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Questions and Answers
What is the primary purpose of superfinishing?
What is the primary purpose of superfinishing?
Which grain size is typically used for superfinishing abrasive sticks?
Which grain size is typically used for superfinishing abrasive sticks?
How does superfinishing differ from honing in terms of stroke length?
How does superfinishing differ from honing in terms of stroke length?
What type of machine tools are often used for the superfinishing process?
What type of machine tools are often used for the superfinishing process?
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What is the role of pressure in the superfinishing process compared to honing?
What is the role of pressure in the superfinishing process compared to honing?
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Which of the following terms is associated with surface quality improvement in the superfinishing process?
Which of the following terms is associated with surface quality improvement in the superfinishing process?
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What motion is applied to the abrasive stick during superfinishing?
What motion is applied to the abrasive stick during superfinishing?
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In superfinishing, what is the effect of using very fine grit materials?
In superfinishing, what is the effect of using very fine grit materials?
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What is the grit number range typically associated with honing processes?
What is the grit number range typically associated with honing processes?
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What characteristic surface finish does the honing process create?
What characteristic surface finish does the honing process create?
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How much material is typically removed during a superfinishing operation?
How much material is typically removed during a superfinishing operation?
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Which of the following materials can be subjected to superfinishing?
Which of the following materials can be subjected to superfinishing?
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What advantage does the floating mechanism in honing provide?
What advantage does the floating mechanism in honing provide?
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Which type of surface quality is desired from superfinishing operations?
Which type of surface quality is desired from superfinishing operations?
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What is the primary function of bonding agents in superfinishing?
What is the primary function of bonding agents in superfinishing?
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Which of the following statements about honing tools is false?
Which of the following statements about honing tools is false?
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Which machining process is primarily used for achieving a roughness average (Ra) as fine as 0.1 microns?
Which machining process is primarily used for achieving a roughness average (Ra) as fine as 0.1 microns?
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What is the main advantage of honing compared to other surface finishing processes?
What is the main advantage of honing compared to other surface finishing processes?
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Which of the following abrasive materials is commonly used in superfinishing operations?
Which of the following abrasive materials is commonly used in superfinishing operations?
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Which machining tool comparison would typically show the least surface roughness after processing?
Which machining tool comparison would typically show the least surface roughness after processing?
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What is the typical range of roughness average (Ra) for grinding operations?
What is the typical range of roughness average (Ra) for grinding operations?
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Which of the following processes typically results in improved surface quality through a process of removal of small amounts of material?
Which of the following processes typically results in improved surface quality through a process of removal of small amounts of material?
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Which parameter primarily indicates the quality of a surface and is often used to characterize it?
Which parameter primarily indicates the quality of a surface and is often used to characterize it?
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Which abrasive machining process is best suited for refining surfaces to a low roughness value?
Which abrasive machining process is best suited for refining surfaces to a low roughness value?
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Study Notes
Abrasive Machining
- Abrasive machining processes remove material using abrasive particles.
- Nearly all surfaces have peaks and valleys.
- The difference in height between the peaks and valleys is usually about one micrometer.
- A good surface finish has smaller peaks and valleys.
- Surface finish is characterized by parameters like roughness average, root mean square roughness, maximum peak-to-valley height, etc.
- Different machining processes result in different roughness parameters.
- Grinding, honing, and lapping are surface finishing processes.
Abrasive Machining Processes
- Grinding
- Honing
- Lapping
- Buffing/Polishing
- Abrasive jet machining
- De-burring (shot blasting, vibratory, and barrel finishing)
Grinding
- Grinding removes metal by abrasive particles (irregular shape).
- The abrasive grains use a zero to negative rake angle, creating short, small, curved, or wavy chips.
Types of Grinding
-
Purpose-based:
- Non-precision grinding: Primarily removes material, accuracy and finish are secondary concerns.
- Precision grinding: Focuses on achieving good surface finishes and precise dimensions.
-
Process/Procedure-based:
- Surface grinding (flat surfaces)
- Cylindrical grinding (cylindrical surfaces, may be centered or centerless)
- Form grinding (gears, threads etc.)
