Question

A grinding wheel is specified by ``C24K7V'' for finish grinding of a tool. The first letter ``C'' is represented by

• A. Type of bond, Vitrified
• B. Type of bond, Silicate
• C. Type of abrasive, Cubic Boron Nitride
• D. Type of abrasive, Silicon Carbide

Hint:

In grinding wheel specs (e.g., C24K7V), the first letter denotes the abrasive (C = Silicon Carbide, A = Aluminum Oxide, B = CBN), and the last letter denotes the bond (V = Vitrified).

Answer 1

The Correct Option is D

Step 1: Understand grinding wheel specification.
A grinding wheel specification (e.g., C24K7V) follows a standard marking system that indicates its characteristics:
First letter: Type of abrasive,
Second number: Grain size (coarse to fine),
Third letter: Grade (hardness of the wheel, A to Z, soft to hard),
Fourth number: Structure (density of abrasive grains, 1 to 15, dense to open),
Last letter: Type of bond.
Step 2: Interpret the given specification ``C24K7V''.
The first letter ``C'' indicates the type of abrasive.
Common abrasives include:
A: Aluminum Oxide (used for steels),
C: Silicon Carbide (used for cast iron, non-ferrous metals, and non-metallic materials),
B: Cubic Boron Nitride (CBN, used for hard materials like tool steels), D: Diamond (used for very hard materials like ceramics).
The last letter ``V'' indicates the bond type, which is Vitrified (a common ceramic bond).
The wheel is used for finish grinding of a tool, which often involves hard materials like tool steel, but the abrasive type must match the first letter.
Step 3: Determine the meaning of ``C''.
``C'' in grinding wheel specifications stands for Silicon Carbide, not Cubic Boron Nitride (which is denoted by ``B'').
Silicon Carbide is often used for grinding non-ferrous metals, cast iron, or in some cases for finishing tools, especially if the tool material is compatible (e.g., carbide tools).
Step 4: Evaluate the options.
(1) Type of bond, Vitrified: Incorrect, as ``Vitrified'' is represented by the last letter ``V'', not the first letter ``C''. Incorrect.
(2) Type of bond, Silicate: Incorrect, as ``Silicate'' bond is represented by ``S'', not ``C''. Incorrect.
(3) Type of abrasive, Cubic Boron Nitride: Incorrect, as Cubic Boron Nitride is denoted by ``B'', not ``C''. Incorrect.
(4) Type of abrasive, Silicon Carbide: Correct, as ``C'' stands for Silicon Carbide in grinding wheel specifications. Correct.
Step 5: Select the correct answer.
The first letter ``C'' in the grinding wheel specification represents the type of abrasive, Silicon Carbide, matching option (4).