Podcast
Questions and Answers
What does the symbol 'Ra' represent in surface texture indication?
What does the symbol 'Ra' represent in surface texture indication?
Which of the following is NOT a current method for indicating surface roughness in engineering drawings?
Which of the following is NOT a current method for indicating surface roughness in engineering drawings?
What does the addition of a bar to the basic surface roughness symbol indicate?
What does the addition of a bar to the basic surface roughness symbol indicate?
The worldwide conventions for indicating surface roughness include how many methods?
The worldwide conventions for indicating surface roughness include how many methods?
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What shape is formed by the basic symbol used to indicate surface texture?
What shape is formed by the basic symbol used to indicate surface texture?
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Where can surface texture requirements be indicated to avoid misinterpretation?
Where can surface texture requirements be indicated to avoid misinterpretation?
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What is required when different surface textures are needed for individual prismatic surfaces?
What is required when different surface textures are needed for individual prismatic surfaces?
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If surface texture must be defined both before and after treatment, how should this be communicated?
If surface texture must be defined both before and after treatment, how should this be communicated?
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Where is it permissible to place the surface texture requirement in relation to geometrical tolerances?
Where is it permissible to place the surface texture requirement in relation to geometrical tolerances?
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What is a requirement for indicating surface texture on cylindrical features?
What is a requirement for indicating surface texture on cylindrical features?
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What is required when there are special surface characteristics to indicate?
What is required when there are special surface characteristics to indicate?
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How should maximum and minimum limits of the principal criterion of surface roughness be represented?
How should maximum and minimum limits of the principal criterion of surface roughness be represented?
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What is implied when a circle is added to the complete graphical symbol?
What is implied when a circle is added to the complete graphical symbol?
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Where should surface texture requirements typically be indicated on technical drawings?
Where should surface texture requirements typically be indicated on technical drawings?
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What does the orientation of the graphical symbol and its annotation need to comply with?
What does the orientation of the graphical symbol and its annotation need to comply with?
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How should the graphical symbol connect to the surface it refers to?
How should the graphical symbol connect to the surface it refers to?
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What happens if one particular production method is required for the surface texture?
What happens if one particular production method is required for the surface texture?
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What characterizes the presentation of surface texture requirements on technical documentation?
What characterizes the presentation of surface texture requirements on technical documentation?
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Study Notes
Surface Texture
- Surface texture encompasses roughness, waviness, lay, and flow
- Manufacturing processes and part structures affect surface characteristics
- Multiple methods exist for interpreting surface roughness plots
- Common methods include:
- Distance between peak to centerline
- Average distance between peaks and valleys for sample length
- Sum of average of first 5 peaks and valleys
- Maximum peak to valley height
- Maximum peak height
- RMS of peak and valley average
- Variations in surface roughness methods exist worldwide, exceeding 128 conventions
- Common method is interpreting average roughness (Ra), where R stands for roughness and a for average.
- Other methods include Rz, Rt, and Rmax
- Ra (Roughness Average) is the most common indicator of surface roughness and is indicated on technical drawings
- Surface roughness is now indicated using symbols, superseded the older triangle symbols, though some companies may still use triangle symbols
- A table correlates Ra values with roughness grades and corresponding symbols
- Basic symbol for surface texture involves two unequal length lines angled approximately 60 degrees relative to the line representing the surface
- Thin lines are used for the symbol
- If machining removes material, an additional bar is added
- If material removal is not allowed, a circle is added
- Special surface characteristics can be illustrated using additional lines on the symbols
- Numerical values defining roughness criteria are added to the symbols, including maximum and minimum limits
- Production method(s) can be noted on an extension line or other extensions of the symbol
- Unique methods are indicated when needed
- Surface texture values are typically specified once per surface, ideally on the same view as size and location of the surface
- Symbols are oriented for readability (bottom/right side of the drawing)
- Surface texture requirements can be indicated on dimension lines or tolerance frames; this applies when no risk of misunderstanding is present
Symbols of Lay
- Parallel: Symbol is parallel to projection plane of drawing view
- Perpendicular: Symbol is perpendicular to projection plane of drawing view
- Crossed: Symbol is crossed in two slant directions relative to projection plane of view
- Multidirectional: No specific direction, multidirectional
- Circular: Approximately circular relative to centre of surface
- Radial: Approximately radial relative to surface centre
Graphical Symbol for "All Surfaces Around a Workpiece Outline"
- A circle is added to the complete graphical symbol if all surfaces have the same texture around a work piece outline.
- The outline represents all surfaces
- Texture requirements are shown once per surface, in the location where the size or position of the surface is shown
- Texture specifications are indicated on the same view to minimize confusion
Positioning and Orientation of Graphical Symbols
- Symbols and supplementary information should be on the bottom or right side of the drawing
- Texture requirements are connected to surfaces using reference lines and arrowheads, or placed on extension lines
- Reference lines point to the relevant surface
On Dimension Line/Feature-of-Size Dimensions
- Surface texture requirements can be noted on dimension lines when no risks of misinterpretation are present
Tolerance Frame for Geometrical Tolerances
- Surface texture requirements may be noted on tolerance frames
Cylindrical and Prismatic Surfaces
- On a cylindrical surface, surface texture info may be placed once on a centerline if all indicated surfaces have the same texture info
- Distinct texture info is needed on each prismatic surface if there are different textures, as shown in the provided figures
- All prismatic surfaces must have texture info specified uniquely
Indication of Two or More Manufacturing Methods
- Separate note or Figure is included if two or more surface texture specifications are needed (i.e., before and after treatment)
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Description
This quiz delves into the various aspects of surface texture, including roughness, waviness, and the different methods used to interpret surface roughness plots. Explore the common metrics such as Ra, Rz, and others, as well as the impact of manufacturing processes on surface characteristics. Test your knowledge on modern conventions and symbols for indicating surface roughness in technical drawings.