Surface Roughness Ansi vs Iso

Update 56

Section K11.2

February 1997*

DRAFTING MANUALSurface Roughness

Surface Textureby: Bruce A. Harding*Update 56

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1.0 INTRODUCTION

Surface Texture Symbols, ASME/ANSI Y14.36M-1996, definesthe American National Standard symbology for expressingdesired surface finishes resulting from processing solidmaterials. Qualitative values can be expressed for roughnewaviness and lay. The Y14.36M standard does not address thmanufacturing processes required to produce a particularsurface texture value, nor how it is verified. Surface texturedefinitions and texture verification methods are shown inASME/ANSI B46.1-1995, Surface Texture (Surface RoughnWaviness and Lay). Representation is as shown in Figure 1.

While units expressed within these symbols should be constent with the basic units expressed on the drawing, this andnewer ASME Y14 standards are illustrated with SI (metric)units. The “M” in the ASME Y14.36M designation is indica-tive of this, with SI units being the standard and preferred uHowever US customary units may be substituted whereapplicable and consistent with the principles shown. To thaextent, the standard may be considered unitless.

The use of surface texture symbology is optional. Where nosurface texture symbology is used, the surface finish may bconsidered satisfactory if it is produced within the limits of sand form in accordance with ASME/ANSI Y14.5M-1994.When surface texture symbology is used, it is consideredapplicable to the finished surface of the object.

GENIUM * Purdue University West Lafayette, Indiana 47907

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2.0 THE BASIC SYMBOL

Use of the basic surface texture symbol is indicated where thsurface may be produced by any method. If the surface is toproduced to net form (where material removal is prohibited),the circle symbol is added to the basic symbol. Examples ofthis principle include surfaces that may be produced by diecasting, forging, hot finishing, cold finishing, sintering,injection molding, or other processes where no material neebe removed for acceptable surface finishes. See Figure 2.

Figure 2. Basic surface texture symbol and variations for1) material removal prohibited, 2) material removalallowed, and 3) material removal allowed to a minimumvalue

2

Basic symbol withmaterial removalprohibited (net form)

Basic symbol withmaterial removalrequired

Basic symbol withvalue of minimummaterial removal required

BasicSurface Texture

Symbol

Figure 1. ASME/ANSIY14.36M-1995 SurfaceTexture Symbol Size andProportion

0000

1.6Text Height (1X)

60°

3X Text HeightExpands with

text length

NOTES

1.5X TextHeight

3X Text HeightMinimum

+1X for each addedline of text over two

PUBLISHING*Supersedes issue of November 1988

Update 56

The following subsection has been updated in this version: 11.2

Update 61

The following subsection has been updated in this version: 11.3

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Section K11.2February 1997*


Surface Texture

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Where material removal by machining is required, a bar isadded to the basic symbol over the “V.” Further refinementthe “machining required” variation may be achieved by adda minimum material removal value to the symbol. See Figu1. Regardless, when the basic symbol and its variants are without values, the interpretation should be explained in adrawing note. Note that the use of the circle and bar modifiare consistent with international symbols for “on” and “off.”

3.0 MEASUREMENT

Unless otherwise specified, measurement of surface texturaccomplished in the direction giving the maximum reading,usually across the lay.

4.0 PARAMETERS SHOWN IN SURFACE TEXTURE SYMBOLS

4.1 Roughness Average (Ra) is the principle parameter forspecifying roughness, as defined in ASME/ANSI B46.1-199It is placed above the “V” on the surface texture symbol. Thpreferred series roughness averages for both customary inand metric are shown in Table 1.

4.2 Roughness Cutoff or Sampling Width is placed underthe horizontal line. Standard sampling ratings are defined iASME/ANSI B46.1, Section 9 with selection criteria listed iSection 3. Prior to the issuance of ASME/ANSI B46.1-1995the default rating of 0.8 mm was implied if nothing wasspecified. This use of implied values is no longer valid. It isnow mandatory that the roughness cutoff value be specificstated on all drawings issued 6 months after the ASME/ANB46.1M-1995 standard was issued. Standard values forsampling width or cutoff values for both customary inch anmetric are shown in Table 2.

4.3 Roughness parameters other than Ra are placed un-der

the horizontal line and to the right of the cutoff rating for Rz,and separated by a slash from the roughness cutoff lengthBoththe value and symbol must be shown. See Figures 3 and 4.

