Surface Finish

DRAFTING MANUAL Update 56 Update 56A. Harding* by: Bruce

Section K11.2 Page 1 February 1997*

Surface Roughness Surface Texture

1.0 INTRODUCTION

2.0 THE BASIC SYMBOL

Surface Texture Symbols, ASME/ANSI Symbols,  ASME/ANSI Y14.36M-1996, defines the American National Standard symbology for expressing desired surface finishes resulting from processing solid materials. Qualitative values can be expressed for roughness, waviness and lay. The Y14.36M  standard does not address the manufacturing processes required to produce a particular surface texture value, nor how it is verified. Surface texture definitions and texture verification methods are shown in  ASME/ANSI B46.1-1995, Surface Texture (Surface (Surface Roughness, Waviness and Lay). Representation is as shown in Figure 1.

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

While units expressed within these symbols should be consistent with the basic units expressed on the drawing, this and all newer ASME Y14 standards are illustrated with SI (metric) units. The “M” in the ASME Y14.36M designation is indicative of this, with SI units being the standard and preferred unit. However US customary units may be substituted where applicable and consistent with the principles shown. To that extent, the standard may be considered unitless. The use of surface texture symbology is optional. Where no surface texture symbology is used, the surface finish may be considered satisfactory if it is produced within the limits of size and form in accordance with ASME/ANSI Y14.5M-1994. When surface texture symbology is used, it is considered applicable to the finished surface of the object.

Basic symbol with material removal prohibited (net form)

Basic symbol with material removal required

Basic Surface Texture Symbol

2

Basic symbol with value of minimum material removal required

Figure 2. Basic surface texture symbol and variations for 1) material removal prohibited, 2) material removal allowed, and 3) material removal allowed to a minimum value

3X Text Height Expands with  text length 

Text Height (1X)

NOTES 1.6 00 00 3X Text Height Minimum +1X for each added  line of text over two 

Figure 1. ASME/ANSI Y14.36M-1995 Surface Texture Symbol Size and Proportion

1.5X Text Height 60°

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Where material removal by machining is required, a bar is added to the basic symbol over the “V.” Further refinement to the “machining required” variation may be achieved by adding a minimum material removal value to the symbol. See Figure 1. Regardless, when the basic symbol and its variants are used without values, the interpretation should be explained in a drawing note. Note that the use of the circle and bar modifiers are consistent with international symbols for “on” and “off.”

Update 56

Table 1 Preferred Series Roughness Average Values, Ra Micrometers (µm) 0.012 (0.025) (0.05) 0.075 (0.1)

.5 (1) (2) 3 (4)

0.125 0.15 (0.2) 0.25 (0.32)

5 6 (8) 10 13

(0.4) 0.5 0.63 (0.8) 1

(16) 20 25 (32) 40

1.25 (1.6) 2 2.5 (3.2)

50 (63) 80 100 (125)

4 5 (6.3) 8 10

160 200 (250) 320 400

(12.5) 15 20 (25)

(500) 600 800 (1000)

3.0 MEASUREMENT Unless otherwise specified, measurement of surface texture is accomplished 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 for specifying roughness, as defined in ASME/ANSI B 46.1-1995. It is placed above the “V” on the surface texture symbol. The preferred series roughness averages for both customary inch and metric are shown in Table 1. 4.2 Roughness Cutoff or Sampling Width is placed under the horizontal line. Standard sampling ratings are defined in ASME/ANSI B46.1, Section 9 with selection criteria listed in Section 3. Prior to the issuance of ASME/ANSI B46.1-1995, the default rating of 0.8 mm was implied if nothing was specified. This use of implied values is no longer valid. It is now mandatory that the roughness cutoff value be specifically stated on all drawings issued 6 months after the ASME/ANSI B46.1M-1995 standard was issued. Standard values for sampling width or cutoff values for both customary inch and metric 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 R z, and separated by a slash from the roughness cutoff length. Both the value and symbol must be shown. See Figures 3 and 4. 4.4 Waviness Height is the principal specification for waviness as defined in Section 1 of ASME/ANSI B46.1M1995. It is placed to the right of the cutoff value. It represents the 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.

( ) Recommended for normal use.

