COMPARISON OF ISO 10303 PART 47 DRAFT
                                   WITH
                    ANSI AND ISO TOLERANCING STANDARDS
                                    FOR
                  HARMONIZATION AND COMPLETION OF PART 47

                               Shaw C. Feng
              National Institute of Standards and Technology
                          Gaithersburg, MD 20899

     This report provides an evaluation of the ISO 10303 Part 47 draft with respect to ANSI and ISO
     tolerancing standards.  We expect that the information contained in this report will contribute toward
     the completion and harmonization of Part 47.
          This document is the result of a comparison of the Part 47 draft with existing and developing
     U.S. and international dimensioning and tolerancing standards.  Comparison results are summarized
     in tables in each section.  The comparison of the Part 47 draft with other standards is made in basic
     tolerancing principles, size tolerance, datum and datum establishment, and geometric tolerances
     specified in standards.  Recommendations for additions and modifications to Part 47 are at the end of
     each section.  The objective is to have Part 47 completely cover the basic principles, concepts, and
     geometric tolerancing methods specified in ANSI and ISO standards.

     Key Words:     ANSI; DMIS; geometric dimensioning and tolerancing; geometric
                    tolerances; harmonization; ISO; PDES; product data; standard; standards
                    harmonization; STEP.

1 Introduction

The Standard for the Exchange of Product Model Data (STEP) is being developed as an
international standard for the computer representation of product data throughout the product's
life cycle [1].  One part of STEP, the Shape Tolerance Resource Model, contains the
information model for dimensions and tolerances of products.  The Shape Tolerance Resource
Model, also known as STEP Part 47 [2], is in the form of a draft proposal within ISO/TC
184/SC 4/WG 3/Project 3.  NIST has a strong interest in completing Part 47, while also
ensuring that it is consistent with other U.S. and international standards.

STEP Part 47 will be used in computer integrated design and manufacturing.  The purpose of
harmonizing Part 47 with existing and developing standards is to ensure that Part 47 will
completely cover all the tolerancing standards.  The goal is that users should be able to smoothly
integrate manufacturing operations that use these different standards.  STEP Part 47 is critical
to a number of activities in STEP, including development of Application Protocols for inspection
planning and process planning.  This report evaluates the content of Part 47 with respect to
several national and international standards related to geometric tolerances (one of which is
currently under development).  These tolerancing standards are for specifying allowable shape
variations of designed parts, except, one is used for the inspection of manufactured parts.  These
standards were selected because they all provide for the representation, in one form or another,
of tolerance data.

The existing standards are ANSI Y14.5 [3], ISO 1101 [4] and its family standards, and DMIS
[5].  The ISO 1101 family standards are ISO 286-1 [7], 1660 [8], 2692 [9], 5458 [10], 5459
[11], 8015 [11].  The standard under development is the Mathematical Definition of Y14.5
Dimensioning and Tolerancing Principles [6], being developed by the ASME Y14.5.1
committee.  ANSI Y14.5 and the ISO 1101 family provide definitions and drawing
representations for geometric tolerancing practice.  Y14.5.1, based on Y14.5, will provide for
rigorous and computer representable mathematical definitions of geometric tolerances.  DMIS
provides a vocabulary of terms for communicating tolerance data between computer aided design
systems and dimensional measurement equipment.  Part 47 will provide for computer
representable geometric tolerances.  The tolerances in Part 47 were created primarily based on
ANSI Y14.5M-1982 Dimensioning and Tolerancing standard with some influence from the ISO
1101 standard.

Our work toward harmonization takes place in three phases.  The first phase is to compare the
Part 47 draft with all the selected standards.  This work will allow us to tell whether Part 47
covers all the ANSI and ISO tolerancing specifications.  The second phase is to recommend
additions and modifications needed to complete Part 47.  The third phase is to generate issues
for the ISO/TC 184/SC 4/WG 3/Project 3, the IPO (IGES/PDES Organization) Tolerance
Committee, and the Y14.5.1 committee for consideration in harmonizing the two draft standards. 
This report is the result of Phase I work.

In this report, tolerancing principles, tolerance definitions, and methods for datum establishment
are listed and compared.  Section 2 compares basic tolerancing principles, the material condition
concept, and the size tolerance in Part 47 with those in other standards.  Section 3 compares
datum-related definitions and datum establishing methods in Part 47 with those in other
standards.  Section 4, 5, 6, 7 and 8 contain, respectively, comparisons of definitions of location,
orientation, form, profile, and runout tolerance in Part 47 with those in other standards.  The
recommended actions for Part 47 to have a complete coverage of these tolerances are listed at
the end of each section.  Section 9 proposes that the free state variation specified in the Y14.5
standard should be added to Part 47.  Section 10 contains concluding remarks.  Section 11
presents all the standards cited in this report.

2 Tolerancing Principles and Size Tolerances

Standard geometric tolerances are interpreted according to several fundamental concepts and
principles.  They are: the size of a feature, the concept of material condition, the maximum
material principle, the principle of independency, datum, and tolerance zones.  Tolerances are
applied to mechanical design to ensure that manufactured parts meet their functional
requirements.

ANSI Y14.5 subscribes to the maximum material principle (also called Taylor principle).  ISO
tolerancing standards adopt both the maximum material principle and the Principle of
Independency.

In this section, we review ANSI and ISO standard definitions related to size, size tolerancing,
and basic tolerancing principles adopted by the two standards.  We also compare size definitions
in the Part 47 draft with those in ANSI and ISO standards in a table of comparison.  From the
comparison, we recommend additions and modifications for Part 47.

2.1  Definitions

In ANSI Y14.5, the following definitions relate to the tolerancing principle and the size:

Envelope principle: 
     A boundary of perfect form at MMC of a feature is prescribed to control variations in
     form as well as size of the individual feature.

Maximum material condition (MMC):
     The condition in which a feature of size contains the maximum amount of material within
     the stated limits of size.

Least material condition (LMC):
     The condition in which a feature of size contains the least amount of material within the
     stated limits of size

Regardless of feature size (RFS):
     The term used to indicate that a geometric tolerance or datum reference applies at any
     increment of size of the feature within its size tolerance.

Feature of size:
     A feature associated with a size dimension.  Size dimension can be the diameter of a
     cylinder, a sphere, or the width of two parallel (opposing) planes.

Feature:
     A physical portion of a part, which needs to be distinguished from the rest of the part.

Virtual condition:
     The boundary of a feature generated in the condition that the total effect of MMC
     combined with any applicable geometric tolerances is considered.

Actual size:
     The measured size.

Limits of size:
     The specified maximum and minimum sizes of a feature.

Dimension:
     A numerical value expressed in appropriate units of measure and indicated on a drawing
     and in other documents along with lines, symbols, and notes to define the size or
     geometric characteristic, or both, of a part or part feature.

Basic dimension:
     A numerical value used to describe the theoretically exact size, profile, orientation, or
     location of a feature or datum target.  It is the basis from which permissible variations
     are established by tolerances on other dimensions, in notes, or in feature control frames.