4.4 Waviness Height is the principal specification forwaviness as defined in Section 1 of ASME/ANSI B46.1M-1995. It is placed to the right of the cutoff value. It representhe peak-to-valley height for waviness.

4.5 Other parameters such as evaluation length, tip radii,special ratings, etc. may be called out in a note. See Figure

5.0 APPLICATION OF VALUES AND UNITS

Only those values and specifications needed to verify the

GENIUM PU*Supersedes issue of November 1988

LLay symbol

NRa L / Rz

Roughness cutoff orSampling Length

Roughness Average Ra

Production methodology, treatment,other text, notes, callouts, etc.

Roughness ValueOther than Ra

Table 1Preferred Series Roughness Average Values, Ra

Micrometers (µm) Microinches (µin)

0.012(0.025)(0.05)0.075

(0.1)

0.1250.15

(0.2)0.25

(0.32)

(0.4)0.50.63

(0.8)1

1.25(1.6)22.5

(3.2)

45

(6.3)8

10

(12.5)1520

(25)

( ) Recommended for normal use.

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Figure 3. Parameters That May be Included in the Texture

.5(1)(2)3

(4)

56

(8)1013

(16)2025

(32)40

50(63)80

100(125)

160200

(250)320400

(500)600800

(1000)

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Section K11.2

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Surface Texture

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Table 2Standard Sampling Length (Cutoff) Values

Millimeters Inches

0.080.250.82.58

25

0.0030.0100.0300.100.301.00

GENIUM P

required surface texture characteristics should be shown insymbol. The units shown on surface texture symbols shouldthe same base units as the drawing. Control values are genally indicative of the direction that generates the maximumvalue, usually across the lay.

6.0 SYMBOL REPLACEMENT

In applying surface texture symbols on a drawing, the symbare placed so that the point of the symbol is directly on a linrepresenting the feature surface to be controlled, on an exte

Figure 4. Samples of Surface Texture Applications

1.6 2.5

1.6 2.5

1.20.8 2.5

Roughness Average isplaced above the 'V' of thesymbol. The Roughness

Cutoff is placed to the right and under theline. One value is maximum allowable.

Roughness Average withupper and lower limits.Units are micrometers.Material removal isallowed.

Material removal is notallowed. Surface must beproduced to netRoughness Average withno secondary processing.

1.6 2.5 It is now mandatory thatthe Roughness SamplingLength or Cutoff rating beexplicitly stated.

0.81.6 2.5/Rz 0.8

RoughnessSampling Lengthor Cutoff for R(2.5) when diff-erent thanR (0.8).

0.8 / Rz 0.6-0.8

Roughness parameter other than R can bespecified as limits.

1.6 2.5 Lay specification is placedto the right of thesymbol 'V'.

0.8 / SM 0.2

Maximum Roughness Spacing SM is placedto right of Cutoff rating and above lay.

NOTE X1.6 2.52

Material removalallowed to aminimum 2 mm isspecified to left of'V'. "NOTE X" is

used for various specifications beyond thescope of ASME/ ANSI B46.1-1995.

a

a

z

UBLISHING*Supersedes issue of November 1988

Update 56



Surface Texture

Example A illustrates a method for limiting a surfacetexture specification to only part of a surface. Example Billustrates the requirement that the surface must beproduced with a series of processes. However it should benoted that this example is contrary to ASME/ANSIY14.5M-1994 which advises that parts should bedesigned without specifying manufacturing processes,

Figure 5. Symbology for Special Processes and Operations

except where such information is essential to engineer-ing requirements. Example C uses ASME/ANSIY14.5M-1994 symbology to constrain surface texture toareas between X and Y and A and B. Example Dillustrates surface texture specifications applied to onlythe second of a two-step process.

c2.50.8

B

WIDTH B

2.50.8Ø8.1-8.2 Ø 14 12

Example D

2.50.8X Y

X Y

A B2.50.8

A BExample C

MILL

GRIND

LAP

Example A

Example B

GENIUM PUBLISHING*Supersedes issue of November 1988

Update 56

Section K11.2

February 1997*


Surface Texture

mity.