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

N Ra L / Rz L

Roughness Average Ra

*Supersedes issue of November 1988

Roughness Value Other than Ra

Roughness cutoff or Sampling Length Lay symbol

5.0 APPLICATION OF VALUES AND UNITS Only those values and specifications needed to verify the

Microinches (µin)

Figure 3. Parameters That May be Included in the Texture Symbol

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Table 2 Standard Sampling Length (Cutoff) Values Millimeters

Inches 0.003 0.010 0.030 0.10 0.30 1.00

0.08 0.25 0.8 2.5 8 25

6.0 SYMBOL REPLACEMENT In applying surface texture symbols on a drawing, the symbols are placed so that the point of the symbol is directly on a line representing the feature surface to be controlled, on an exten-

Roughness Average is placed above the 'V' of the symbol. The Roughness Cutoff is placed to the right and under the line. One value is maximum allowable.

1.6 2.5

1.2 0.8 2.5

Roughness Average with upper and lower limits. Units are micrometers. Material removal is allowed.

1.6 2.5

Material removal is not allowed. Surface must be produced to net Roughness Average with no secondary processing.

1.6 2.5

1.6

It is now mandatory that the Roughness Sampling Length or Cutoff rating be explicitly stated.

0.8 2.5/Rz 0.8

required surface texture characteristics should be shown in the symbol. The units shown on surface texture symbols should be the same base units as the drawing. Control values are generally indicative of the direction that generates the maximum value, usually across the lay.

Roughness Sampling Length or Cutoff for R z (2.5) when different than R a (0.8).

0.8 / Rz 0.6-0.8 Roughness parameter other than Ra can be specified as limits.

1.6 2.5

Lay specification is placed to the right of the symbol 'V'.

0.8 / SM 0.2 Maximum Roughness Spacing SM is placed to right of Cutoff rating and above lay.

NOTE X 1.6 2.5 2

Material removal allowed to a minimum 2 mm is specified to left of 'V'. "NOTE X" is used for various specifications beyond the scope of ASME/ ANSI B46.1-1995.

Figure 4. Samples of Surface Texture Applications

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Surface Roughness Surface Texture

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Ø8.1-8.2 Ø 14

12 0.8

2.5

MILL

GRIND

Example D

LAP 0.8

2.5

X

X

Y

Y A

B 0.8 A

2.5

Example C

B

Example B B

0.8

2.5

c WIDTH B

Example A

Example A illustrates a method for limiting a surface texture specification to only part of a surface. Example B illustrates the requirement that the surface must be produced with a series of processes. However it should be noted that this example is contrary to ASME/ANSI Y14.5M-1994 which advises that parts should be designed without specifying manufacturing processes,

except where such information is essential to engineering requirements. Example C uses ASME/ANSI Y14.5M-1994 symbology to constrain surface texture to areas between X and Y and A and B. Example D illustrates surface texture specifications applied to only the second of a two-step process.

Figure 5. Symbology for Special Processes and Operations *Supersedes issue of November 1988

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Figure 6. Basic Symbology Terms

Ø20

Ø10 0.8

2.5 0.8

40

Ø28

0.8

2.5

0.8

2.5

2.5

40

20 0.8 0.8

2.5

2.5

14

7 80

Figure 7. Examples of Locations for Surface Texture Symbols Note that per ASME/ANSI Y14.5M-1994, all dimensions and symbols are read from the bottom of the drawing and none are to

38

address hidden features. See Figure 8 for exception to bottom reading rule. Some dimensional information omitted for clarity.

0.8 2 SIZE SYMBOL HOLE Ø

29 B 21

HOLE FINISH

A 5 0.8 2.5

B 4 0.2 2

12 10 A

5 0

   2

   2    8  .    0

   8  .    0    0

9    5    0    1    2

   5    3

   2    4

Figure 8. Example of a Drawing with Rectangular Coordinate Dimensioning without Dimension Lines In this case dimensions and symbols may be read from the bottom and right side. This is the sole exception to the Y14.5M

requirement that dimensions be read from the bottom of a drawing.

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sion line of the surface, or on a leaderline pointing to the surface. Unless otherwise specified, the texture symbol affects the entire surface as defined by the dimensions. Where transitions from one feature to another are shown, such as fillets, rounds, and chamfers, the transitional area conforms to the roughest adjacent finish unless otherwise specified. If  practical, it is desirable for surface texture symbol to be shown in a view where the surface being controlled is shown in profile. When the feature being controlled is a diameter, the surface texture symbol may be placed directly following the diametrical dimension.