The virtual condition establishes a boundary which combines the MMC effect with any
applicable geometric tolerance.  The surface or surfaces of the considered feature, specified at
MMC, should not vary beyond this virtual condition boundary.  Although the boundary of
perfect form at LMC is not required, the actual size of the feature must be within the limit of
the LMC size.  Similarly, if a feature is specified at LMC, the virtual condition establishes a
boundary which combines the effect of LMC with any applicable geometric tolerances.  The
surface or surfaces of the considered feature should not vary beyond this virtual condition
boundary specified at LMC.  Although the boundary of perfect form at MMC is not required,
the actual size must be within the limit of MMC size.  Specified at MMC, a feature gains
geometric tolerance, such as position and orientation, when the actual size of the feature departs
from MMC to LMC.  Similarly, specified at LMC, a feature gains geometric tolerance when
the actual size of the feature departs from LMC to MMC.  The Y14.5 standard allows
exceptions to the above rules through notes on the drawing, so that different kinds of variation
can be controlled independently.

In ISO 286-1, 2692, and 8015, the following definitions relate to tolerancing principles and size:

Principle of Independency:
     Each specified dimensional or geometrical requirement on a drawing shall be met
     independently, unless a particular relationship is specified.  Therefore, where no
     relationship is specified, the geometrical tolerance applies regardless of feature size, and
     the two requirements of size and of geometrical tolerance are treated as being unrelated.

Envelope requirement:
     The envelope of perfect form at MMC size of the feature shall not be violated.  Note that
     the envelope requirement violates the Principle of Independency.

Maximum material principle - general:
     This is a tolerancing principle which requires that the virtual condition for the toleranced
     feature(s) and, if indicated, the maximum material condition of perfect form for datum
     feature(s), shall not be violated.

Maximum material principle - applied to the tolerance feature(s):
     When applied to the toleranced feature(s), the maximum material principle permits an
     increase in the stated geometrical tolerance when the toleranced feature concerned departs
     from its maximum material condition provided that the feature does not violate the virtual
     condition.

Maximum material principle - applied to the datum feature(s);
     When the maximum material principle is applied to the datum feature(s), the datum axis
     or median plane may float in relation to the toleranced feature if there is a departure
     from the maximum material condition of the datum feature.  The value of the float is
     equal to the departure of the mating size of the datum feature from its maximum material
     size.

Maximum material condition:
     The state of the considered feature in which the feature is everywhere at that limit of size
     where the material of the feature is at its maximum.

Least material condition:
     The state of the considered feature in which the feature is everywhere at that limit of size
     where the material of the feature is at its minimum.

Virtual condition:
     The limiting boundary of perfect form permitted by the drawing data for the feature; the
     condition is generated by the collective effect of the maximum material size and the
     geometrical tolerances.

Size:
     A number expressing, in a particular unit, the numerical value of a linear dimension.

Basic (Nominal) size:
     The size from which the limits of size are derived by the application of the upper and
     lower deviations.

Limits of size:
     The two extreme permissible sizes of a feature, between which the actual size should lie,
     the limits of size being included.

Size tolerance:
     The difference between the maximum limit of size and the minimum limit of size, i.e.
     the difference between the upper deviation and the lower deviation.

Maximum limit of size:
     The greatest permissible size of a feature.

Minimum limit of size:
     The smallest permissible size of a feature.

Actual size:
     The size of a feature, obtained by measurement.

Actual local size:
     Any individual distance at any cross-section of a feature, i.e. any size measured between
     any two opposite points.

Maximum material size:
     The dimension defining the maximum material condition of a feature.

Least material size:
     The dimension defining the least material condition of a feature.

Virtual size:
     The dimension defining the virtual condition of a feature.

Mating size for an external feature:
     The dimension of the smallest perfect feature which can be circumscribed about the
     feature so that it just contacts the surface at the highest points.

Mating size for an internal feature:
     The dimension of the largest perfect feature which can be inscribed within the feature so
     that it just contacts the surface at the highest points.

The effect of the Principle of Independency is to decouple the mutual dependency of size and
form when controlling variations of a feature.  Otherwise, for ensuring mutual dependency of
size and form when controlling variations of a feature, the drawing may call for the envelope
requirement and the maximum material principle according to ISO 8015.

In DMIS, sizes are defined in terms of diameter, radius, width, and angle with two limits, uptol
and lotol (pp. 67,68,69,70 of DMIS v2.1).  The size of an ellipse is expressed by two diameters,
the long diameter and the short diameter.

In the Y14.5.1 draft, the following definitions relate to the size tolerancing:

Actual mating envelope for an external feature:
     A similar perfect feature of the smallest size which can be circumscribed about the
     feature so that it just contacts the surface at the highest points.

Actual mating envelope for an internal feature:
     A similar perfect feature of the largest size which can be inscribed within the feature so
     that it just contacts the surface at the highest points.

Actual mating size:
     The dimension of the actual mating envelope.

In the Part 47 draft, the following entities relate to the dimension and size tolerancing:

Size dimension:
     This entity include both nominal dimension and measurement of an individual feature of
     the shape of an object.  The shape of an object has the center of symmetry, i.e. a feature
     of size.  This is a supertype of the size characteristic dimension and size parameter
     dimension.

Size tolerance:
     A numerical tolerance range that constrains the variation of size dimension.

Size characteristic dimension:
     A size of a shape element that has dimensional characteristics to which a size dimension
     may be applied.

Size parameter dimension:
     A type of size dimension that specifies a value of the parameter and a tolerance on the
     parameter.  This parameter dimension specifies the nominal size of a feature.

2.2 Comparison Table

The   mark used in this section means that the standard explicitly defines or otherwise uses the
concept, the principle, size tolerance, or method indicated at the beginning of the row.

                                 Y14.5
              ISO
                              286-1/2692/8015
           Y14.5.1
   DMIS
Part 47

Principle of Independency

 

Maximum material principle
 
 
 
 
 

Envelope principle
 
 
 
 

Virtual condition
 
 
 
 

Maximum material condition
 
 
 
 
 

Least material condition
 
 
 
 
 

Regardless of feature size
 
 
 
 
 

Dimension
 
 

 
 

Basic dimension
 

 
 
 

Size

 

 
 

Nominal (Basic) size
 
 
 
 
 

Feature of size
 

 
 

Actual size (local, measured)
 
 

 

Limits of size
 
 

 
 

Size tolerance

 

 

Maximum limit of size
 
 

 
 

Minimum limit of size
 
 

 
 

Maximum material size

 

 

Least material size

 

 

Virtual size

 

Mating size for an external
feature

                                 
                

Mating size for an internal
feature

                                 
                

Actual mating envelope for
an external feature

                           
             

Actual mating envelope for
an internal feature

                           
             

2.3 Recommendations for Part 47

We recommend that the following tolerancing principles and definitions be integrated into Part
47 for its harmonization with ISO 286-1, 2692, 8015 and ANSI Y14.5 standards.

- The principle of independency
     Allow independent control of feature size and feature form.

- Virtual condition
     Allow computers to generate the boundary which simultaneously controls the variation
     of both size and form of a feature specified at MMC (or LMC).

- Virtual size
     Indicate the size of the virtual condition boundary.

- Mating envelope for an external feature
     Define the smallest perfect form that circumscribes the feature.

- Mating size for an external feature
     Define the size of the mating envelope for an external feature.

- Mating envelope for an internal feature
     Define the largest perfect form that inscribes an internal feature.

- Mating size for an internal feature
     Define the size of the mating envelope for an internal feature.