Note that per ASME/ANSI Y14.5M-1994, all dimensions andsymbols are read from the bottom of the drawing and none are to

address hidden features. See Figure 8 for exception to bottoreading rule. Some dimensional information omitted for clar

In this case dimensions and symbols may be read from thebottom and right side. This is the sole exception to the Y14.5M

requirement that dimensions be read from the bottom of adrawing.

Figure 6. Basic Symbology Terms

Figure 7. Examples of Locations for Surface Texture Symbols

Figure 8. Example of a Drawing with Rectangular Coordinate Dimensioning without Dimension Lines

0

10

5

12

21

29

38

0 9

15 20 35 42

A

BSIZE SYMBOL A BHOLE Ø 5 4

HOLE FINISH 0.8 2.5 0.2 2

0.8

2

0.8

2

0.8 2

Ø20

14

40

20

80

40

7

Ø28

0.8 2.5

0.8 2.5 0.8 2.5

0.8 2.5

0.8 2.5

Ø10 0.8 2.5


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Surface Texture

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sion line of the surface, or on a leaderline pointing to thesurface. Unless otherwise specified, the texture symbol affthe entire surface as defined by the dimensions. Wheretransitions from one feature to another are shown, such asfillets, rounds, and chamfers, the transitional area conformthe roughest adjacent finish unless otherwise specified. Ifpractical, it is desirable for surface texture symbol to be shin a view where the surface being controlled is shown inprofile. When the feature being controlled is a diameter, thsurface texture symbol may be placed directly following thediametrical dimension.

7.0 THE EXTENSION LEG

The horizontal line of the symbol, if used, should only exteto the right of the point of the symbol. See Figure 6. Textursymbols, as with other dimensions and symbols, should beoriented so that they are read from the bottom of the drawiThe exception is where the drawing is dimensioned usingbaseline dimensioning without dimension lines as per ASMANSI Y14.5M. When baseline dimensioning is used, textursymbols, like other dimensions, are aligned to their extenslines and are read from the bottom and right side of thedrawing. See Figures 7 and 8.

Where surface texture symbols apply to parts involving plaor coating, notes or specifications should indicate if the surtexture value applies before plating, after plating, or both.

8.0 TERMINOLOGY RELATED TO SURFACE TEXTURE

8.1 Centerline is the graphical center between peaks andvalleys when the area of the peaks and the area of the vallequal.8.2 Cutoff is a value dictated by the response characteristithe selected spacing limits of the roughness measuring insment. As cutoff value is a function of the measurementinstrument settings and not a measured value, it does notrequire a tolerance. The chosen value should include all suirregularities being ascertained.8.3 Flaws are interruptions in the surface topology. They aunintentional, unwanted, and unexpected deviations from tnominal surface. Flaws often are included in roughnessmeasurement.8.4 Form, Error of, is considered to be a more substantialdeviation from the nominal surface but is not included insurface texture.8.5 Height is the inward or outward linear measurement whis perpendicular to the nominal surface.8.6 Lay is the orientation of tool marks or surface patterns.is dictated by the production processes employed.8.7 Measured profile is the profile of the surface topographas produced and measured by instrumentation. Within mea

GENIUM PU*Supersedes issue of November 1988

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surement capability, it is a faithful representation of the actusurface. See Figure 9.

Figure 9. Nominal Surface Profile and Measured Surface Profile

Measured Profile

Nominal Profile

8.8 Nominal profile is the normal, theoretical or intendedprofile of the surface topology as expressed by the engineerdrawing.8.9 Peak is the highest point above the centerline and betwetwo valleys in a roughness sampling width. It is measuredperpendicular to the nominal surface. See Figure 10.8.10 Peak-to-valley height is the sum of the maximummeasurement from peak to centerline plus the maximummeasurement from centerline to the valley. It is measuredperpendicular to the nominal surface. See Figure 10.8.11 Roughness is the set of fine irregularities on the surfaceof solid material. It may include flaws and tool marks causedby the manufacturing processes used to produce the surfacRoughness may also include traverse feed marks within thesample width. See Figure 10.8.12 Roughness Average is also known as arithmetic averag(AA) and centerline average (CLA). It is the arithmetic averaof the sum of the deviations, above and below the centerlinethe sample width. Deviations are measured perpendicular tocenterline. The RMA (root mean average) technique is alsoused and will generate different results. See Figure 10.8.13 Roughness sampling width is the sampling widthchosen to measure roughness characteristics separately frocharacteristics designated as waviness. It is measured parato the nominal surface. See Figure 10.8.14 Surface texture is the sum total of all irregularitiescaused by roughness, waviness, and flaws. It may be regularandom.8.15 Traverse width is the sampling width the stylus of themeasurement instrument travels in order to generate a repretative sample. It is measured parallel to the nominal surface8.16 Valley is a point of lowest depth below the centerline abetween two peaks. It is measured perpendicular to the nomsurface. See Figure 10.8.17 Waviness is the more widely spaced measure of thesurface topology. Waviness usually includes all irregularitiesgreater than the roughness sampling width but within thewaviness sampling width. Waviness may be caused by proc

