Update 56
Update 56
Surface Texture
Surface Texture
February 1997*February 1997* by: Bruce A. Harding*by: Bruce A. Harding*
1.0 INTRODUCTION 1.0 INTRODUCTION Surface Texture Symbols,
Surface Texture Symbols, ASME/ANSI Y14.36M-1996, ASME/ANSI Y14.36M-1996,definesdefines the American National Standard symbology for expressing the American National Standard symbology for expressing desired surface finishes resulting from
desired surface finishes resulting from processing solidprocessing solid materials. Qualitative values can be expressed for roughness, materials. Qualitative values can be expressed for roughness, waviness and lay. The
waviness and lay. The Y14.36M Y14.36M standard does not address thestandard does not address the manufacturing processes required to produce a particular manufacturing processes required to produce a particular surface texture value, nor how
surface texture value, nor how it is verified. Surface textureit is verified. Surface texture definitions and texture verification methods are shown in definitions and texture verification methods are shown in ASME/ANSI B46.1-1995, Surface Texture (Surf
ASME/ANSI B46.1-1995, Surface Texture (Surface Roughness,ace Roughness, Waviness and Lay).
Waviness and Lay).Representation is as shown in Figure 1.Representation is as shown in Figure 1. While units expressed within these symbols should be
While units expressed within these symbols should be consis- consis-tent with the basic units expressed on the drawing, this and all tent with the basic units expressed on the drawing, this and all newer ASME Y14
newer ASME Y14 standards are illustrated with SI (metric)standards are illustrated with SI (metric) units. The “M” in the ASME Y14.36M designation is units. The “M” in the ASME Y14.36M designation is indica-tive of this, with SI units being the standard and preferred unit. tive of this, with SI units being the standard and preferred unit. However US customary units may
However US customary units may be substituted wherebe substituted where applicable and consistent with the principles shown. To applicable and consistent with the principles shown. To thatthat extent, the standard may be
extent, the standard may be considered unitless.considered unitless.
The use of surface texture symbology is optional. Where no The use of surface texture symbology is optional. Where no surface texture symbology is used, the
surface texture symbology is used, the surface finish may besurface finish may be considered satisfactory if it is produced within the
considered satisfactory if it is produced within the limits of sizelimits of size and form in accordance with ASME/ANSI Y14.5M-1994. and form in accordance with ASME/ANSI Y14.5M-1994. When surface texture symbology is used,
When surface texture symbology is used, it is consideredit is considered applicable to the finished surface of the
applicable to the finished surface of the object.object.
2.0
2.0 THE THE BASIC BASIC SYMBOLSYMBOL Use of the basic
Use of the basic surface texture symbol is indicated where thesurface texture symbol is indicated where the surface may be produced by any method. If the surface is to be surface may be produced by any method. If the surface is to be produced to net form (where
produced to net form (where material removal is prohibited),material removal is prohibited), the circle symbol is added to the basic symbol. Examples of the circle symbol is added to the basic symbol. Examples of this principle include surfaces that may be produced by this principle include surfaces that may be produced by diedie casting, forging, hot finishing, cold finishing, sintering, casting, forging, hot finishing, cold finishing, sintering, injection molding, or other processes where no
injection molding, or other processes where no material needmaterial need be removed for acceptable surface finishes. See Figure be removed for acceptable surface finishes. See Figure 2.2.
Figure 1. ASME/ANSI Figure 1. ASME/ANSI Y14.36M-1995 Surface Y14.36M-1995 Surface Texture Symbol Size and Texture Symbol Size and Proportion
Proportion
Figure 2. Basic surface texture symbol and
Figure 2. Basic surface texture symbol and variations forvariations for 1) material removal prohibited, 2) material removal 1) material removal prohibited, 2) material removal allowed, and 3) material removal allowed to a
allowed, and 3) material removal allowed to a minimumminimum value
value
2
2
Basic symbol with Basic symbol with material removal material removal prohibited (net form) prohibited (net form)
Basic symbol with Basic symbol with material removal material removal required required
Basic symbol with Basic symbol with value of minimum value of minimum material removal required material removal required
Basic
Basic
Surface Texture
Surface Texture
Symbol
Symbol
00
00
00
00
1.6
1.6
Text Height (1X) Text Height (1X) 60 60°° 3X Text Height 3X Text Height Expands with Expands with text length text lengthNOTES
NOTES
1.5X Text 1.5X Text Height Height 3X Text Height 3X Text Height Minimum Minimum +1X for each added +1X for each added line of text over two line of text over twoL
Lay symbolN
R
a
L / R
z
Roughness cutoff or Sampling Length Roughness Average RaProduction methodology, treatment, other text, notes, callouts, etc.