In Part 47, a size dimension is defined as "a measure of an individual feature of the shape of
an object".  We recommend that Part 47 define the dimension in a manner similar to Y14.5. 
Occasions when a dimension applies are:
     1.   A numerical value specifies the distance between two point features.  One of the features
          can be a datum feature.  A point feature can be a point in space or the center of a circle
          or a sphere.
     2.   A numerical value specifies the distance between a point feature and a line feature.  One
          of the features can be a datum feature.  A line feature can be a line element or an axis
          of another feature.
     3.   A numerical value specifies the distance between a point feature and a planar feature. 
          One can be a datum feature.  The planar feature can be a plane or a median plane.
     4.   A numerical value specifies the distance between two line features which are parallel. 
          One can be a datum feature.
     5.   A numerical value specifies the distance between a line feature and a planar feature
          which are parallel.  One of these feature can be a datum feature.
     6.   A numerical value specifies the distance between two planar features which are parallel. 
          One of these feature can be a datum feature.
     7. The size of a feature.  Size is being defined by the Y14.5.1 committee.

3 Datums

In this section, we review definitions of datums at any specified material condition and methods
for establishing a datum and a datum reference frame.

3.1 Datum-Related Definitions

In ANSI Y14.5, datum-related definitions and datum establishing methods are as follows:

Datum:
     A theoretically exact point, axis, or plane derived from the true geometric counterpart
     of a specified datum feature.  A datum is the origin from which the location, orientation,
     profile, and/or runout of features are established and measured.

Datum feature:
     A feature used to establish a datum point, axis, or plane.  A datum feature is selected on
     the basis of its geometric relationship to the toleranced feature and the requirements of
     the design.

Datum reference frame:
     Sufficient datum features are chosen to position the part in relation to a set of three
     mutually perpendicular planes, jointly called a datum reference frame.  Only three
     mutually perpendicular planes can establish a datum reference frame.  Other possibilities
     are not explored in the standard.  A datum reference frame can be established by any
     combination (important to the design, manufactured, and measurement of a part) of
     points, lines, and planes.

Datum axis establishment method:
     Specified at RFS-   The datum axis established from an internal cylinder is the axis of
                         the largest perfect cylinder that inscribes the feature.
                    or
                    The datum axis established from an external cylinder is the axis of
                    the smallest perfect cylinder that circumscribes the feature.
     Specified at MMC or LMC-  The datum axis is the axis of the feature at its
                              MMC (or LMC) size or its virtual condition as
                              applicable.

Datum plane establishment methods:
     The datum feature is a feature of size:
          Specified at RFS-   The datum plane established from an internal feature is the
                              median plane of two parallel planes that have the maximum
                              distance of separation and make contact with the datum
                              feature.
                         or
                         The datum plane established from an external feature is the
                         median plane of two parallel plans that have the minimum
                         distance of separation and make contact with the datum
                         feature.
          Specified at MMC or LMC- The datum plane is the median plane of two
                                   parallel planes that is at the MMC (or LMC)
                                   or the virtual condition of the feature.
     

     The datum feature is not a feature of size:
          A theoretical plane that makes contact with the datum feature.  If the datum
          feature is unstable (that is, it wobbles), the part may be oriented to an optimum
          position to make contact with the mating feature or a fixture.

Primary datum:
     A datum plane that is established from the primary datum feature.

Secondary datum:
     A datum plane that is established from the secondary datum feature and perpendicular
     to the primary datum plane.

Tertiary datum:
     A datum plane that is established from the tertiary datum feature and angularly oriented
     in relation to the secondary plane, such as perpendicular to both primary and secondary
     datum planes.

Compound datum:
     More than one datum feature is used to establish a single datum.  The appropriate datum
     feature reference letters, separated by a dash, are entered in one compartment of the
     feature control frame.

Pattern of features as a datum:
     Multiple features of size, such as a circular pattern of holes at MMC, may be used as
     a group to establish a datum when part function dictates.  Individual datum axes are
     established at the theoretically true position of each hole which is simulated by its virtual
     condition.

Partial surfaces as datums:
     Only part of the surface, instead of the entire surface, serves as a datum feature.  The
     partial surface is indicated by means of a thick chained line drawn parallel to the surface
     profile.

Datum target:
     A specified point, line, or area on a part used to establish a datum.

Equalizing datums:
     Where a part configuration is such that rounded features on opposite ends are used to
     establish datums, pairs of datum target points or lines are indicated on part surfaces. 
     These target points or lines coordinately dimensioned are intended for equalizing pin
     locations.

In ISO 5459, the datum related definitions and datum establishing methods are as follows:

Datum:
     A theoretically exact geometric reference (such as axes, planes, straight lines, etc.) to
     which toleranced feature are related.  Datums may be based on one or more datum
     features of a part.

Datum-system:
     A group of two or more separate datums used as a combined reference for a toleranced
     feature.

Datum feature:
     A real feature of a part (such as an edge, a surface, or a hole, etc.), which is used to
     establish the location of a datum.

Datum target:
     A point, line, or limited area on the workpiece to be used for making contact with the
     manufacturing and inspection equipment, to define the required datums in order to satisfy
     the functional requirements.

Simulated datum feature:
     A real surface of adequately precise form (such as a surface plate, a bearing, or a
     mandrel, etc.) contacting the datum feature(s) and used to establish the datum(s).

Establishing a datum plane:
     The datum feature shall be arranged in such a way that the maximum distance between
     it and the simulated datum feature has the least possible value.  If the datum feature is
     not stable with the contacting surface, suitable supports should be placed between them
     at a practical distance apart.

Establishing an axis of a cylinder:
     The datum is the axis of the largest inscribed cylinder of a hole or the smallest
     circumscribed cylinder of a shaft, so located that any possible movement of the cylinder
     in any direction is equalized.

Establishing a datum point:
     Center point of the smallest circumscribed sphere of a datum feature.

Establishing a common datum by two features:
     A common datum is established simultaneously by two datum features and is indicated
     in the third compartment of the tolerance frame by two letters separated by a hyphen.

NOTE: The largest inscribed feature or the smallest circumscribed feature are not always
uniquely found in datum features.

In Y14.5.1 draft, the datum related definitions are based on Y14.5.  A new concept of datum
establishment is proposed as follow:

Candidate datum set:
     A candidate datum set for a datum feature is the set of all datums that can be associated
     with the datum feature according to RFS, MMC, and LMC.

In DMIS, a single datum and a set of datums can be specified as:

DATDEF:
     Assign datum label to one or more previously measured feature(s).

DATSET:
     Define and activate a datum set, or part coordinate system, and assign to it a label.

In Part 47, definitions related to datum are as follows:

Simple datum:
     A datum composed of at least one and up to three dt (dimensional/tolerance) features. 
     In the case of datum targets, up to three points on a surface can be specified to define
     a datum.

Dimension/Tolerance feature:
     A categorization of things [sic] which may be the target or origin of dimension/tolerance. 
     A D/T feature corresponds to the "feature" in Y14.5.

Compound datum:
     A datum which has two [sic] references which define the datum: a primary and a co-
     reference.  A compound datum is used when two datums are equally important in the
     specification of a tolerance.

Co-reference:
     The second simple datum of a compound datum which is referenced by a tolerance.

Datum reference frame:
     A collection of from one to three datums which establish a basis for measuring the
     toleranced entity.  Each datum shall be orthogonal to the previous datums.  A material
     condition modifier may be applied to each datum, but if the datum is not present, then
     the modifier shall also be absent.