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

7.0 THE EXTENSION LEG

Figure 9. Nominal Surface Profile and Measured Surface Profile

Measured Profile

Nominal Profile

The horizontal line of the symbol, if used, should only extend to the right of the point of the symbol. See Figure 6. Texture symbols, as with other dimensions and symbols, should be oriented so that they are read from the bottom of the drawing. The exception is where the drawing is dimensioned using baseline dimensioning without dimension lines as per ASME/  ANSI Y14.5M. When baseline dimensioning is used, texture symbols, like other dimensions, are aligned to their extension lines and are read from the bottom and right side of the drawing. See Figures 7 and 8.

8.8 Nominal profile is the normal, theoretical or intended profile of the surface topology as expressed by the engineering drawing. 8.9 Peak is the highest point above the centerline and between two valleys in a roughness sampling width. It is measured perpendicular to the nominal surface. See Figure 10. 8.10 Peak-to-valley height is the sum of the maximum measurement from peak to centerline plus the maximum measurement from centerline to the valley. It is measured perpendicular to the nominal surface. See Figure 10. 8.11 Roughness is the set of fine irregularities on the surface Where surface texture symbols apply to parts involving plating of solid material. It may include flaws and tool marks caused or coating, notes or specifications should indicate if the surface by the manufacturing processes used to produce the surface. texture value applies before plating, after plating, or both. Roughness may also include traverse feed marks within the sample width. See Figure 10. 8.0 TERMINOLOGY RELATED TO SURFACE TEXTURE 8.12 Roughness Average is also known as arithmetic average (AA) and centerline average (CLA). It is the arithmetic average 8.1 Centerline is the graphical center between peaks and of the sum of the deviations, above and below the centerline of  valleys when the area of the peaks and the area of the valleys is the sample width. Deviations are measured perpendicular to the equal. centerline. The RMA (root mean average) technique is also 8.2 Cutoff is a value dictated by the response characteristics of  used and will generate different results. See Figure 10. the selected spacing limits of the roughness measuring instru8.13 Roughness sampling width is the sampling width ment. As cutoff value is a function of the measurement chosen to measure roughness characteristics separately from instrument settings and not a measured value, it does not characteristics designated as waviness. It is measured parallel require a tolerance. The chosen value should include all surface to the nominal surface. See Figure 10. irregularities being ascertained. 8.14 Surface texture is the sum total of all irregularities 8.3 Flaws are interruptions in the surface topology. They are caused by roughness, waviness, and flaws. It may be regular or unintentional, unwanted, and unexpected deviations from the random. nominal surface. Flaws often are included in roughness 8.15 Traverse width is the sampling width the stylus of the measurement. measurement instrument travels in order to generate a represen8.4 Form, Error of, is considered to be a more substantial tative sample. It is measured parallel to the nominal surface. deviation from the nominal surface but is not included in 8.16 Valley is a point of lowest depth below the centerline and surface texture. between two peaks. It is measured perpendicular to the nominal 8.5 Height is the inward or outward linear measurement which surface. See Figure 10. is perpendicular to the nominal surface. 8.17 Waviness is the more widely spaced measure of the 8.6 Lay is the orientation of tool marks or surface patterns. It surface topology. Waviness usually includes all irregularities is dictated by the production processes employed. greater than the roughness sampling width but within the 8.7 Measured profile is the profile of the surface topography waviness sampling width. Waviness may be caused by process as produced and measured by instrumentation. Within mea*Supersedes issue of November 1988

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Surface Roughness Surface Texture

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Typical T ransversin g Width