Roughness Value Other than Ra
Table 1
Preferred Series Roughness Average Values, Ra Micrometers (
µ
m) Microinches (µ
in)0.012 (0.025) (0.05) 0.075 (0.1) 0.125 0.15 (0.2) 0.25 (0.32) (0.4) 0.5 0.63 (0.8) 1 1.25 (1.6) 2 2.5 (3.2) 4 5 (6.3) 8 10 (12.5) 15 20 (25)
( ) Recommended for normal use. 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.” 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 Raare 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 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 B46.1M-1995. 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. 5.0 APPLICATION OF VALUES AND UNITS
Only those values and specifications needed to verify the Figure 3. Parameters That May be Included in the Texture Symbol .5 (1) (2) 3 (4) 5 6 (8) 10 13 (16) 20 25 (32) 40 50 (63) 80 100 (125) 160 200 (250) 320 400 (500) 600 800 (1000)
Update 56
Surface Texture
February 1997*Table 2
Standard Sampling Length (Cutoff) Values
Millimeters Inches 0.08 0.25 0.8 2.5 8 25
Figure 4. Samples of Surface Texture Applications
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 gener-ally indicative of the direction that generates the maximum value, usually across the lay.
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-0.003 0.010 0.030 0.10 0.30 1.00
1.6 2.5
1.6 2.5
1.2
0.8 2.5
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.
Roughness Average with
upper and lower limits.
Units are micrometers.
Material removal is
allowed.
Material removal is not
allowed. Surface must be
produced to net
Roughness Average with
no secondary processing.
1.6 2.5
It is now mandatory that
the Roughness Sampling
Length or Cutoff rating be
explicitly stated.
0.8
1.6 2.5/Rz 0.8
Roughness
Sampling Length
or Cutoff for R
(2.5) when
diff-erent than
R (0.8).
0.8 / Rz 0.6-0.8
Roughness parameter other than R 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 S
Mis 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.
a
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,
Figure 5. Symbology for Special Processes and Operations
except where such information is essential to engineer-ing 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.
c
2.5 0.8 B WIDTH B 2.5 0.8 Ø8.1-8.2 Ø 14 12Example D
2.5 0.8 X Y X Y A B 2.5 0.8 A BExample C
MILL GRIND LAPExample A
Example B
Update 56
Surface Texture
February 1997*Note that per ASME/ANSI Y14.5M-1994, all dimensions and symbols are read from the bottom of the drawing and none are to
address hidden features. See Figure 8 for exception to bottom reading rule. Some dimensional information omitted for clarity.
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.
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 1 5 2 0 3 5 4 2 A B SIZE SYMBOL A B HOLEØ 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
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.
7.0 THE EXTENSION LEG
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.
Where surface texture symbols apply to parts involving plating or coating, notes or specifications should indicate if the surface texture value applies before plating, after plating, or both.
8.0 TERMINOLOGY RELATED TO SURFACE TEXTURE
8.1 Centerline is the graphical center between peaks and valleys when the area of the peaks and the area of the valleys is equal.
8.2 Cutoff is a value dictated by the response characteristics of the selected spacing limits of the roughness measuring instru-ment. As cutoff value is a function of the measurement instrument settings and not a measured value, it does not
require a tolerance. The chosen value should include all surface irregularities being ascertained.
8.3 Flaws are interruptions in the surface topology. They are unintentional, unwanted, and unexpected deviations from the nominal surface. Flaws often are included in roughness measurement.
8.4 Form, Error of, is considered to be a more substantial deviation from the nominal surface but is not included in surface texture.
8.5 Height is the inward or outward linear measurement which is perpendicular to the nominal surface.
8.6 Lay is the orientation of tool marks or surface patterns. It is dictated by the production processes employed.
8.7 Measured profile is the profile of the surface topography as produced and measured by instrumentation. Within
mea-surement capability, it is a faithful representation of the actual surface. 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 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 of solid material. It may include flaws and tool marks caused by the manufacturing processes used to produce the surface. Roughness may also include traverse feed marks within the sample width. See Figure 10.