3.2 Comparison Table

The   mark used in this section means that the standard explicitly defines or otherwise uses the
concept, datum feature, or datum establishing method indicated at the beginning of the row.

                                 Y14.5
            ISO 5459
  Y14.5.1
DMIS
Part 47

Datum
 
 
 
 
 

Datum feature
 
 
 
 
 

Pattern of features as a datum
 

Partial surfaces as datums
 

Equalizing datums
 

Datum target
 
 

 

Datum reference frame
 
 
 
 
 

Establishing datum axis - MMC,
LMC
                                    
                 

Establishing datum axis - RFS
 
 

Establishing datum plane - MMC,
LMC
                                    
                 

Establishing datum plane - RFS
 
 

Establishing datum point - MMC,
LMC

                                   

Establishing datum point - RFS

 

Datum precedence (primary,
secondary, tertiary)
                           
             
      
   
 

Simulated datum feature

 

Compound (Common) datum
 
 

 
 

Partial surface as datums
 

Candidate datum set

 

3.3 Recommendations for Part 47

We recommend that the following datum definitions and datum establishment methods be added
to Part 47 for its harmonization with ISO 5459, ANSI Y14.5, and Y14.5.1 standards.

- Candidate datum set
     This set defines all the possible datums for establishing a datum using an unstable
     (wobble) datum feature.

- Datum axis establishment at MMC, LMC, and RFS
     This specification allow Part 47 to be consistent with ISO 5459 and ANSI Y14.5
     standards.

- Datum plane establishment at MMC, LMC, and RFS
     This specification will make Part 47 to be consistent with ISO 5459 and ANSI Y14.5
     standards.

- Datum point establishment at MMC, LMC, and RFS
     This specification will make Part 47 to have datum point establishment methods.

- Partial surface as datums
     This specification will allow Part 47 to be able to handle partial surface as datums.

- Pattern of features as a datum
     This specification will allow Part 47 to be able to handle pattern of features as a datum.

- Equalizing datums
     This specification will allow Part 47 to be able to handle equalizing datums.

We also recommend that Part 47 adopt the Y14.5 definition for a compound datum so that more
than two references can be used for establishing a compound datum.

4 Location Tolerances

In this section, we review position tolerances of a single feature, position tolerances of a pattern
of features, symmetry, concentricity, and coaxiality.

4.1 Location Tolerance Definitions

In ANSI Y14.5, the following definitions are related to location tolerances:

Position tolerance at RFS:
     The axis of a feature (such as cylinder, cone) or the median plane of a feature (feature
     of width) to be located within the specified position tolerance regardless of the size of
     the feature.

Position tolerance at MMC or LMC:
     The axis of a feature (such as cylinder, cone) or the median plane of a feature (feature
     of width) to be located within the specified tolerance at its MMC (or LMC).  Where the
     actual size of the feature departs from the MMC (or LMC) to LMC (or MMC),
     additional position tolerance is allowed.

Composite position tolerancing (Feature pattern location tolerancing):
     The composite tolerance controls both the larger tolerance of locations of the pattern of
     features as a group and the smaller positional tolerance for each feature within the
     pattern.

Projection tolerance zone:
     An extended portion of positional tolerance zone for a feature (such as a hole), this
     projection tolerance zone passes through its mating part (such as a fastner).

Concentricity:
     The condition where the axes of all cross-sectional elements of a surface of revolution
     are common to the axis of a datum feature.  A concentricity zone whose axis coincides
     with a datum axis and within which all cross-sectional axes of the feature being
     controlled must lie.

Symmetry:
     The condition in which a feature is symmetrically disposed about the center plane of a
     datum feature.  The symmetrical relationship is controlled by specifying a positional
     tolerance at either MMC, LMC, or RFS.

In ISO 1101, 5458 and 8015, the fundamental position tolerancing principle is that theoretically
exact dimensions and position tolerances determine the location of features, such as point, axes,
and median planes, relative to each other or in relation to one or more datums.  The tolerance
zone is symmetrically disposed about the theoretically exact location.  The maximum material
principle stated in ISO 8015 applies to location tolerances.  The location tolerancing methods
and related definitions are:

[NOTE: In the ISO 1101 standard, t equals to the tolerance, and t1 and t2 are used in a
bidirectional tolerancing situation where t1 equals to the tolerance in one direction and t2 equals
to the tolerance in the other direction.]

Position tolerance of a point:
     The tolerance zone is limited by a circle (or sphere) of diameter t, the center of which
     is in the theoretically exact position of the considered point.

Position tolerance of a line:
     The tolerance is limited by one of the three types of tolerance zones:
          -    two parallel straight lines (in two dimensions) a distance t apart disposed
               symmetrically with respect to the theoretically exact position,
          -    a parallelpiped of sections of t1 x t2, the axis of which is in the theoretically exact
               position,
          -    a cylinder of diameter of t, the axis of which is in the theoretically exact position,
     within one of these tolerance zones the axis of a feature or a line must lie.

Position tolerance of plane:
     The tolerance zone is limited by two parallel planes a distance t apart and disposed
     symmetrically with respect to the theoretically exact position of the considered surface.

Tolerance combination:
     A group of features is individually located by positional tolerancing and their pattern
     location is also located by positional tolerancing, each requirement shall be met
     independently.

Concentricity:
     The tolerance zone is limited by a circle of diameter t, the center of which coincides with
     the datum point.

Coaxiality:
     The tolerance zone is limited by a cylinder of diameter t, the axis of which coincides
     with the datum axis.

Symmetry:
     The symmetry of a feature can be specified as:
     Symmetry of a median plane:
          The tolerance zone is limited by two parallel planes a distance t apart and
          disposed symmetrically to the median plane with respect to the datum axis or
          datum plane.
     Symmetry of a line or axis:
          The tolerance zone when projected in a plane is limited by two parallel straight
          lines a distance t apart and disposed symmetrically with respect to the datum axis
          (or a datum plane) if the tolerance is specified only in one direction.
            or
          The tolerance zone is limited by a parallelpiped of section t1 x t2, the axis of
          which coincides with the datum axis if the tolerance is specified in two directions
          perpendicular to each other.

In the Y14.5.1 draft, the position tolerancing methods are the same as in Y14.5.  The shape,
size, and location of position tolerance zones are currently being mathematically defined by the
Y14.5.1 committee.

In DMIS, the position tolerancing methods are based on Y14.5, the following tolerances can be
specified:

TOL/POS:
     Specifies the position tolerance MMC, LMC, or RFS.

TOL/CORTOL:
     Specifies the bidirectional position tolerance.  This position tolerance specification is not
     based on Y14.5, but it is consistent with ISO 1101.

TOL/COMPOS:
     Specifies the composite position tolerance at MMC, LMC, or RFS for use with patterns
     to assign pattern tolerance zones and individual tolerance zones.

TOL/CONCEN:
     Specifies the concentricity tolerance.

In Part 47, the position tolerance, concentricity, and symmetry are defined as follows:

Position tolerance:
     Position tolerance is specified at MMC, LMC, or RFS referred to datum reference frame
     with spherical and cylindrical tolerance zone shapes available.  The datum reference
     frame can be composed of only one datum (the primary datum).

Concentricity:
     The tolerance specifies the diameter of cylinder center on a datum point or axis within
     which the center or axis of toleranced circular or cylindrical feature shall lie.