Flaws

Waviness Width

Waviness Height

Roughne ss Average Ra Peaks

Lay

Roughne ss Width

Valleys Roughne ss Sampling Length or Cu

Centerline toff

Figure 10. Surface Characteristics

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anomalies such as vibration, tool chatter, deflection, distortion, heat treatment, etc. Roughness may be thought of as being superimposed on a waviness surface. See Figure 10. 8.18 Waviness height is peak-to-valley height of the derived profile once deviations due to roughness and flaws are removed. It is measured perpendicular to the nominal surface. See Figure 10. 8.19 Waviness sampling width is the sampling width chosen to measure waviness characteristics separately from irregularities designated as roughness. It is measured parallel to the nominal surface. See Figure 10. 9.0 LAY SYMBOLS AND THEIR MEANINGS Shown in Figure 11 are the seven standard lay symbols, the definition for each, and the placement for each symbol inside the surface texture symbol. 10.0 PREFERRED SURFACE ROUGHNESS Typical surface roughness values vary widely depending on the processes employed. Even given a specific process, roughness values depend on a number of factors. For instance, surface grinding shown in Table 3 indicates a range of anywhere from 6.3 to 0.025 µm, with 1.6 to 0.10 µm in the average range. However, factors influencing the ultimate roughness value achievable include: the mechanical properties of the material itself, peripheral speed, traverse speed and feed rate of the grinding wheel, bonding material used, lubrication, and even degree of dress of the wheel. A minor change in any factor may have a profound effect on the roughness of the surface produced.

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Symbol

R

Section K11.2 Page 9 February February1997* 1997

Surface Roughness Surface Texture

Meaning Radial lay orientation relative to the center of the surface displaying the surface texture symbol.

Direction of tool marks

A

A

R Section A-A

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

A

A Section A-A

X

Angular lay orientation in both directions relative to the surface in the view displaying the surface texture symbol.

A

A

X Section A-A

M

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

A

A

M Section A-A

C

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

A

A

C Section A-A

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

A

A Section A-A

P

Particulate, non-directional, or protuberant lay orientation relative to the surface displaying the surface texture symbol.

A

A

P Section A-A

Figure 11. Lay Symbols and Their Meaning

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Table 3 Surface Roughness Produced by Common Manufacturing Processes

Micrometer (µm) >> 50 25 12.5 Microinch (µin) >> 2000 1000 500

6.3 250

3.2 125

1.6 63

0.80 0.40 0.20 0.10 0.05 0.025 0.012 32 16 8 4 2 1 .50

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 Ranges shown are typical. Higher or lower values may be obtained under special conditions. *Supersedes issue of November 1988

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Section K11.3 Page 1 July 1999

1.0 TREATMENT OF SURFACE FINISH SYMBOLOGY

2.2 Units

ISO standards are published in a different fashion than A merican National standards in that they are written as smaller focused documents (often called parts), which in turn reference other standards or other parts of the same standard. In the case of surface finish, numerous individual standards taken as a whole form a set of standards roughly comparable in scope to American National Standard ANSI/ASME Y14.36M (See Section K11.2 for complete coverage on ANSI/ASME Y14.36M). To add to the confusion of U.S. users, and unlike the numbering scheme used by ANSI, ISO standards on a particular topic often do not carry sequential numbers, nor are they in consecutive series.

Although ISO standards are expressed in metric units with commas for decimal points, in the U nited States if clearly indicated in a note, U.S. customary units could be used, as could periods (.) for decimal points. The ISO 1302 standard does not define the degrees of surface roughness and waviness or type of lay for specific purposes, nor does it specify the means by which any degree of such irregularities may be obtained or produced. Also, errors of form such as out-ofroundness and out-of-flatness are not addressed in the ISO surface finish standards. Annex sections are included in most ISO standards for clarification or informational purposes only and are not considered a part of the standards.

2.0 ISO STANDARDS

2.3 Appearance

The primary ISO standard dealing with surface finish, ISO 1302:1992 is concerned with the methods of specifying surface texture symbology and additional indications on engineering drawings. This and all ISO standards are expressed in SI metric units, with commas (,) used as decimal points. Other ISO standards are referenced for constituent provisions, but not directly discussed in the ISO 1302 standard. For instance:

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

• ISO 468:1982 Surface roughness — Parameters: Their values and general rules for specifying requirements. • ISO 4287:1997 Surface texture: Profile method — Terms, definitions and surface texture parameters. • ISO 4288:1996 Surface texture: Profile method — Rules and procedures for the assessment of surface texture. • ISO 8785:1998 Surface imperfections — Terms, definitions and parameters. • ISO 10135-1:CD Representation of parts produced by shaping processes — Part 1: Molded parts. 2.1 ISO 1302 This standard defines how surface texture and its constituents, roughness, waviness, and lay, are specified on the symbology. Surface defects are specifically excluded from consideration during inspection of surface texture. Definitions of flaws and imperfections are discussed in ISO 8785. ISO 1302 references ISO 4288:1996 specifications for precision reference specimens, roughness comparison specimens, and establishes requirements for stylus-type instruments. As with American National Standard ASME Y14.36M, ISO 1302 is not concerned with luster, appearance, color, corrosion resistance, wear resistance, hardness, sub-surface microstructure, surface integrity, and many other characteristics that may govern considerations in specific applications. The parameters in ISO surface finish standards relate to surfaces produced by abrading, casting, coating, cutting, etching, plastic deformation, sintering, wear, erosion, etc. *Purdue University West Lafayette, Indiana 47907

