Specifying Datum Features In An Order Of Precedence

Datum features must be specified in an order of precedence to position a part properly on the datum reference frame. Figure 4-2 illustrates a part where the datum features are plane surfaces. The desired order of precedence is indicated by entering the appropriate datum feature reference letters, from left to right, in the feature control frame. In Fig. 4-2(a), the datum features are identified as surfaces D, E, and F. These surfaces are most important to the design and function of the part, as...

Fig Limited Length Or Area Indication

Third Angle Projection Symbol Dimensions

Or area of a surface is to receive additional treatment or consideration within limits specified on the drawing. the extent of these limits may be indicated by use of a chain line. See Fig. 1-11. 1.7.3.1 Chain Lines. In an appropriate view or section, a chain line is drawn parallel to the surface profile at a short distance from it. Dimensions are added for length and location. If applied to a surface of revolution, the indication may be shown on one side only. See Fig. 1-11(a). 1.7.3.2...

Fig Fully Rounded Ends

For features with partially rounded ends, the radii are dimensioned. See Fig. 1-28. 1.8.5 Rounded Comers. Where corners are rounded, dimensions define the edges, and the arcs are tangent. See Fig. 1-29. 1.8.6 Outlines Consisting of Arcs. A curved outline composed of two or more arcs is dimensioned by giving the radii of all arcs and locating the necessary centers with coordinate dimensions. Other radii are located on the basis of their points of tangency. See Fig. 1-30....

LMC as Related to Positional Toleranc

Rfs Mmc Zero Tolerance Mmc

Where positional tolerancing at LMC is specified, the stated positional tolerance applies where the feature contains the least amount of material permitted by its toleranced size dimension. Specification of LMC requires perfect form at LMC. Perfect form at MMC is not required. Where the feature departs from its LMC limit of size, an increase in positional tolerance is allowed, equal to the amount of such departure. See Fig. 5-12. LMC may be specified in positional tolerancing applications...

Specifying Datum Features at LMC

Secondary Datum Plane

Where a datum feature of size is specified on an LMC basis, a primary datum may be established as the axis or center plane of the LMC boundary. A secondary or tertiary datum may be established as the axis or center plane of the true geometric counterpart of the feature's virtual condition size. See para. 2.11 and Fig. 4-17. This example illustrates both secondary and tertiary datum features specified at LMC but simulated at virtual conditions. 4.5.6 Effects of Datum Precedence and Material...

Feature Control Frame Placement

The feature control frame is related to the considered feature by one of the following methods and as depicted in Fig. 3-25 (a) locating the frame below or attached to a leader-directed callout or dimension pertaining to the feature (b) running a leader from the frame to the feature (c) attaching a side or an end of the frame to an extension line from the feature, provided it is a plane surface (d) attaching a side or an end of the frame to an extension of the dimension line pertaining to a...

Positional Tolerancing For Symmetrical Relationships

Rfs Mmc Zero Tolerance Mmc

Positional tolerancing for symmetrical relationships is that condition where the center plane of the actual mating envelope of one or more features is congruent with the axis or center plane of a datum feature within specified limits. MMC, LMC, or RFS modifiers may be specified to apply to both the tolerance and the datum feature. 5.13.1 Positional Tolerancing at MMC for As-ssmblability. A symmetrical relationship may be controlled by specifying a positional tolerance at MMC as in Fig. 5-59....

Fig Two Datum Features Single Datum Plane

Associated modifiers, separated by a dash, are entered in one compartment of the feature control frame. See para. 3.4.2 and Fig. 4-19. Since the features have equal importance, datum reference letters may be entered in any order within this compartment. 4.5.7.1 Simulation of a Single Datum Plane. Figure 4-20 is an example of a single datum plane simulated, as explained in para. 4.5.1, by simultaneously contacting the high points of two surfaces. Identification of two features to establish a...

Free State Variation

Manga Drawing Hand Manuals

Free state variation is a term used to describe distortion of a part after removal of forces applied during manufacture. This distortion is principally due to weight and flexibility of the part and the relca.sc of internal stresses resulting from fabrication. A part of this kind, for example, a pan with a very thin wall in proportion to iLs diameter, is referred to as a nonrigid pan. In some cases, it may be required that the pan meet its tolerance requirements while in the free state. See Fig....