Symmetry:
     Symmetry tolerance defines the allowable deviation of an element of shape from a
     symmetric form about a point, curve, or surface.  Tolerance zones are cylindrical and
     spherical.

4.2 Comparison Table

The   mark used in this section means that the standard explicitly defines the position tolerance
zone indicated at the beginning of the row.

                                 Y14.5
              ISO
1101/5458/8015
                           Y14.5.
1
                                  DMIS
             Part 47

Position tolerance of a point -
Circular tolerance zone

                         

            

Position tolerance of a point -
Rectangular tolerance zone

Position tolerance of a point -
Spherical tolerance zone
                         
            

     

Position tolerance of an axis or
a line - Cylindrical  tolerance
zone
                                   
                 

        
   

Position tolerance of an axis or
a line - Two-parallel-lines
tolerance zone

                              

Position tolerance of an axis or
a line - Parallelpiped tolerance
zone

                                   

                

Position tolerance of a plane or
a median plane - Two-parallel-
planes tolerance zone
                           
             

     
  

Composite position tolerancing
 
 

 

Projection tolerance zone
 

 

Concentricity
 
 

 
 

Symmetry
 
 

 

Dimension origin tolerance
zone

                                  

Position tolerance zone defined
by a cylinder

                              

Parallelpiped position tolerance
zone by two pairs of parallel
planes

                                 

Position tolerance zone defined
by two parallel planes

                         

4.3 Recommendations for Part 47

We recommend the following actions for harmonizing Part 47 with ISO 5458 and ANSI Y14.5
standards.

- Add composite position tolerance
     In ISO 5458 and ANSI Y14.5, composite (combined) position tolerance of a pattern of
     similar features are specified.  We suggest that an entity of composite position tolerance
     be created in Part 47.

- Add bidirectional position tolerance zone
     Specified in ISO 5458, bidirectional position tolerance zone allows designers to tolerance
     the position of a point or an axis bidirectionally by defining rectangular or parallelpiped
     tolerance zones.  We suggest that this type of tolerance zone be added to the position
     tolerance entity in Part 47.

- Enhance symmetry tolerance
     We suggest that two-parallel-planes tolerance zone be added to the symmetry entity and
     two parallel planes be added to the tol_zone_shape TYPE in Part 47.

5 Orientation Tolerances

Orientation tolerances include angularity, parallelism, and perpendicularity.  In this section, we
review definitions of orientation tolerances and material conditions applied to them.

5.1 Orientation Tolerance Definitions

In ANSI Y14.5, the following definitions are related to orientation tolerances:

Angularity:
     The condition of a surface or an axis at a specified angle (other than 90o) from a datum
     plane or axis.

Angularity tolerance zone:
     A region bounded by two parallel planes with the specified distance apart at the specified
     angle (other than 90o) from a datum plane or axis, within which the surface or the axis
     of the considered feature must lie.

Parallelism:
     The condition of a surface equidistant at all points from a datum plane or an axis
     equidistant along its length to a datum axis.

Parallelism tolerance zone - two parallel planes:
     Two parallel planes or lines, with a specified distance apart and parallel to a datum plane
     or an axis, within which the line elements of the surface or axis of the considered feature
     must lie.

Parallelism zone - a cylinder:
     A cylindrical zone whose axis is parallel to a datum axis within which the axis of the
     considered feature must lie.

Perpendicularity:
     The condition of a surface, median plane, or axis at a right angle to the datum plane or
     axis.

Perpendicularity zone - two parallel planes:
     A tolerance zone defined by two parallel planes perpendicular to a datum plane or axis,
     within which the surface or median plane of the considered feature must lie.

Perpendicularity zone - a cylinder:
     A cylindrical tolerance zone perpendicular to a datum plane within which the axis of the
     considered feature must lie.

In ISO 1101, orientation tolerances are defined as follows:

Angularity of a line with reference to a datum line - line and datum line on the same plane:
     A tolerance zone is limited by two parallel lines with a distance t apart on a cutting plane
     and inclined at the specified angle to the datum line.

Angularity of a line with reference to a datum line - line and datum line on different planes:
     The tolerance zone is applied to the projection of the considered line on the plane
     containing the datum line and parallel to the considered line.

Angularity tolerance of a line with reference to a datum surface:
     The tolerance zone when projected in a plane is limited by two parallel straight lines a
     distance t apart and inclined at the specified angle to the datum surface.

Angularity tolerance of a surface with reference to a datum line:
     The tolerance zone is limited by two parallel planes a distance t apart and inclined at the
     specified angle to the datum line.

Angularity tolerance of a surface with reference to a datum surface:
     The tolerance zone is limited by two parallel planes a distance t apart and inclined at the
     specified angle to the datum surface.

Parallelism tolerance of a line with reference to a datum line - two-parallel-lines zone:
     The tolerance zone, when projected in a plane, is limited by two parallel straight lines
     a distance t apart and parallel to the datum line, if the tolerance is only specified in one
     direction.

Parallelism tolerance of a line with reference to a datum line - parallelpiped zone:
     The tolerance zone is limited by a parallelpiped of section t1 x t2 and parallel to the
     datum line if the tolerance is specified in two planes perpendicular to each other.

Parallelism tolerance of a line with reference to a datum line - cylindrical zone:
     The tolerance zone is defined by a cylinder of diameter t parallel to the datum line.

Parallelism tolerance of a line with reference to a datum surface:
     The tolerance zone is limited by two parallel planes a distance t apart and parallel to the
     datum surface.

Parallelism tolerance of a surface with reference to a datum line:
     The tolerance zone is limited by two parallel planes a distance t apart and parallel to the
     datum line.

Parallelism tolerance of a surface with reference to a datum surface:
     The tolerance zone is limited by two parallel planes a distance t apart and parallel to the
     datum surface.

Perpendicularity tolerance of a line with reference to a datum line:
     The tolerance zone when projected in a plane is limited by two parallel straight lines with
     distance t apart and perpendicular to the datum line.

Perpendicularity tolerance of a line with reference to a datum surface - two-parallel-lines zone:
     The tolerance zone when projected in a plane is limited by two parallel straight lines a
     distance t apart and perpendicular to the datum plane if the tolerance is specified only in
     one direction.

Perpendicularity tolerance of a line with reference to a datum surface - parallelpiped zone:
     The tolerance zone is limited by a parallelpiped of section t1 x t2 and perpendicular to the
     datum plane if the tolerance is specified in two directions perpendicular to each other.

Perpendicularity tolerance of a line with reference to a datum surface - cylindrical zone:
     The tolerance zone is limited by a cylinder of diameter t perpendicular to the datum
     plane.

Perpendicularity tolerance of a surface with reference to a datum line:
     The tolerance zone is limited by two parallel planes with a distance t apart and
     perpendicular to the datum line.

Perpendicularity tolerance of a surface with reference to a datum surface:
     The tolerance zone is limited by two parallel planes with a distance t apart and
     perpendicular to the datum surface.

In the current Y14.5.1 draft, angularity, perpendicularity, and parallelism tolerances are all
included in orientation tolerance.  The orientation tolerance zones are defined in a similar
manner as in Y14.5.  There are three types of zones, as follows:
     - Orientation tolerance zone bounded by two parallel planes
     - Orientation tolerance zone bounded by a cylinder
     - Orientation tolerance zone bounded by two parallel lines.