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Section K11.2

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Surface Texture

Figure 10. Surface Characteristics

Waviness WidthWaviness

Height

Flaws

Lay

Typical Transversing Width

Roughness Average Ra

Valleys

Peaks Roughness Width

Roughness Sampling Length or Cutoff

Centerline


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anomalies such as vibration, tool chatter, deflection, distortioheat treatment, etc. Roughness may be thought of as beingsuperimposed on a waviness surface. See Figure 10.8.18 Waviness height is peak-to-valley height of the derivedprofile once deviations due to roughness and flaws are re-moved. It is measured perpendicular to the nominal surfaceSee Figure 10.8.19 Waviness sampling width is the sampling width chosento measure waviness characteristics separately from irregulties designated as roughness. It is measured parallel to thenominal surface. See Figure 10.

9.0 LAY SYMBOLS AND THEIR MEANINGS

Shown in Figure 11 are the seven standard lay symbols, thedefinition for each, and the placement for each symbol insidthe surface texture symbol.

10.0 PREFERRED SURFACE ROUGHNESS

Typical surface roughness values vary widely depending onprocesses employed. Even given a specific process, roughnvalues depend on a number of factors. For instance, surfacegrinding shown in Table 3 indicates a range of anywhere fro6.3 to 0.025 µm, with 1.6 to 0.10 µm in the average range.However, factors influencing the ultimate roughness valueachievable include: the mechanical properties of the materiaitself, peripheral speed, traverse speed and feed rate of thegrinding wheel, bonding material used, lubrication, and evendegree of dress of the wheel. A minor change in any factor mhave a profound effect on the roughness of the surface pro-duced.


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Section K11.2

February 1997*


Surface Texture February 1997

Section A-A

CSection A-A

RSection A-A

P

XSection A-A

M

X

M

C

R

P

Radial lay orientation relative to thecenter of the surface displaying thesurface texture symbol.

Perpendicular orientation relative to thesurface in the view displaying thesurface texture symbol.

Angular lay orientation in both directionsrelative to the surface in the viewdisplaying the surface texture symbol.

Multidirectional lay orientation relative tothe surface in the view displaying thesurface texture symbol.

Circular lay orientation relative to thecenter of the surface displaying thesurface texture symbol.

Parallel lay orientation relative to thesurface in the view displaying thesurface texture symbol.

Particulate, non-directional, orprotuberant lay orientation relative to thesurface displaying the surface texturesymbol.

A A

Section A-A

A A

A A

Section A-A

A A

A A

A A

A A

Section A-A

Symbol Meaning Direction of tool marks

Figure 11. Lay Symbols and Their Meaning


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Surface Texture

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Ranges shown are typical. Higher or lower values may be obtained under special conditions.

502000

251000

12.5500

6.3250

3.2125

1.663

0.8032

0.4016

0.208

0.104

0.052

0.0251

0.012.50

Micrometer (µm) >>Microinch (µin) >>

Flame cutting

Snagging

Sawing

Planing

Shaping

Drilling

Chemical milling

EDM

Milling

Broaching

Reaming

Electron beam

Laser

Electrocheical

Boring

Turning

Barrel finishing

Electrolytic grinding

Roller burnishing

Grinding

Honing

Electropolishing

Polishing

Lapping

Superfinishing

Sand casting

Hot rolling

Forging

Perm. mold casting

Extruding

Investment casting

Cold rolling

Drawing

Die casting

Average Application

Less Frequent Application

Table 3Surface Roughness Produced by Common Manufacturing Processes

GENIUM PUBLISHINGedes issue of November 1988

DRAFTING MANUALISO Surface Finish Designations and Differences from ANSI

Update 61

Section K11.3Page 1

July 1999Update 61by B. Harding*

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1.0 TREATMENT OF SURFACE FINISH SYMBOLOGY

ISO standards are published in a different fashion than Amecan National standards in that they are written as smallerfocused documents (often called parts), which in turn refereother standards or other parts of the same standard. In the of surface finish, numerous individual standards taken as awhole form a set of standards roughly comparable in scopeAmerican National Standard ANSI/ASME Y14.36M (SeeSection K11.2 for complete coverage on ANSI/ASMEY14.36M). To add to the confusion of U.S. users, and unlikethe numbering scheme used by ANSI, ISO standards on aparticular topic often do not carry sequential numbers, nor athey in consecutive series.