Fig Profile Tolerancing Of A Conical Feature Datum Related

Datum Perpendicular

Ance is equal to the amount of such departure. See Figs. 6-41 and 6-42. 6.6.1.3 Tangent Plane. Where it is desired to control a feature surface established by the contacting points of that surface, the tangent plane symbol is added in the feature control frame after the stated tolerance. See Fig. 6-43. 6.6.2 Angularity. Angularity is the condition of a surface, center plane, or axis at a specified angle other than 90 from a datum plane or axis. 6.6.2.1 Angularity Tolerance. An angularity...

Hole Pattern Dimensioning

Hole Pattern Dimensioning

00.25 feature-relatinfl tolerance zone cylinders 6 zones, basically related to each other and oriented to the datum 00.25 feature-relatinfl tolerance zone cylinders 6 zones, basically related to each other and oriented to the datum Actual feature axes must simultaneously lie within both tolerance zones -00.8 pattern-locating tolerance zone cylinders 6 zones, basically related to each other, basically located to the datums Actual feature axes must simultaneously lie within both tolerance zones...

Fig Foreshortened Radii

Spherical Radius Dimensioning

Arrowhead between the radius center and the arc, it may be placed outside the arc with a leader. Where the center of a radius is not dimensionally located, the center shall not be indicated. See Fig. 1-20. 1.8.2.1 Center of Radius. Where a dimension is given to the center of a radius, a small cross is drawn at the center. Extension lines and dimension lines are used to locate the center. See Fig. 1-21. Where location of the center is unimportant, the drawing must clearly show that the arc...

Fig Profile Of A Line And Size Control

Profile Tolerance

Thecretical boundary shaped identically to the basic profile. For an internal feature, the boundary equals the MMC size of the profile minus the positional tolerance, and the entire feature surface must lie outside the boundary. For an external feature, the boundary equals the MMC size of the profile plus the positional tolerance, and the entire feature surface must lie within the boundary. To invoke this concept, the term BOUNDARY is placed beneath the positional tolerance feature control...

Bidirectional Positional Tolerancing Of Features

Bidirectional Positional Tolerance

Where it is desired to specify a greater tolerance in one direction than another, bidirectional positional tolerancing may be applied. Bidirectional positional tolerancing results in a noncylindrical tolerance zone for locating round holes therefore, the diameter symbol is omitted from the feature control frame in these applications. FIG. amp -36 NONPARALLEL HOLES INCLUDING THOSE NOT NORMAL TO SURFACE FIG. 5-37 SAME POSITIONAL TOLERANCE FOR HOLES AND COUNTERBORES, SAME DATUM REFERENCES FIG....

Zero Positional Tolerance at MMC In

The preceding explanation, a positional tolerance of some magnitude is specified for the location of features. The application of MMC permits the tolerance to exceed the value specified, provided features are within size limits, and the feature locations are such as to make the part acceptable. However, rejection of usable parts can occur where these features are actually located on or close to their true positions, but produced to a size smaller than the specified minimum outside of limits ....

Fig Different Positional Tolerance At Each End Of Long Hole

Positional Tolerance

NOTE A further refinement of perpendicularity within the positional tolerance may be required. NOTE A further refinement of perpendicularity within the positional tolerance may be required. 5.9.1 Rectangular Coordinate Method. For holes located by rectangular coordinate dimensions, separate feature control frames are used to indicate the direction and magnitude of each positional tolerance relative to specified datums. See Fig. 5-41. The feature control frames are attached to dimension lines...

May Be Applied As A Means Of Preventing An Abrupt Surface Variation Within A Relatively Short Length Of The Feature

Straightness Per Unit Length

0.1 diameter tolerance zone in each 25 mm of length The derived median line of the feature's actual local size must lie within a cylindrical tolerance zone of 0.4 diameter for the total 100 mm of length and within a 0.1 cylindrical tolerance zone for any 25 mm length, regardless of feature size. Each circular element of the surface must be within the specified limits of size. The derived median line of the feature's actual local size must lie within a cylindrical tolerance zone of 0.4 diameter...

Fig Positional Tolerancing At Mmc Relative To Datum Feature Center Planes

Positional tol-erancing is applied on an MMC, RFS, or LMC basis. When MMC or LMC is required, the appropriate modifier follows the specified tolerance and applicable datum reference in the feature control frame. See para. 2.8. 5.3.2 MMC as Related to Positional Toler-ancing. The positional tolerance and maximum material condition of mating features are considered in relation to each other. MMC by itself means a feature of a finished product contains the maximum...