In DMIS, the orientation tolerances are specified by the angle between two features, angle
between a feature and a datum, parallelism, and perpendicularity as follows:

TOL/ANGLB:
     Specifies an angle between two features.

TOL/ANGLR:
     Specifies the angular relationship between a feature and a datum and the tolerance zone,
     within which the feature must lie, is bounded by two parallel lines, two parallel planes,
     or a cylinder.

TOL/PERP:
     Specifies the perpendicularity tolerance of a zone, within which the feature must lie,
     bounded by two parallel lines, two parallel planes, or a cylinder.

TOL/PARLEL:
     Specifies the parallelism tolerance zone, within which the feature must lie, bounded by
     two parallel lines, two parallel planes, or a cylinder parallel to the datum.

TOL/DISTB:
     specifies a distance and the distance tolerance between two features.

In Part 47, the tolerance definitions of angularity, parallelism, and perpendicularity are similar
to Y14.5 definitions.  The angularity tolerance zone is bounded by two parallel planes.  The
parallelism tolerance zone is bounded by two parallel lines, two parallel planes, or a cylinder. 
The perpendicularity tolerance zone can be bounded by a cylinder (within which a line or an axis
should lie) or a sphere (within which the locating point should lie).

5.2 Comparison Table

The   mark used in this section means that the standard explicitly defines orientation tolerance
zones indicated at the beginning of the row.

                                 Y14.5
            ISO 1101
  Y14.5.1
DMIS
Part
47

Angularity of a line to a datum
line (both are on the same
plane) - Two-parallel-lines
tolerance zone

                              

              

Angularity of a line to a datum
line (not on the same plane) -
Two-parallel-lines tolerance
zone

                                   

Angularity of a line to a datum
surface - Two-parallel-planes
tolerance zone

                              

              

Angularity of a surface to a
datum line - Two-parallel-
planes tolerance zone
                           
             

     
  

Angularity of a surface to a
datum surface - Two-parallel-
planes tolerance zone
                           
             

     
  

Parallelism of a line to a
datum line - Two-parallel-lines
tolerance zone
                              
               

      
   

Parallelism of a line to a
datum line - Cylindrical
tolerance zone
                              
               

      
   

Parallelism of a line to a
datum line - Parallelpiped
tolerance zone

                              

Parallelism of a line to a
datum surface - Two-parallel-
planes tolerance zone
                           
             

     
  

Parallelism of a surface to a
datum line - Two-parallel-
planes tolerance zone
                           
             

     
  

Parallelism of a surface to a
datum surface - Two-parallel-
planes tolerance zone
                           
             

     
  

Perpendicularity of a line to a
datum line - Two-parallel-lines
tolerance zone

                              

              

Perpendicularity of a line to a
datum surface - Two-parallel-
lines tolerance zone

                           

            

Perpendicularity of a line to a
datum surface - Parallelpiped
tolerance zone

                              

Perpendicularity of a line to a
datum surface - Cylindrical
tolerance zone
                              
               

      
   

Perpendicularity of a surface
to a datum line - Two-parallel-
planes tolerance zone
                           
             

     

Perpendicularity of a surface
to a datum surface - Two-
parallel-planes tolerance zone
                      
           

    

Orientation tolerance zone -
Two-parallel-lines

                           

Orientation tolerance zone -
Two-parallel-planes

                           

Orientation tolerance zone -
Cylindrical

                               

5.3 Recommendations for Part 47

We recommend that the following orientation tolerance zones and orientation tolerancing
methods be added to Part 47 for its harmonization with ISO 1101 and Y14.5.1.

- Angularity tolerance zone bounded by two parallel lines in the angularity entity
     This tolerance zone is specified in ISO 1101.

- Parallelism tolerance zone bounded by parallelpiped in the parallelism entity
     This tolerance zone is specified in ISO 1101.

- Perpendicularity tolerance zone bounded by two parallel lines in the perpendicularity entity
     These tolerance zone is specified in ISO 1101.

- Perpendicularity tolerance zone bounded by parallelpiped in the perpendicularity entity
     This tolerance zone is specified in ISO 1101.

- Perpendicularity tolerance zone bounded by two parallel planes in the perpendicularity entity
     This tolerance zone is specified in ISO 1101.

- Orientation tolerancing methods
     These methods specified in Y14.5.1.  We recommend that a new entity be created in Part
     47 for the orientation tolerancing methods.

6 Form Tolerances

Form tolerances include straightness, flatness, circularity (roundness), and cylindricity.  A form
tolerance is used as a refinement of the size tolerance.  Therefore, the form tolerance of a
feature should be less than the size tolerance of that feature.  Form tolerances usually do not
depend on the actual size of feature except that the straightness of an axis or the flatness of a
median plane are subject to material condition.

6.1 Form Tolerance Definitions

In Y14.5, the definitions related to form tolerances are as follows:

Straightness:
     A condition where an element of a surface or an axis of a feature is straight.  The
     straightness tolerance zone within which a line element on a surface must lie is bounded
     by two parallel lines, with a specified width, on a cutting plane that contains the line
     element.  The straightness tolerance zone of an axis is bounded by a cylinder, with a
     specified size, within which the axis should lie.

Flatness:
     A condition of a surface having all elements in one plane.  The flatness zone is bounded
     by two parallel planes, with a specified distance, within which a surface should lie.

Circularity:
     A condition of a surface of revolution where for a cylinder or cone, all points of the
     surface intersected by any plane perpendicular to a common axis are equidistant from that
     axis, for a sphere, all points of the surface intersected by any plane passing through a
     common center are equidistant from that center.

Cylindricity:
     A condition of a surface of revolution in which all points of the surface are equidistant
     from a common axis.

In ISO 1101, the definitions related to form tolerances are as follows:

Straightness tolerance defined by two parallel lines:
     The tolerance zone when projected in a plane is limited by two parallel straight lines a
     distance t apart.

Straightness tolerance defined by a parallelpiped:
     The tolerance zone is limited by a parallelpiped of section t1 x t2 if the tolerance is
     specified in two directions perpendicular to each other.

Straightness tolerance defined by a cylinder:
     The tolerance zone is limited by a cylinder of diameter t.

Flatness tolerance:
     The tolerance zone is limited by two parallel planes a distance t apart.

Circularity tolerance:
     The tolerance zone in the considered plane [NOTE: not defined] is limited by two
     concentric circles a distance t apart.

Cylindricity tolerance:
     The tolerance zone is limited by two coaxial cylinders a distance t apart.

In current Y14.5.1 draft, the mathematical definitions for straightness, flatness, and cylindricity
tolerances are defined.  The circularity tolerance is defined in the same manner as defined in
Y14.5.

In DMIS, similar to Y14.5, form tolerances are specified as follows:

TOL/CIRLTY:
     Specifies the circularity.

TOL/CYLCTY:
     Specifies the cylindricity.

TOL/FLAT:
     Specifies the flatness.

TOL/STRGHT:
     Specifies the straightness of tolerance zones bounded by two parallel lines with a
     specified width, two parallel planes (for the center plane) with a specified separation, or
     a cylinder with a specified diameter.

In Part 47 draft, straightness, circularity, cylindricity, and flatness tolerances are defined in the
same manner as defined in the Y14.5, except the straightness tolerance zone can be bounded by
two parallel lines with a specified width, two parallel planes with a specified separation, and a
cylinder with a specified diameter.

