diameter symbol (if the zone is diametral),
  • tolerance value, material condition modifier, projected zone symbol + height
  • 3-5 Datum feature references in ORDER OF PRECEDENCE, each optionally
  • followed by a MATERIAL BOUNDARY modifier (Ⓜ = MMB, Ⓛ = LMB)

3.4.2 — one datum feature reference : the datum feature reference letter goes in a compartment following the tolerance , optionally followed by a material boundary modifier. Where a single datum is established by two or more datum features — for example, an axis established from two coaxial diameters — all of the datum feature reference letters, separated by a dash, are entered in a single compartment ( A-B ).

3.4.3 — two or three datum feature references : each letter, followed where applicable by its material boundary modifier, is entered in a separate compartment in order of precedence , not alphabetical order. | C | A | B | is a perfectly legal frame in which C is primary.

Multi-Segment Frames: Composite vs. Two Single-Segment (Paras. 3.4.4 – 3.4.5)

Construction Para. Symbol Layout Meaning

Composite feature control frame 3.4.4 One entry of the geometric characteristic symbol ( position or profile only ) spanning both rows Lower segment refines per paras. 7.5.1 / 8.6 — datums constrain orientation only

Two single-segment feature control frames 3.4.5 The symbol is repeated in each row Each row is an independent requirement per para. 7.5.2 — lower-segment datums constrain orientation and location

The one-glance test: count the geometric characteristic symbols. One symbol spanning both rows = composite. Two symbols, one per row = two single-segment frames. Everything else about the interpretation follows from that single visual difference, and the standard restricts composite construction to position and profile .

Combined Frame and Datum Feature Symbol (Para. 3.4.6)

Where a feature or pattern of features that is controlled by a geometric tolerance also serves as a datum feature , the feature control frame and the datum feature symbol may be combined — the datum feature symbol is attached to the frame. This is how a drawing says "these four holes are located to A and B, and the resulting pattern is datum feature C."

Projected Tolerance Zone in the Frame (Para. 3.4.7)

Where a positional or orientation tolerance is specified as a projected tolerance zone, the projected tolerance zone symbol shall be placed in the feature control frame along with the dimension indicating the minimum height of the zone , following the stated tolerance and any modifier. Where clarification is needed, the projected zone is shown with a chain line and the minimum height dimensioned in a drawing view — in which case the height may be omitted from the frame .

Placement of the Frame (Para. 3.5)

The frame is related to the considered feature by one of the following methods, all shown in Fig. 3-29:

Locating the frame below or attached to a leader-directed note or dimension pertaining to the feature.

Attaching a leader from the frame pointing to the feature.

Attaching a side, corner, or end of the frame to an extension line from the feature , provided it is a plane surface .

Attaching a side, corner, or end of the frame to an extension of the dimension line pertaining to a feature of size.

Placing the frame in a note, chart, or the general tolerance block.

The distinction that matters for interpretation is method 3 versus method 4: an extension line from a plane surface means the control applies to the surface ; an extension of the dimension line of a feature of size means the control applies to the feature of size and therefore to its derived axis or center plane.

Defining the Tolerance Zone (Para. 3.6) — The Diameter Symbol Rule

Where the specified tolerance value represents the diameter of a cylindrical or spherical zone , the diameter or spherical diameter symbol shall precede the tolerance value . Where the tolerance zone is other than a diameter , the diameter symbol shall be omitted , and the specified value represents the distance between two parallel straight lines or planes, or the distance between two uniform boundaries , as the case may be. Some zones are nonuniform and are specified by other means (see para. 8.3.2).

  • Callout Zone Geometry Typical Application
  • ⌖ ⌀0.25 Ⓜ A B C Cylinder , ⌀0.25 Round hole located in two directions
  • ⌖ 0.25 A B C Two parallel planes , 0.25 apart Slot or tab center plane; bidirectional position (para. 7.4.4)
  • ⌖ S⌀0.25 A B C Sphere , S⌀0.25 Spherical feature (para. 7.4.6)
  • ⏥ 0.05 Two parallel planes, 0.05 apart Surface flatness
  • ⌭ 0.1 Two coaxial cylinders, 0.1 radial separation Cylindricity

Why examiners love this rule: a stem shows ⌖ 0.4 | A | B | C on a round hole and asks for the zone. The absent diameter symbol means the zone is two parallel planes 0.4 apart , not a ⌀0.4 cylinder — a bidirectional control. Nothing about the feature being round overrides the frame.

Tabulated Tolerances and Supplementary Notes (Paras. 3.7 and 3.2)

3.7 Tabulated tolerances : where the tolerance in a feature control frame is tabulated, a letter representing the tolerance, preceded by the abbreviation TOL , shall be entered in the frame — for example ⌖ | ⌀ TOL A | A | B | C , with the value of TOL A supplied in a table. This is standard practice on tabulated part families where one drawing covers several dash numbers.

3.2 Use of notes to supplement symbols : situations arise where the desired geometric requirements cannot be completely conveyed by symbology . In such cases a note may be used to describe the requirement, either separately or to supplement a geometric symbol . SEP REQT , EACH ELEMENT , TWO SURFACES , and thread-feature designations such as MAJOR DIA all rely on this permission.