Abrasive Wheels Training Certificate Abrasive Wheel Types & Grades 2 — Questions and Answers
Question 1: What type of abrasive wheel is a 'cut-off wheel' (parting wheel) designed for?
- Cutting through materials in a straight line; it has a thin profile and should not be used for side grinding (Correct answer)
- Grinding curved surfaces on lathes
- Dressing other grinding wheels
- Polishing workpiece surfaces to a mirror finish
Correct answer: Cutting through materials in a straight line; it has a thin profile and should not be used for side grinding
Cut-off (parting) wheels are thin-profile wheels designed solely for cutting through material. Their thin cross-section makes them structurally unsuitable for lateral forces. Using a cut-off wheel for side grinding will cause flexing, possible cracking, and potentially catastrophic burst. They should only be used for straight cutting.
Question 2: What is a 'flap disc' and how does it differ from a conventional grinding wheel?
- A disc made of overlapping abrasive flaps; it is more flexible than a rigid grinding wheel and provides a better surface finish (Correct answer)
- A disc used only for cutting operations
- A type of wire brush used for rust removal
- A disc used only on non-ferrous metals
Correct answer: A disc made of overlapping abrasive flaps; it is more flexible than a rigid grinding wheel and provides a better surface finish
Flap discs consist of overlapping strips (flaps) of abrasive cloth or paper bonded to a backing plate. They are more flexible than rigid grinding wheels, conform better to curved surfaces, and produce a finer finish. They are used for blending, finishing, and light stock removal on angle grinders.
Question 3: Diamond cutting wheels are different from conventional abrasive wheels in which key respect?
- Diamond grains are embedded in the wheel bond and do not break down during cutting; the wheel cuts by abrasion with extremely hard industrial diamond (Correct answer)
- Diamond wheels are made from natural gemstone diamonds
- Diamond wheels are used only for woodcutting
- Diamond wheels can be used at any speed without risk of overspeed
Correct answer: Diamond grains are embedded in the wheel bond and do not break down during cutting; the wheel cuts by abrasion with extremely hard industrial diamond
Industrial diamond wheels use synthetic diamond particles, the hardest known material, bonded to a steel or aluminium substrate. Unlike conventional abrasive wheels where grains break down, diamond grains endure. Diamond wheels are used to cut extremely hard materials: concrete, masonry, glass, and ceramics.
Question 4: What does the 'specification code' printed on an abrasive wheel tell the user?
- The abrasive type, grain size, grade (hardness), structure, and bond type in a standardised sequence (Correct answer)
- Only the maximum operating speed
- Only the wheel diameter and bore size
- The name of the manufacturer and date of production
Correct answer: The abrasive type, grain size, grade (hardness), structure, and bond type in a standardised sequence
The standard specification code (e.g., A 36 L 5 V) reads: A = aluminium oxide abrasive, 36 = grain size, L = grade/hardness, 5 = structure, V = vitrified bond. This sequence (ANSI/ISO standard) allows the user to identify exactly what the wheel is made of and select the correct wheel for the application.
Question 5: Why must the bore size of an abrasive wheel match the spindle exactly?
- A loose bore allows the wheel to run off-centre, creating imbalance, vibration, and the risk of the wheel cracking or bursting (Correct answer)
- A loose bore simply reduces cutting efficiency
- The bore only matters for large wheels above 200mm diameter
- Bore mismatch only affects the wheel dressing procedure
Correct answer: A loose bore allows the wheel to run off-centre, creating imbalance, vibration, and the risk of the wheel cracking or bursting
The bore must be a proper fit on the spindle — neither loose nor requiring force to fit. A loose bore allows eccentric rotation, creating dynamic imbalance and vibration that can propagate cracks and lead to wheel burst. Reducing bushes can be used to adapt bore size but must be the correct type for the wheel.
Question 6: What is the difference between a 'straight wheel' (Type 1) and a 'recessed wheel' (Type 5) for bench grinders?
- A straight wheel has flat sides; a recessed (cup or saucer) wheel has one or both sides depressed to allow clearance for mounting flanges (Correct answer)
- Type 1 is for ferrous metals only; Type 5 is for non-ferrous metals
- A recessed wheel operates at higher speeds than a straight wheel
- Type 5 wheels require no ring test; Type 1 wheels always do
Correct answer: A straight wheel has flat sides; a recessed (cup or saucer) wheel has one or both sides depressed to allow clearance for mounting flanges
Wheel type describes shape. A Type 1 straight wheel has flat sides. Type 5 has a single recess; Type 7 has a double recess. Recessed wheels are used where the mounting flanges would otherwise interfere with the work. The recesses provide clearance without reducing the grinding face.
Abrasive Wheels Training Certificate Abrasive Wheel Types & Grades 2
What type of abrasive wheel is a 'cut-off wheel' (parting wheel) designed for?