6.2 Comparison Table

The   mark used in this section means that the standard explicitly defines the form tolerance
zone indicated at the beginning of the row.

                                 Y14.5
            ISO 1101
  Y14.5.1
DMIS
Part 47

Straightness - two-parallel-lines
zone
                                   
                 
        
    
 

Straightness - parallelpiped zone

 

Straightness - two-parallel-planes
zone

                                   

                
        

Straightness - cylindrical zone
 
 
 
 
 

Flatness
 
 
 
 
 

Circularity
 
 
 
 
 

Cylindricity
 
 
 
 
 

6.3 Recommendations for Part 47

We recommend that the following form tolerance zone be added to Part 47 for its harmonization
with ISO 1101.

- Add parallelpiped straightness tolerance zone in the straightness entity
     This tolerance zone is used for bidirectionally tolerancing an axis of a feature or a line
     element of a surface.

7 Profile Tolerances

Profiles are formed by projecting a three dimensional feature onto a plane or by taking cross-
sections through the feature.  A profile is the two dimensional view of the shape in a specified
direction to an object.  The profile tolerance specifies a uniform boundary along the true profile
within which the elements of the surface must lie.  It is used to control form, or combination
of size, form, and orientation of a feature.

7.1 Profile Tolerance Definitions

In Y14.5, definitions of profile tolerance zones are as follows:

Profile of a line:
     A profile of a line tolerance zone is a two dimensional zone offset from the nominal
     surface in the normal direction, extending along the length of the considered feature or
     all around of the part.

Profile of a surface:
     A profile of a surface tolerance zone is a three dimensional zone offset from all points
     in the surface in the normal direction, extending through the length and width (or
     circumference) of the considered feature or features.

There are two types of profile tolerance zones: unilateral and bilateral.  A unilateral tolerance
zone can be either in the inside or in the outside of the feature.  Profile of a surface tolerance
requires reference to datums in order to provide proper orientation of the profile.  With profile
of a line, datums may be used to define a cross-section in the part for taking a profile.  Partial
profile control is allowed, i.e. a portion of the profile is controlled by an individual profile of
tolerance independent of other portion of the profile.

In ISO 1101 and 1660, definitions of profile tolerance zone are as follows:

Profile of a line:
     The tolerance zone is limited by two lines (curves) enveloping circles of diameter t, the
     centers of which are situated on a line having the true geometric form.

Profile of a surface:
     The tolerance zone is limited by two surfaces enveloping spheres of diameter t, the
     centers of which are situated on a surface having the true geometrical form.

In Y14.5.1, the development of the nature of the function describing boundaries of the profile
tolerance zone is in progress.

In DMIS, profile of a line tolerance and profile of a surface tolerance are specified as follows:

TOL/PROFL:
     The profile of a line tolerance specifies a tolerance zone which is a two dimensional
     band, extending along the length of the feature.  If the tolerance is unbounded, it is
     applied along the length of the feature (implies all around the part).  The tolerance zone
     may be bounded when it is desired to apply it to only a portion of the feature.

TOL/PROFS:
     The profile of a surface tolerance specifies a three dimensional tolerance zone which
     extends along the length and width or circumference of the feature.  As with the profile
     of a line tolerance, it may be bounded or unbounded.

In part 47, definitions of profile tolerances are as follows.

Profile of a line:
     The tolerance zone is formed by a circle, with the specified diameter, or its center moves
     along the design nominal curve, sweeps the region in which the feature shall lie.  The
     tolerance zone can be applied to the inside, the outside, or both sides of a feature.

Profile of a surface:
     The tolerance zone is a region bounded by ball-offset surface(s) located equally on either
     side or totally on one side of the design nominal feature, within the region the feature
     shall lie.

7.2 Comparison Table

The   mark used in this section means that the standard explicitly defines the profile tolerance
indicated at the beginning of the row.

                                 Y14.5
            ISO 1660
  Y14.5.
1
                                  DMIS
             Part 47

Profile of a line - unilateral
 

 

Profile of a line - bilateral
 
 

  
                                 (assumed)
                

Profile of a surface - unilateral
 

 

Profile of a surface - bilateral
 
 

 
                                 (assumed)
                

Partial profile control
 

7.3 Recommendations for Part 47

In Part 47, the view direction of the profile of a line is defined by a vector.  This vector also
defines the normal of the cross sectional plane which locates the profile of a part.  We propose
that Part 47 explicitly specify that the vector must be a unit vector and a point must be added
for locating the cross sectional plane in the profile entity so that the direction and the location
of the cross sectional plane are clearly defined.

We recommend that the partial profile control be added to Part 47 for its harmonization with
ANSI Y14.5.

8 Runout Tolerances

Runout tolerances are used to control the relationship of one or more features of a part to a
datum axis.  Circular runout and total runout are the two types of runout tolerance.

8.1 Runout Tolerance Definitions

In Y14.5, circular runout tolerance and total runout tolerance are defined as follows:

Circular Runout:
     Circular runout provides control of circular elements of a surface.  The tolerance is
     applied independently at any circular measuring position as the part is rotated 360o.  At
     any measuring position, each circular element of these surfaces must be within the
     specified runout tolerance when the part is rotated 360o about the datum axis.  Where
     applied to surfaces constructed around a datum axis, circular runout may be used to
     control the cumulative variations of circularity and coaxiality.  Where applied to surfaces
     constructed at right angles to the datum axis, circular runout controls wobble of a plane
     surface.

Total Runout:
     Total runout is applied simultaneously to all circular and profile measuring positions as
     the part is rotated 360o.  The entire surface must lie within the specified runout tolerance
     zone when the part is rotated 360o about the datum axis.  Where applied to surfaces
     constructed around a datum axis, total runout is used to control cumulative variations of
     circularity, straightness, coaxiality, angularity, taper, and profile of a surface.  Where
     applied to surfaces constructed at right angles to a datum axis, total runout controls
     cumulative variations of perpendicularity and flatness.

In ISO 1101, circular runout tolerance and total runout tolerance are defined as follows:

Circular Runout - radial direction:
     The tolerance zone is limited within any place of measurement perpendicular to the axis
     by two concentric circles a distance t apart, the center of which coincides with the datum
     axis.

Circular Runout - axial direction:
     The tolerance zone is limited at any radial position by two circles a distance t apart lying
     in a cylinder of measurement, the axis of which coincides with the datum axis.

Circular Runout - in any direction:
     The tolerance zone is limited within any cone of measurement, the axis of which
     coincides with the datum axis by two circles a distance t apart.

Circular Runout - in a specific direction:
     The tolerance zone is limited within any cone of measurement of the specific angle, the
     axis of which coincides with the datum axis by two circles a distance t apart.

Total Runout - radial direction:
     The tolerance zone is limited by two coaxial cylinders a distance t apart, the axes of
     which coincide with the datum axis.

Total Runout - axial direction:
     The tolerance zone is limited by two parallel planes a distance t apart and perpendicular
     to the datum axis.

In Y14.5.1, circular runout tolerance and total runout tolerance are defined as follows:

[NOTE: t0 equals to the tolerance]

Circular Runout:
     Circular runout tolerance zone is a surface of revolution generated by revolving a line
     segment about the datum axis.  The line segment is normal to the nominal surface and
     is of length t0.