2.0 ISO STANDARDS

The primary ISO standard dealing with surface finish, ISO1302:1992 is concerned with the methods of specifying surtexture symbology and additional indications on engineeringdrawings. This and all ISO standards are expressed in SI munits, with commas (,) used as decimal points. Other ISOstandards are referenced for constituent provisions, but notdirectly discussed in the ISO 1302 standard. For instance:

• ISO 468:1982 Surface roughness — Parameters: Theirvalues and general rules for specifying requirements.

• ISO 4287:1997 Surface texture: Profile method — Termsdefinitions and surface texture parameters.

• ISO 4288:1996 Surface texture: Profile method — Rulesand procedures for the assessment of surface texture.

• ISO 8785:1998 Surface imperfections — Terms, defini-tions and parameters.

• ISO 10135-1:CD Representation of parts produced byshaping processes — Part 1: Molded parts.

2.1 ISO 1302

This standard defines how surface texture and its constitueroughness, waviness, and lay, are specified on the symboloSurface defects are specifically excluded from consideratioduring inspection of surface texture. Definitions of flaws andimperfections are discussed in ISO 8785. ISO 1302 referenISO 4288:1996 specifications for precision reference speci-mens, roughness comparison specimens, and establishesrequirements for stylus-type instruments. As with AmericanNational Standard ASME Y14.36M, ISO 1302 is not con-cerned with luster, appearance, color, corrosion resistance,wear resistance, hardness, sub-surface microstructure, surintegrity, and many other characteristics that may governconsiderations in specific applications. The parameters in ISsurface finish standards relate to surfaces produced by abring, casting, coating, cutting, etching, plastic deformation,sintering, wear, erosion, etc.

GENIUM PU*Purdue University West Lafayette, Indiana 47907

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2.2 Units

Although ISO standards are expressed in metric units withcommas for decimal points, in the United States if clearlyindicated in a note, U.S. customary units could be used, ascould periods (.) for decimal points. The ISO 1302 standarddoes not define the degrees of surface roughness and wavinor type of lay for specific purposes, nor does it specify themeans by which any degree of such irregularities may beobtained or produced. Also, errors of form such as out-of-roundness and out-of-flatness are not addressed in the ISOsurface finish standards. Annex sections are included in moISO standards for clarification or informational purposes onlyand are not considered a part of the standards.

2.3 Appearance

Visually, the ISO surface finish symbol is similar to the ANSIsymbol, but the proportions of the symbol in relationship totext height differs from ANSI as do some of the parameters.See Figure 1. Surface texture characteristics may also bespecified as both “before” and “after” surface treatment. SeeFigure 2. See Table 1 for a list of all current ISO surfaceparameter symbols and Figure 3 for examples of symbologapplications.

3.0 ISO RULES FOR COMPARING MEASURED VALUES TO SPECIFIED LIMITS

3.1 Max Rule

When a maximum requirement is specified for a surface finisparameter on a drawing (e.g., Rz1.5 max), none of the in-spected values may extend beyond the upper limit over theentire surface. MAX must be added to the parametric symboin the surface finish symbology on the drawing.

3.2 16% Rule

When upper and lower limits are specified, no more than 16of all measured values of the selected parameter within theevaluation length may exceed the upper limit. No more than16% of all measured values of the selected parameter withinthe evaluation length may be less than the lower limit.

3.3 Exceptions to the 16% Rule

Where the measured values of roughness profiles beinginspected follow a normal distribution, the 16% rule may beoverridden. This is allowed when greater than 16% of themeasured values exceed the upper limit, but the total roughnprofile conforms with the sum of the arithmetic mean andstandard deviation (µ + s). Effectively this means that thegreater the value of s, the further µ must be from the upperlimit. See Figure 4.