3.0 ISO RULES FOR COMPARING MEASURED VALUES TO SPECIFIED LIMITS 3.1 Max Rule When a maximum requirement is specified for a surface finish parameter on a drawing (e.g., Rz1.5 max), none of the inspected values may extend beyond the upper limit over the entire surface. MAX must be added to the parametric symbol in the surface finish symbology on the drawing. 3.2 16% Rule When upper and lower limits are specified, no more than 16% of all measured values of the selected parameter within the evaluation length may exceed the upper limit. No more than 16% of all measured values of the selected parameter within the evaluation length may be less than the lower limit. 3.3 Exceptions to the 16% Rule Where the measured values of roughness profiles being inspected follow a normal distribution, the 16% rule may be overridden. This is allowed when greater than 16% of the measured values exceed the upper limit, but the total roughness profile conforms with the sum of the arithmetic mean and standard deviation ( µ + s). Effectively this means that the greater the value of s, the further µ must be from the upper limit. See Figure 4.

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Basic symbol for surface under consideration or to a specification explained elsewhere in a note

Basic symbol for a surface to be machined

Production method

Roughness value in micrometers preceded by parameter symbol

Roughness value other than Ra (micrometers)

b c/f

a

e Machine allowance

In future versions of 1302, all roughness values will be allowed at location 'a' only

d

Waviness height preceded by parametric symbol or sampling length (millimeters)

Surface pattern

Basic symbol for material removal prohibited and left in the state from a previous manufacturing process

b

a2 a1

x '  x 

e

Basic symbol with all round circle added

Update 61

d ' 

c / f1 d

f2

h 

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

Chromium plated a2

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

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ISO Surface Finish Designations and Differences from ANSI

Example

Interpretation

Surface roughness is produced by milling and between upper limit of Ra = 50 µm and Ra = 6.3 µm; direction of lay is crossed in oblique directions relative to plane of projection; sampling length is 5 mm. Surface roughness of Rz = 6.3 µm is the default for all surfaces except the inside diameter which is Ra = 0.8 µm. Surface roughness is produced by grinding to Ra = 1.2 µm and limited to Ry = 6.3 max; direction of lay is perpendicular relative to the plane of projection; sampling length is 2.5 mm.

Ra 50 Ra 6,3

milled 5 X

Rz 6,3

( ) ground 2,4/Ry 6,3 MAX

Ra 1,2

Fe/Ni20pCrr Rz 1

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

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

Ra0,8

Ra 3,2

Fe/Ni10bCrr 0,8 2,5/Rz 16 2,5/Rz 6,3

   8  ,    0   a    R

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

Surface texture symbology may be applied to extended extension lines or on extended projection lines.

Ra0,8

2x45˚

  6   1 ,     R  a   3    R

R  a   0    ,8        ˚      0      4

Figure 3. Examples of ISO Applications of Surface Texture Symbology

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Rz 40

     5      4       O

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Interpretation

Update 61

Example Rz 40

3xO5

Surface texture symbology and dimensions may be combined on leader lines.

  3    R

Ra1,6

Where only one roughness symbol is shown, it is considered valid for both the extended radii and chamfers.

The symbol may be expanded with additional lines for textual information where there is insufficient room on the drawings.

Built-up surface Ground

Ground

Fe/Cr50 Ry6,2

Ry1,6

Symbology can be used for dimensional information and surface treatment.