Fig Positional Tolerancing Of Slots

Where a positional tolerance of a noncircular feature applies at MMC, the following apply. a In Terms of the Surfaces of a Feature. While maintaining the specified width limits of the feature, no element of its side surfaces shall be inside a theoretical boundary defined by two parallel planes equally disposed about true position and separated by a distance equal to that shown for W in Fig. 5-45. b In Terms of the Center Plane of a Feature. While maintaining...

Parts With Cylindrical Datum Features

A cylindrical datum feature is always associated with two theoretical planes intersecting at right angles on the datum axis. The datum of a cylindrical surface is the axis of the true geometric counterpart of the datum feature for example, the actual mating envelope or the virtual condition boundary , and simulated by the axis of a cylinder in the processing equipment. This axis serves as the origin of measurement from which other features of the part are located. See Figs. 4-5. 4-11, and 4-12....

Multiple Datum Reference Frames

More than one datum reference frame may be necessary for certain parts, depending upon functional requirements. In Fig. 4-24, datum features A, B, and C establish one datum reference frame, while datum features D, B, and C and datum features D, E, and B establish different datum reference frames. 4.5.11.1 Functional Datum Features. Only the required datum features should be referenced in feature control frames when specifying geometric tolerances. An understanding of the geometric control...

Runout

Runout Tolerance 0015

Runout is a composite tolcrance used to control the functional relationship of one or more features of a pan to a datum axis. 6.7.1 Runout Tolerance. The types of features controlled by runout tolerances include those surfaces constructed around a datum axis and those constructed at right angles to a datum axis. See Fig. 6-46. 6.7.1.1 Basis of Control. The datum axis is established by a diameter of sufficient length, two diameters having sufficient axial separation, or a diameter and a face at...

Calculating Positional Tolerance

True Positional Tolerance

Figure 5-9 shows a drawing for one of two identical plates to be assembled with four 14 mm maximum diameter fasteners. The 14.25 minimum diameter clearance holes are selected with a size tolerance as shown. Using conventional positional tolerancing, the required tolerance is found by the equation as given in para. B3 of Appendix B. T H - F 14.25 - 14 0.25 diameter Cylindrical tolerance zone equal to positional tolerance Axis of hole at true position Axis of hole Is Axis of hole Is located Axis...

Specifying Datum Features at MMC

Straightness Datum

Where a datum feature of size is applied on an MMC basis, machine and gaging elements in the processing equipment that remain constant in size may be used to simulate a true geometric counterpart of the feature and to establish the datum. In each case, the size of the true geometric counterpart is determined by the specified MMC limit of size of the datum feature, or its MMC virtual condition, where applicable. 4.5.4.1 Size of a Primary or Single Datum Feature. Where a primary or single datum...

Fig Symmetrical Outlines

Press Fit Tolerancing

Round holes are dimensioned as shown in Fig. 1-34. Where it is not clear that a hole goes through, the abbreviation THRU follows a dimension. The depth dimension of a blind hole is the depth of the full diameter from the outer surface of the part. Where the depth dimension is not clear, as from a curved surface, the depth should be dimensioned. For methods of specifying blind holes, see Fig. 1-34. 1.8.10 Slotted Holes. Slotted holes are dimensioned as shown in Fig. 1-35. The...

Projected Tolerance Zone

Perpendicularity Tolerance

The application of this concept is recommended where the variation in perpendicularity of threaded or press-fit holes could cause fasteners, such as screws, studs, or pins, to interfere with mating parts. See Fig. 5-31. An interference can occur where a tolerance is specified for the location of a threaded or press-fit hole, and the hole is inclined within the positional limits. Unlike the floating fastener application involving clearance holes only, the attitude of a fixed fastener is governed...

Fundamentals Of Geometric Dimensioning And Tolerancing

Figures have been revised to add a paragraph number s in the lower right corner. This notation is provided to assist users in locating the principal paragraph s that refers to the illustration. All figures have been revised, where applicable, to show the universal International Organization for Standardization ISO datum feature symbol being introduced in this issue of the Standard. All figures have been revised, where applicable, to remove the RFS symbol, which is no longer necessary. A3...