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ISO Surface Finish Designations and Differences from ANSIUpdate 61

d

a2

f2

c / f1

b

a1

e h

d'

xx '

c / fe

Roughness valuein micrometerspreceded byparametersymbol

d

Productionmethod

Machineallowance

Surfacepattern

Roughness value other thanRa (micrometers)

In future versions of 1302, allroughness values will beallowed at location 'a' only

Waviness heightpreceded byparametric symbol orsampling length(millimeters)

ab

Basic symbol formaterial removal pro-hibited and left in thestate from a previousmanufacturingprocess

Basic symbol forsurface underconsideration orto a specificationexplained elsewherein a note

Basic symbol fora surface to bemachined

Basic symbol with allround circle added

Text height h (ISO 3098-1) 2.5 3.5 5 7 10 14 20

Line width for symbols d and d ' 0.25 0.35 0.5 0.7 1 1.2 2

Height for segment x 3.5 5 7 10 14 20 28

Height for symbol segment x ' 8 11 15 21 30 42 60

Figure 1. ISO Surface Texture Symbol and its Placement and Size Specifications

Figure 2. ISO Technique for Applying Surface Texture Symbols to Indicate Parameters Before and After Surface Treatment

Chromium plated

a1a2

Ø

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July 1999

Figure 3. Examples of ISO Applications of Surface Texture Symbology

Interpretation Example

Surface roughness is produced by milling andbetween upper limit of Ra = 50 µm and Ra = 6.3µm; direction of lay is crossed in oblique direc-tions relative to plane of projection; samplinglength is 5 mm.

Surface roughness of Rz = 6.3 µm is the defaultfor all surfaces except the inside diameter whichis Ra = 0.8 µm.

Surface roughness is produced by grinding toRa = 1.2 µm and limited to Ry = 6.3 max;direction of lay is perpendicular relative to theplane of projection; sampling length is 2.5 mm.

Surface treatment without any machining; nickel-chrome plated to Rz = 1 µm on all surfaces.

Surface is nickel-chrome plated to roughness ofRa = 3.2 µm with a sampling length of 0.8 mm;limited to Rz = 16 µm to Rz = 6.3 µm with asampling length of 2.5 mm.

Surface texture symbology may be combinedwith dimension leaders and witness (extension)lines.

Surface texture symbology may be applied toextended extension lines or on extended projec-tion lines.

Ra 50 milledRa 6,3 5

X

Rz 6,3 ( ) Ra0,8

Ra 1,2ground2,4/Ry 6,3 MAX

Fe/Ni20pCrrRz 1

Fe/Ni10bCrr

Ra 3,20,82,5/Rz 162,5/Rz 6,3

Ra0,8

Ra0

,8

2x45˚

Ra1,6

R3

Ra0,8

Rz 40

O45

40˚

GENIUM PUBLISHING



Built-up surface

Ground

Interpretation Example

Figure 3. Examples of ISO Applications of Surface Texture Symbology - continued

Surface texture symbology and dimensions maybe combined on leader lines.

Where only one roughness symbol is shown, it isconsidered valid for both the extended radii andchamfers.

The symbol may be expanded with additionallines for textual information where there isinsufficient room on the drawings.

Symbology can be used for dimensional infor-mation and surface treatment.

Rz 40

3xO5

Ra1,6R3

Fe/Cr50Ground

Ry6,2Ry1,6

30

O45

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July 1999

4.0 BASIC RULES FOR DETERMINING CUT-OFF WAVELENGTH

When the sampling length is specified on the drawing or indocumentation, the cut-off wavelength lc is equal to the samlength. When no sampling length is specified, the cut-offwavelength is estimated using Tables 2-4.

5.0 BASIC RULES FOR MEASUREMENT OF ROUGH- NESS PARAMETERS

For non-periodic roughness the parameters Ra, Rz, Rz1max orRSm are first estimated using visual inspection, comparison specimens, graphic analysis, etc. The sampling length is theselected from Tables 2 to 4, based on the use of Ra, Rz,Rz1max or RSm. Then, with instrumentation, a representativesample is taken using the sampling length chosen above.