8.12 Roughness Average is also known as arithmetic average (AA) and centerline average (CLA). It is the arithmetic average of the sum of the deviations, above and below the centerline of the sample width. Deviations are measured perpendicular to the centerline. The RMA (root mean average) technique is also used and will generate different results. See Figure 10. 8.13 Roughness sampling width is the sampling width chosen to measure roughness characteristics separately from characteristics designated as waviness. It is measured parallel to the nominal surface. See Figure 10.
8.14 Surface texture is the sum total of all irregularities caused by roughness, waviness, and flaws. It may be regular or random.
8.15 Traverse width is the sampling width the stylus of the measurement instrument travels in order to generate a represen-tative sample. It is measured parallel to the nominal surface. 8.16 Valley is a point of lowest depth below the centerline and between two peaks. It is measured perpendicular to the nominal surface. See Figure 10.
8.17 Waviness is the more widely spaced measure of the surface topology. Waviness usually includes all irregularities greater than the roughness sampling width but within the waviness sampling width. Waviness may be caused by process
Update 56
Surface Texture
February 1997*Figure 10. Surface Characteristics
Waviness
Width
Waviness
Height
Flaws
Lay
Typical Transvers
ing Width
Roughness
Average R
a
Valleys
Peaks
Roughness
Width
Roughness
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 re-moved. 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 irregulari-ties 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 0.025µm, with 1.6 to 0.10µm 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 pro-duced.
Update 56
Surface Texture
February 1997*Section A-A
C
Section A-A
R
Section A-A
P
X
Section A-A
M
X
M
C
R
P
Radial lay orientation relative to the
center of the surface displaying the
surface texture symbol.
Perpendicular orientation relative to the
surface in the view displaying the
surface texture symbol.
Angular lay orientation in both directions
relative to the surface in the view
displaying the surface texture symbol.
Multidirectional lay orientation relative to
the surface in the view displaying the
surface texture symbol.
Circular lay orientation relative to the
center of the surface displaying the
surface texture symbol.
Parallel lay orientation relative to the
surface in the view displaying the
surface texture symbol.
Particulate, non-directional, or
protuberant lay orientation relative to the
surface displaying the surface texture
symbol.
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
Ranges shown are typical. Higher or lower values may be obtained under special conditions. 50 2000 25 1000 12.5 500 6.3 250 3.2 125 1.6 63 0.80 32 0.40 16 0.20 8 0.10 4 0.05 2 0.025 1 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 3
ISO Surface Finish Designations and Differences from ANSI
Update 61 July 1999
by B. Harding*
1.0 TREATMENT OF SURFACE FINISH SYMBOLOGY ISO standards are published in a different fashion than A meri-can 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.
2.0 ISO STANDARDS
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:
• 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,
defini-tions 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 speci-mens, roughness comparison specispeci-mens, and establishes requirements for stylus-type instruments. As with American National Standard ASME Y14.36M, ISO 1302 is not con-cerned 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 abrad-ing, castabrad-ing, coatabrad-ing, cuttabrad-ing, etchabrad-ing, plastic deformation, sintering, wear, erosion, etc.
2.2 Units
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-of-roundness 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.
2.3 Appearance
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.
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 in-spected 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 µmust be from the upper limit. See Figure 4.
d
a
2
f
2
c / f
1
b
a
1
e
h
d '
x
x '
c / f
e
Roughness value in micrometers preceded by parameter symbold
Production method Machine allowance Surface patternRoughness value other than Ra (micrometers)
In future versions of 1302, all roughness values will be allowed at location 'a' only Waviness height preceded by parametric symbol or sampling length (millimeters)
a
b
Basic symbol for material removal pro-hibited and left in the state from a previous manufacturing process
Basic symbol for surface under consideration or to a specification explained elsewhere in a note
Basic symbol for a surface to be machined
Basic symbol with all round circle added
Text height h (ISO3098-1) 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
a
1a
2ISO Surface Finish Designations and Differences from ANSI
Update 61 July 1999
Figure 3. Examples of ISO Applications of Surface Texture Symbology
Interpretation
Example
Surface roughness is produced by milling and
between upper limit of Ra = 50
µ
m and Ra = 6.3
µ
m; direction of lay is crossed in oblique
direc-tions relative to plane of projection; sampling
length is 5 mm.