     5      4       O

30

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

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TABLE 1 Current ISO Surface Texture Parameters Parameter

Symbol (ISO 4287:1997)

Max height profile

Rp

Max profile valley depth

Rv

Max height of profile

Rz*

Mean height of profile

Rc

Total height of profile

Rt

Arithmetic mean deviation of profile

Ra

Root mean square deviation of profile

Rq

Skewness of profile

Rsk  

Kurtosis of profile

Rku

Mean width of profile

RSm

Root mean square slope of profile

R ∆q

Material ratio of profile

Rmr

Profile section height difference

R δc

Sampling length—primary profile

lp

Sampling length—waviness profile

lw

Sampling length—roughness profile

lr

Evaluation length

ln

Ordinate value Local slope

1

Z(x) dZ/dX

Profile peak height

Zp

Profile valley depth

Zv

Profile element height

Zt

Profile element width

XL

Material length of profile

Ml

4.0 BASIC RULES FOR DETERMINING CUT-OFF WAVELENGTH When the sampling length is specified on the drawing or in documentation, the cut-off wavelength lc is equal to the sample length. When no sampling length is specified, the cut-off  wavelength is estimated using Tables 2-4. 5.0 BASIC RULES FOR MEASUREMENT OF ROUGHNESS PARAMETERS For non-periodic roughness the parameters  Ra, Rz, Rz1max or  RSm are first estimated using visual inspection, comparison to specimens, graphic analysis, etc. The sampling length is then selected from Tables 2 to 4, based on the use of  Ra, Rz,  Rz1max or RSm. Then, with instrumentation, a representative sample is taken using the sampling length chosen above.

Upper limit of surface texture parameter 

2 

1 2 

Figure 4. Roughness Parameter Value Curves Showing Mean and Standard Deviation TABLE 2 Roughness Sampling Lengths for Ra, Rq, Rsk, Rku, R∆q, and Curves for Non-periodic Profiles Such as Ground Surfaces

µm

Roughness Sampling Length (lr) mm

Roughness Evaluation Length (ln) mm

(0.006) < Ra ≤ 0.02 0.02 < Ra ≤ 0.1 0.1 < Ra ≤ 2 2 < Ra ≤ 10

0.08 0.25 0.8 2.5

0.4 1.25 4 12.5

10 < Ra ≤ 80

8

40

Ra

TABLE 3 Roughness Sampling Lengths for Rz, Rv, Rp, Rc, Rt, and Curves for Non-periodic Profiles Such as Ground Surfaces

µm

Roughness Sampling Length (Ir) mm

Roughness Evaluation Length (In) mm

(0.025) < Rz, Rz1max ≤ 0.1 0.1 < Rz, Rz1max ≤ 0.5 0.5 < Rz, Rz1max ≤ 10 10 < Rz, Rz1max ≤ 50 50 < Rz, Rz1max ≤ 200

0.08 0.25 08 2.5 8

04 1.25 4 12 5 40

Rz, Rz1max

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TABLE 4 Roughness Sampling Lengths for R-Parameters and RSm Curves for Periodic and Non-periodic Profiles

TABLE 5 Preferred Roughness Values and Roughness Grades Roughness Values Ra

µm

Roughness Sampling Length (lr) mm

Roughness Evaluation Length (ln) mm

0.013 < RSm ≤ 0.04 0.04 < RSm ≤ 013 0.13 < RSm ≤ 0.4 0.4 < RSm ≤ 1.3 1.3 < RSm ≤ 4

0.08 0.25 08 25 8

04 1.25 4 12.5 40

RSm

The measured values are then compared to the ranges of values in Tables 2 to 4 for the particular parameter. If the value is outside the range of values for the estimated sampling length, the measuring instrument is adjusted for the next higher or lower sampling length and the measurement repeated. If the final setting corresponds to that of Table 2, 3 or 4, then both the sampling length setting and  Ra, Rz, Rz1max or RSm values are correct, and a representative measurement of the parameter can be taken.

Update 61

ISO Grade Number from previous version of ISO 1302

µm

µin

50

2000

N 12

25

1000

N11

12.5

500

N10

6.3

250

N9

3.2

125

N8

1.6

63

N7

0.8

32

N6

0.4

16

N5

0.2

8

N4

0.1

4

N3

0.05

2

N2

0.025

1

N1

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

For periodic roughness, the parameter  RSm is estimated graphically, and the recommended cut-off values selected using Table 4. If the value is outside the range of values for the estimated sampling length, the measuring instrument is adjusted for the next higher or lower sampling length and the measurement repeated. If the final setting corresponds to that found in Table 4, then both the sampling length setting and

5.1 Prior Practice Prior to the adoption of current preferred roughness specification, a roughness grade was specified. This practice is now obsolete, but is still specified by some users. See Table 5 for a cross reference between preferred roughness and the prior practice using roughness grade.

Sampling Length

(lw)

(lw)

(lw)

(lw)

(lw)

Evaluation Length (ln)

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).

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