TABLE 1Current ISO Surface Texture Parameters

SymbolParameter (ISO 4287:1997)

Max height profile Rp

Max profile valley depth RvMax height of profile Rz*

Mean height of profile Rc

Total height of profile RtArithmetic mean deviation of profile Ra

Root mean square deviation of profile Rq

Skewness of profile RskKurtosis of profile Rku

Mean width of profile RSm

Root mean square slope of profile R∆qMaterial ratio of profile Rmr

Profile section height difference Rδc

Sampling length—primary profile lpSampling length—waviness profile lw

Sampling length—roughness profile lrEvaluation length ln

Ordinate value Z(x)

Local slope dZ/dXProfile peak height Zp

Profile valley depth Zv

Profile element height ZtProfile element width XL

Material length of profile Ml

GENIUM PU

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Figure 4. Roughness Parameter Value Curves Showing Mean and Standard Deviation

TABLE 3Roughness Sampling Lengths for Rz, Rv, Rp, Rc, Rt, and

Curves for Non-periodic Profiles Such as Ground Surfaces

TABLE 2Roughness Sampling Lengths for Ra, Rq, Rsk, Rku, R∆∆∆∆∆q, andCurves for Non-periodic Profiles Such as Ground Surfaces

Roughness RoughnessRa Sampling Evaluation

Length (lr) Length (ln)µm mm mm

(0.006) < Ra ≤ 0.02 0.08 0.40.02 < Ra ≤ 0.1 0.25 1.25

0.1 < Ra ≤ 2 0.8 42 < Ra ≤ 10 2.5 12.5

10 < Ra ≤ 80 8 40

Roughness RoughnessRz, Rz1max Sampling Evaluation

Length (Ir) Length (In)µm mm mm

(0.025) < Rz, Rz1max ≤ 0.1 0.08 0 40.1 < Rz, Rz1max ≤ 0.5 0.25 1.250.5 < Rz, Rz1max ≤ 10 0 8 410 < Rz, Rz1max ≤ 50 2.5 12 550 < Rz, Rz1max ≤ 200 8 40

12

1

2

Upper limitof surfacetextureparameter

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or a

The measured values are then compared to the ranges of vin Tables 2 to 4 for the particular parameter. If the value isoutside the range of values for the estimated sampling lengtthe measuring instrument is adjusted for the next higher orlower sampling length and the measurement repeated. If thefinal setting corresponds to that of Table 2, 3 or 4, then boththe sampling length setting and Ra, Rz, Rz1max or RSm valuesare correct, and a representative measurement of the paramcan be taken.

For periodic roughness, the parameter RSm is estimatedgraphically, and the recommended cut-off values selected uTable 4. If the value is outside the range of values for theestimated sampling length, the measuring instrument isadjusted for the next higher or lower sampling length and thmeasurement repeated. If the final setting corresponds to thfound in Table 4, then both the sampling length setting and

TABLE 4Roughness Sampling Lengths for R-Parameters and RSm

Curves for Periodic and Non-periodic Profiles

Roughness RoughnessRSm Sampling Evaluation

Length (lr) Length (ln)µm mm mm

0.013 < RSm ≤ 0.04 0.08 0 40.04 < RSm ≤ 013 0.25 1.250.13 < RSm ≤ 0.4 0 8 40.4 < RSm ≤ 1.3 2 5 12.51.3 < RSm ≤ 4 8 40

GENIUM PU

TABLE 5Preferred Roughness Values and Roughness Grades

lues

h,

eter

sing

at

Roughness Values Ra ISO Grade Numberfrom previous

µm µin version of ISO 1302

50 2000 N 12

25 1000 N1112.5 500 N10

6.3 250 N9

3.2 125 N81.6 63 N7

0.8 32 N6

0.4 16 N50.2 8 N4

0.1 4 N3

0.05 2 N20.025 1 N1

RSm values are correct, and a representative measurement the parameter can be taken.

5.1 Prior Practice

Prior to the adoption of current preferred roughness specifiction, a roughness grade was specified. This practice is nowobsolete, but is still specified by some users. See Table 5 fcross reference between preferred roughness and the priorpractice using roughness grade.

Figure 5. Relationship Between Evaluation Length (ln) and Sampling Length, using Waviness (lw) as an Example. Other sampling length parameters could be: primary sampling length (lp) or roughness sampling length (lr).

SamplingLength

(lw)(lw) (lw) (lw) (lw)

Evaluation Length (ln)

BLISHING

Surface Roughness Ansi vs Iso

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