1. Surface finish
Flóra Hajdu
B406

2. Content Surface finish characteristics Surface finish symbol
Surface finish on technical drawings
Simplifications
Technical drawing examples
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3. Surface finish
Modern development of high-speed machines has resulted in higher loadings and increased speeds of moving parts
To withstand these operation conditions with minimum friction and wear a particular surface finish is often essential
Specify the right surface to give aximum performance and service life at lowest cost
Factors that influence the choice on surface finish
Size and function of the parts
Type of loading
Speed and direction of movement
Operating conditions
Physical characteristics of both materials on contact
Type and amount of lubricant and contaminant
Temperature
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4. Surface finish
Modern development of high-speed machines has resulted in higher loadings and increased speeds of moving parts
To withstand these operation conditions with minimum friction and wear a particular surface finish is often essential
Specify the right surface to give aximum performance and service life at lowest cost
Factors that influence the choice on surface finish
Size and function of the parts
Type of loading
Speed and direction of movement
Operating conditions
Physical characteristics of both materials on contact
Type and amount of lubricant and contaminant
Temperature
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5. Surface finish Surface finish control To reduce friction
To control wear
Whenever a film or lubricant must be maintained between 2 moving parts (e.g. bearings, piston pins, helical and worm gears) the surface irregularities must be small enough so that they will not penetrate the oil film under the most severe operating conditions
Also important to the wear of certain pieces that are subject to dry friction (machine tool bits, clutch plates, brake drums)
Smooth finishes are essential on certain high-precision pieces (e.g. injectors, high-pressure cylinders)
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6. Surface finish characteristics
Roughness: consists of the finer irregularities in the surface texture, usually including those that result from the inherent action of the production process. These include traverse feed marks and other irregularities within the limits of the roughness-width cutoff
Roughness-Height Value: rated as the arithmetic average deviation expressed in micrometers measured normal to the center line.
Roughness spacing: the distance parallel to the nominal surface between the surccessive peaks or ridges that constitute the predominant pattern of the roughness
Roughness-Width Cutoff: The greatest spacing of repetitive surface irregularities is included in the measurement of averae roughness height
Waviness: usually the most widely spaced of the surface texture components and normally is wider than the roughness-width cutoff. Waviness may result from such factors as machine or work deflections, vibration, chatter, heat treatment or warping strains. Roughness may be considered as superimposed on a wavy surface. Waviness is not currently in ISO standards, it is included as part of the surface texture symbol to reflect present industrial practices in the USA
Lay: the direction of the predominant surface pattern, ordinaly determined by the production method used
Flaws: irregularities that occur at one place or at relatively infrequent or widely varying intervals in a surface, such as defects as cracks, blow holes, checks, ridges and scratches. Unless otherwise specified the effect of flaws is not included in the roughness height measurements
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7. Surface finish characteristics
Roughness: consists of the finer irregularities in the surface texture, usually including those that result from the inherent action of the production process. These include traverse feed marks and other irregularities within the limits of the roughness-width cutoff
Roughness-Height Value: rated as the arithmetic average deviation expressed in micrometers measured normal to the center line.
Roughness spacing: the distance parallel to the nominal surface between the surccessive peaks or ridges that constitute the predominant pattern of the roughness
Roughness-Width Cutoff: The greatest spacing of repetitive surface irregularities is included in the measurement of averae roughness height
Waviness: usually the most widely spaced of the surface texture components and normally is wider than the roughness-width cutoff. Waviness may result from such factors as machine or work deflections, vibration, chatter, heat treatment or warping strains. Roughness may be considered as superimposed on a wavy surface. Waviness is not currently in ISO standards, it is included as part of the surface texture symbol to reflect present industrial practices in the USA
Lay: the direction of the predominant surface pattern, ordinaly determined by the production method used
Flaws: irregularities that occur at one place or at relatively infrequent or widely varying intervals in a surface, such as defects as cracks, blow holes, checks, ridges and scratches. Unless otherwise specified the effect of flaws is not included in the roughness height measurements
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8. Surface finish characteristics
Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design
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9. Roughness values (Average) Roughness height value
Peak-to-valley roughness height
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10. Average roughness height value
𝑅𝑎= 1 𝑙 0 𝑙 𝑦 𝑑𝑥≈ 1 𝑛 1=1 𝑛 𝑦 𝑖
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11. Roughness height (peak and valley)
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12. Surface roughness range for common production
Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design
scan
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13. Surface roughness range for common production
scan
Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design
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14. Surface roughness range for common production
scan
Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design
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15. Roughness height ratings
Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design
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16. Roughness and tolerance
scan
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17. Surface finish symbol All surface finish should be given scan
A: optional material removal
B: obligatory material removal
C: no material removal
Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design
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18. Surface finish symbol A: roughness value in m
A-B:specifying minimum and maximum roughness
C:manufacturing process, surface treatment
D: lay symbol
E: machining allowance
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19. Lay symbols
scan
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20. Surface finish on technical drawings
The point of the symbol should be located
on the line indicating the surface
On an extension line from the surface
On a leader pointing to the surface or extension line
In case of small dimensions it can be placed on the dimension line if it is not ambiguous
The symbol applies to the entire surface unless otherwise specified
The symbol for the same surface should not be duplicated on other views
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21. Surface finish on technical drawings
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22. Surface finish on technical drawings
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23. Surface finish on technical drawings
The surface finish symbols cannot be crossed with other lines, other lines should be broken
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24. Surface finish on technical drawings
In case of symmetrical parts it is suifficient to give the surface finish only one surface
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25. Surface finish on technical drawings
In case of surfaces that will be machined together the roughness of all surfaces should be given. Simplification is allowed
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26. Surface finish on technical drawings
In case of surfaces that have the same dimension, but different surface finish the surfaces should be separated with a thin line and the surface finish should be given for both parts
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27. Surface finish on technical drawings
On assemlby drawings the surface finish of the assembled surfaces should be given, even if they are the same
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28. Surface finish on technical drawings - simplifications
Surface finish should not be given on surfaces, if a standard is given on the surface
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29. Surface finish on technical drawings - simplifications
If all the surfaces of a part have the same surface finish the surface finish should be placed above the title block
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30. Surface finish on technical drawings - simplifications
Most common surface finish can be given above the title block
If there is other surface finish an empty surface finish symbol in brackets should be placed next to it
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31. Surface finish on technical drawings - simplifications
On assembly drawings the dost common surface finish should be given after the item number
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32. Surface finish on technical drawings - simplifications
The surface finish of connecting surfaces
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33. Surface finish on technical drawings - simplifications
Surface finish that is repeated several times can be given identified
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34. Surface finish on technical drawings - simplifications
Surface finish that is repeated several times can be given identified
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35. Summary Surface finish Surface finish symbol
Surface finish on technical drawings
Simplifications

36. Thank You for Your attention!