Abrasive Wheel Types & Grades Flashcards
6 cards from real Abrasive Wheels Training Certificate practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Abrasive Wheel Types & Grades flashcards as text
What is the maximum peripheral speed (surface speed) typically specified for vitrified bench grinding wheels?
Answer: 33 m/s (approximately 6,600 RPM for a 150mm wheel) unless otherwise specified on the wheel
Vitrified grinding wheels for bench grinders are typically rated at a maximum surface speed of 33 m/s. Resinoid wheels for angle grinders may be rated up to 80 m/s. The maximum speed is marked on the wheel and must not be exceeded. RPM limits depend on wheel diameter — a larger wheel reaches the speed limit at a lower RPM.
Which abrasive is used for grinding cemented carbide (tungsten carbide) tooling?
Answer: Green silicon carbide (GC)
Green silicon carbide (GC grade) is the standard abrasive for grinding cemented carbide. Its extreme hardness (9.5 on Mohs scale) and sharp friable grains effectively grind the hard carbide matrix without excessive heat build-up. Aluminium oxide is too soft for carbide and causes rapid glazing.
What are 'depressed centre' wheels (Type 27) designed for on angle grinders?
Answer: Grinding and blending on flat surfaces where the raised centre allows the disc to sit at a shallow angle to the work
Type 27 depressed centre grinding discs have a raised hub that positions the working face at an angle to the workpiece when the tool is held at the typical angle grinder working angle. This geometry allows efficient grinding and blending on flat or curved surfaces while keeping the angle grinder body clear of the work.
What is 'cubic boron nitride' (CBN) and in which application is it typically used as an abrasive?
Answer: The second hardest material after diamond; used for precision grinding of hard steels and super alloys where diamond cannot be used due to chemical reactivity with iron
CBN (cubic boron nitride) is the second hardest material known, exceeded only by diamond. Unlike diamond, CBN does not react chemically with ferrous metals at grinding temperatures, making it ideal for precision grinding of hardened steels, high-speed steels, and aerospace super alloys where extreme dimensional accuracy and surface finish are required.
What is the significance of the 'maximum RPM' marking on an abrasive wheel?
Answer: It is the absolute upper speed limit at which the wheel may be safely operated; exceeding it risks wheel burst
The maximum RPM is a safety-critical marking — it defines the speed above which centrifugal forces may exceed the wheel's tensile strength and cause it to burst. The machine spindle speed must be verified to be at or below the maximum marked speed before the wheel is mounted. This is a legal requirement under PUWER.
What abrasive wheel type is a 'fibre disc' (resin fibre disc) and what is it used for?
Answer: A flexible disc with abrasive grain on a vulcanised fibre backing; used for aggressive stock removal, rust removal, and weld blending on angle grinders
Resin fibre discs have a vulcanised fibre (rigid but flexible) backing with abrasive grain resin-bonded to one side. Used with a backing pad on angle grinders, they provide aggressive material removal, weld blending, and rust removal. They are available in various grits from coarse to fine.