Surface roughness of Rz = 6.3
µ
m is the default
for all surfaces except the inside diameter which
is Ra = 0.8
µ
m.
Surface roughness is produced by grinding to
Ra = 1.2
µ
m and limited to Ry = 6.3 max;
direction of lay is perpendicular relative to the
plane of projection; sampling length is 2.5 mm.
Surface treatment without any machining;
nickel-chrome plated to Rz = 1
µ
m on all surfaces.
Surface is nickel-chrome plated to roughness of
Ra = 3.2
µ
m with a sampling length of 0.8 mm;
limited to Rz = 16
µ
m to Rz = 6.3
µ
m with a
sampling length of 2.5 mm.
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
projec-tion lines.
Ra 50
milled
Ra 6,3
5
X
Rz 6,3( )
Ra0,8 Ra 1,2 ground 2,4/Ry 6,3 MAXFe/Ni20pCrr
Rz 1
Fe/Ni10bCrr Ra 3,2 0,82,5/Rz 16 2,5/Rz 6,3 Ra0,8 R a 0 , 8 2x45˚ R a 1 , 6 R 3 R a 0 ,8 Rz 40 O 4 5 4 0 ˚Built-up surface Ground
Interpretation
Example
Figure 3. Examples of ISO Applications of Surface Texture Symbology - continued
Surface texture symbology and dimensions may
be combined on leader lines.
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.
Symbology can be used for dimensional
infor-mation and surface treatment.
Rz 40 3xO5 Ra1,6 R 3 Fe/Cr50 Ground Ry6,2 Ry1,6 30 O 4 5
ISO Surface Finish Designations and Differences from ANSI
Update 61 July 1999
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 ROUGH-NESS 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. TABLE 1
Current ISO Surface Texture Parameters
Figure 4. Roughness Parameter Value Curves Showing Mean and Standard Deviation
TABLE 3
Roughness Sampling Lengths for Rz, Rv, Rp, Rc, Rt, and Curves for Non-periodic Profiles Such as Ground Surfaces
TABLE 2
Roughness Sampling Lengths for Ra, Rq, Rsk, Rku, R∆∆∆∆∆q, and Curves for Non-periodic Profiles Such as Ground Surfaces Symbol
Parameter (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 Rδc Sampling length—primary profile lp Sampling length—waviness profile lw Sampling length—roughness profile lr
Evaluation length ln
Ordinate value Z(x)
Localslope dZ/dX
Profile peak height Zp Profile valley depth Zv Profile element height Zt Profile element width XL Material length of profile Ml
Roughness Roughness Ra Sampling Evaluation Length (lr) Length (ln) µm mm mm (0.006) < Ra≤0.02 0.08 0.4 0.02 < Ra≤0.1 0.25 1.25 0.1 < Ra≤2 0.8 4 2 < Ra≤10 2.5 12.5 10 < Ra≤80 8 40 Roughness Roughness Rz, Rz1max Sampling Evaluation Length (Ir) Length (In)
µm mm mm (0.025) < Rz, Rz1max≤0.1 0.08 04 0.1 < Rz, Rz1max≤0.5 0.25 1.25 0.5 < Rz, Rz1max≤10 08 4 10 < Rz, Rz1max≤50 2.5 125 50 < Rz, Rz1max≤200 8 40 1 2 1 2 Upper limit of surface texture parameter
TABLE 5
Preferred Roughness Values and Roughness Grades
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.
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
TABLE 4
Roughness Sampling Lengths for R-Parameters and RSm Curves for Periodic and Non-periodic Profiles
Roughness Roughness RSm Sampling Evaluation Length (lr) Length (ln) µm mm mm 0.013 < RSm≤0.04 0.08 04 0.04 < RSm≤013 0.25 1.25 0.13 < RSm≤0.4 08 4 0.4 < RSm≤1.3 25 12.5 1.3 < RSm≤4 8 40
Roughness Values Ra ISO Grade Number from previous µm µin version of ISO 1302 50 2000 N12 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.
5.1 Prior Practice
Prior to the adoption of current preferred roughness specifica-tion, 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.
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).
Sampling Length