Total Runout:
     Total runout tolerance is a volume of revolution generated by revolving an area about the
     datum axis.  The area is defined by two lines a distance t0 apart, normally offset from
     the nominal geometry and bounded on each side by the extent of the feature.

In DMIS, circular runout tolerance is specified in TOL/CRNOUT and the total runout tolerance
is specified in TOL/TRNOUT as follows:

TOL/CRNOUT:
     Applies to circular features which must lie within a circular area of a specified width
     around the datum axis at a specified cross section.  The tolerance is applied
     independently at any circular cross-section as the part is rotated 360o.  Both axial and
     radial direction are applicable to a feature the same manner as specified in the Y14.5.

TOL/TRNOUT:
     Applies to surfaces which must lie within a tolerance zone defined by two parallel lines
     with a specified width, two parallel planes separated by a specified distance, or two
     coaxial cylinders with a specified distance.  Total runout is used to control cumulative
     variations of a surface.  Where applied to surface constructed at right angles to a datum
     axis, total runout controls cumulative variations of perpendicularity (wobble) and flatness
     (concavity or convexity).

In Part 47, circular runout tolerance and total runout tolerance are defined as follows:

Circular Runout:
     Circular runout tolerance defines the maximum allowable deviation of position of a point
     on the toleranced feature during one complete revolution of the toleranced feature about
     the datum axis, without relative axial displacement of the measuring position.  Circular
     runout can be applied in both axial and radial directions.

Total Runout:
     Total runout specifies the maximum allowable deviation of position for all positions on
     the toleranced feature during one complete revolution of the feature about the datum axis,
     with relative axial displacement of the measuring position.  Circular runout can be
     applied in both axial and radial directions.

8.2 Comparison Table

The   mark used in this section means that the standard explicitly defines the runout tolerance
zone indicated at the beginning of the row.

                                 Y14.5
            ISO 1101
  Y14.5.1
DMIS
Part 47

Circular Runout - radial
 
 

 
 

Circular Runout - axial
 
 

 
 

Circular Runout - in any
direction

                                
                

Circular Runout - in a
specific direction

                            

Total Runout - radial
 
 
 
 
 

Total Runout - axial
 
 

 
 

Total Runout - surface
normal

                                 

8.3 Recommendations for Part 47

For more rigorous, more general, and computer representable definitions of circular runout and
total runout, we propose new definitions as:

Circular runout:
     Circular runout tolerance zone within which a circular element of a part must lie is
     bounded by an area generated by revolving a line segment with a specified length about
     the datum axis.  The orientation of the line segment can be perpendicular to the datum
     axis (in the radial direction), parallel to the datum axis (in the axial direction), or any
     other orientation with respect to the datum axis.

Total runout - Adopt the definition in Y14.5.1 as: 
     Total runout tolerance zone within which a feature must lie is bounded by a volume
     generated by revolving an area about the datum axis.  The area is bounded by two lines
     (curves) unilaterally or bilaterally generated from the normal offset of the nominal
     geometry extended along the axial direction.

These new definitions are compatible with ANSI Y14.5, Y14.5.1, ISO 1101, and DMIS.

9 Free State

Free state variation is used to describe the form distortion of a flexible part after removal of
applied forces.  These forces are primarily internal forces due to stresses resulting from
manufacturing processing, the gravitational force, and the force due to assembly.  In some cases,
a flexible part is required to meet its tolerance requirements while the part is in free state.  In
other cases, a flexible part is required to meet its tolerance requirements while it is assembled
with its mating part under certain conditions (usually the specified maximum force).

9.1 Free State Definitions

Free State Variation Tolerance:
     Specified in Y14.5, the term FREE STATE may be placed beneath the frame to clarify
     a free state requirement on a drawing containing restrained feature notes or to separate
     a free state requirement from associated features having restrained requirements.  

Specifying Tolerance on Features to be restrained:
     The restraint condition under which the tolerance is applied should be noted on drawing.

There is no free state specification in ISO, DMIS, and Part 47.

9.2 Recommendations to Part 47

We recommend that an entity for free state variation control be added to Part 47 for its
harmonization with ANSI Y14.5.

- Add the free state variation control into the tolerance model
     Create a new entity for specifying free state variation control.

- Allow a specification of restraint condition to a feature subject to free state
     Include a field for specifying restrain conditions of flexible features in the new free state
     entity.

10 Concluding Remarks

We have compared the current Part 47 draft with ISO 1101 family standards, ANSI Y14.5,
ANSI Y14.5.1 draft, and DMIS.  We have recommended actions for the ISO and IPO tolerance
committee to consider for the completeness and harmonization of Part 47 with these standards.

Different tolerancing principles have different effects on how features are toleranced.  We have
proposed that the ISO Principle of Independency be added to Part 47 for the independent control
of the size and the form of a feature.  Various size definitions specified in ISO standards are
missing from Part 47.  We have proposed that these size definitions be added to Part 47 for the
purpose of determining actual position, orientation, or form tolerances specified at maximum or
least material conditions.

We have identified all the datum establishing methods in ISO and ANSI standards that should
be included in Part 47. 

We have proposed that the composite (combined) position tolerance be added to Part 47.  This
is necessary for tolerancing a pattern of similar features, which is missing from the current Part
47 draft.  For other geometric tolerances, we have proposed that various shapes of tolerance
zones specified in ISO standards be added to Part 47 for complete coverage of current geometric
tolerances.

We plan to formalize these recommendations in another report and generate issues for the ISO
and IPO tolerance committees and the ANSI/ASME Y14.5.1 committee for harmonization of
these two standards.

11 References

[1]  ISO 10303-1, STEP Overview and Fundamentals, Draft, ISO TC 184/SC 4/WG 6,
     February 1, 1991.

[2]  ISO 10303-47, Shape Variation Tolerances, Draft, ISO TC 184/SC 4/WG 3/Project 3,
     version 2B, November 1990.

[3]  ANSI Y14.5M-1982, Dimensioning and Tolerancing, American Society of Mechanical
     Engineers, New York, NY, 1982.

[4]  ISO 1101, Technical drawings - Geometrical tolerancing - Tolerancing of form,
     orientation, location and run-out - Generalities, definitions, symbols, indications on
     drawings, International Organization for Standardization, 1983.

[5]  DMIS, Dimensional Measuring Interface Standard, ANSI/CAM-I 101, version 2.1,
     Computer Aided Manufacturing - International Inc., Arlington, TX, 1990.

[6]  ANSI Y14.5.1 Draft, Mathematical Definition of Y14.5 Dimensioning and Tolerancing
     Principles, ASME Y14.5.1 committee, April 1991.

[7]  ISO 286-1, Bases of tolerances, deviations and fits, International Organization for
     Standardization, 1988.

[8]  ISO 1660, Technical drawings - Dimensioning and tolerancing of profiles, International
     Organization for Standardization, 1988.

[9]  ISO 2692, Technical drawings - Geometrical tolerancing - Maximum material principle,
     International Organization for Standardization, 1988.

[10] ISO 5458, Technical drawings - Geometrical tolerancing - Positional tolerancing,
     International Organization for Standardization, 1987.

[11] ISO 5459, Technical drawings - Geometrical tolerancing - Datums and datum-systems
     for geometrical tolerances, International Organization for Standardization, 1981.

[12] ISO 8015, Technical drawings - Fundamental tolerancing principle, International
     Organization for Standardization, 1985.