- Abrasive belt grinding (flats, curves, or cylinders)
- Manual grinding (workpiece or grinder held by hand)
- Special grinding processes (cam/crank shafts, gear grinders)
Grinding Machines
- Surface grinders
- Cylindrical grinders
- Centerless grinders
- Internal grinders
- Special types of grinders
Classification
- Based on purpose (non-precision, precision)
- Based on process/procedure (surface, cylindrical, form, belt, manual, special)
Centerless Grinding
- Eliminates the need for center holes in the workpiece.
- The workpiece rests on a workrest blade and is backed up by a regulating wheel.
- The regulating wheel rotates in the same direction as the grinding wheel and controls the workpiece feed.
Internal Grinding
- Used to finish straight, tapered, or formed holes in workpieces.
- The workpiece is held by a chuck or collet and revolved by a motorized headstock.
- The grinding wheel is fed in and out, adjusted for depth of cut.
Special Grinding Processes
- Tool and cutter grinders: Sharpen milling cutters, reamers, taps, etc.
- Jig grinders: Precisely grind tapered or straight holes.
- Thread grinding machines: Produce precise threads.
- Crankshaft grinders
- Piston grinders
- Cam grinders
- Tool-post grinders (lathe grinders)
Machining Parameters
- Cutting speed (V): Calculated using wheel diameter and rotational speed.
- Metal removal rate (Z): Calculated using depth of cut, cross feed, and table speed.
- Machining time (tm): Calculated using thickness, width of work piece, cross feed, depth of cut etc.
Abrasives
- Natural abrasives (e.g., sandstone, quartz, emery, corundum, diamond)
- Manufactured abrasives (e.g., aluminum oxide, silicon carbide, cubic boron nitride, diamond)
- Grain sizes range from 10 (very coarse) to 600 (very fine)
- Grit number relates to sieve mesh size.
Bonding Materials
- Vitrified
- Silicate
- Shellac
- Resinoid
- Rubber
- Metal bonds
- Electroplated bond
- Brazed bond
Grades of Hardness
- Grinding wheel hardness, measured using a letter system (softest 'A', hardest 'Z').
- Hardness considerations should match the grain size.
Glazing and Loading
- Glazing: Wheel face becomes smooth, cutting ability decreases.
- Loading: Metal particles adhere to the wheel face, reducing cutting ability.
Dressing and Truing
- Dressing: Cleaning and restoring the grinding wheel's cutting surface.
- Truing: Ensuring the cutting surface is smooth and true, crucial for precision grinding.
Grinding Ratio (G)
- G = Volume of material removed / Volume of wheel wear
- Varies depending on the type of wheel, grinding fluid, and process parameters.
- Higher forces typically reduce the grinding ratio.
Abrasives - Workpiece Material Compatibility
- The reactivity between abrasives and workpieces influences wear.
- Certain combinations are commonly used based on material compatibility.
Mechanics of Grinding
- Chips form due to the negative rake angle of the abrasive grains.
Application Guidelines
- Consider factors like grit size, wheel structure, wheel speeds, work speed, depth of cut, wheel diameter, bond type, to select right wheel for application.
Lapping
- Final finishing operation for extreme dimensional accuracy, correcting imperfections, refining surface finish, and achieving close fits between surfaces.
- Uses loose abrasives like emery, corundum, iron oxide.
- Materials lapped range from optical lenses to precision plug gages.
Honing
- Abrasive process with low velocity.
- Primarily used for correcting internal cylindrical surfaces, tool marks, taper, and axial distortion
- Produces a cross-hatched surface.
Superfinishing
- Extremely high-quality surface finish process.
- Minimizes defects and removes a very thin layer of metal.
- Used for external and internal surfaces of parts.
- Uses fine grit abrasive sticks and spring pressure.
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Description
Test your knowledge about abrasive machining processes and their characteristics. This quiz covers various surface finishing techniques such as grinding, honing, and lapping, along with their parameters and applications. Discover how these processes impact surface quality and production efficiency.