Fig Radial Hole Pattern Located By Composite Positional Tolerancing

Cad Drawing Hole Position Tolerance

FIG. 6-24 RADIAL HOLE PATTERN LOCATED BY COMPOSITE POSITIONAL TOLERANCING CONT'D Tolerance Zones for Radial Hole Pattern FIG. 6-24 RADIAL HOLE PATTERN LOCATED BY COMPOSITE POSITIONAL TOLERANCING CONT'D Tolerance Zones for Radial Hole Pattern 4X 00.6 pattern-locating tolerance zone cylinders at MMC. Pattern-locating tolerance zone framework PLTZF la located and oriented relative to datum plane A and datum axis B no rotational requirements r 4X 00.25 feature-relating tolerance zone cylinders at...

Fig Specifying Profile Of A Surface For Coplanar Surfaces

The tolerance zone thus established applies to all coplanar surfaces including datum surfaces. See Fig. 6-21. 6.5.7 Profile Tolerance for Plane Surfaces. Profile tolerancing may be used to control form and orientation of plane surfaces. In Fig. 6-22, profile of a surface is used to control a plane surface inclined to a datum feature. 6.5.8 Profile Tolerance for a Conical Feature. A profile tolerance may be specified to control the conicity of a surface in...

First Part Of

Geometric Tolerance Hole

CALLOUT MEANS THIS Datum plane A Pattern-locating tolerance zone framework PLTZF . 01 tolerance cylinders basically located and oriented relative to each other and to the specified datum reference frame. FIG. 5-22 COMPOSITE POSITIONAL TOLERANCING OF A CIRCULAR PATTERN OF FEATURES CONTD ADDITIONALLY, SECOND PART OF CALLOUT MEANS THIS One possible location and orientation of feature-relating tolerance zone framework FRTZF relative to pattern-locating tolerance zone framework PLTZF . FIG. amp -22...

Fig Spherical Radius

Where the radius dimension line is foreshortened and the center is located by coordinate dimensions, the dimension line locating the center is also foreshortened. 1.8.2.3 True Radius. Where a radius is dimension in a view that does not show the true shape of the radius, TRUE R is added before the radius dimension. See Fig. 1-24. 1.8.2.4 Multiple Radii. Where a part has a number of radii of the same dimension, a note may be used instead of dimensioning each radius...

Asme 14.5.2 -2000

FThto Foreword is not a part of ASME Y14.5M-1994. Additions, modifications, and clarification contained in this revision of ANSI Y14.5M-1982 are intended to improve national and international standardization and to harmonize the United States practices and methodology with the universal standards trend toward more efficient worldwide technical communication. Coordinating and integrating these techniques into and via computer graphics and other electronic data systems for design, manufacture,...

Circular and Cylindrical Targets

Drawing With Positional Tolerancing

Circular target lines and cylindrical target areas may be used to establish a datum axis on rotating parts. See Fig. 4-36. 4.6.5 Secondary Datum Axis. For a secondary datum feature RFS , a set of thicc equally spaccd targets may be used to establish a datum axis. See Fig. 4-37. The centering device used to establish the datum axis has a set of three equally spaced contacting features capable of moving radially at an equal rate from a common axis that is perpendicular to the primary datum plane....

Fig Datum Target Area

Figure 4-30 illustrates a part where datum target points are located by means of basic dimensions. In this example, the three mutually perpendicular planes of the datum reference frame are established by three target points on the primary datum feature, two on the secondary, and one on the tertiary. 4.6.3 Datum Planes Established by Datum Targets. A primary datum plane is established by at least three target points or areas not on a straight line. See Fig. 4-31. A...

Fig Repetitive Features

Dimensioning Slot

Where polar coordinate dimensioning is used to locate features, a linear and an angular dimension specifies a distance from a fixed point at an angular direction from two or three mutually perpendicular planes. The fixed point is the intersection of these planes. See Fig 1-51. 1.9.5 Repetitive Features or Dimensions. Repetitive features or dimensions may be specified by the use of an X in conjunction with a numeral to indicate the number of places required....

Ansi B92.2m-1980

When the following American National Standards referred to in this Standard arc superseded by a revision approved by the American National Standards Institute, Inc., the revision shall apply. American National Standards ANSI B4.2-1978, Preferred Metric Limits and Fits ANSI B5.10-1981, Machine Tapers Self Holding and Steep Taper Series ANSI ASME B46.1-1985, Surface Texture Surface Roughness, Waviness, and Lay ANSI B89.3.1-1972, Measurement of Out-of-Roundness ANSI B92.1-1970,1 Involute Splines...