While smoothing the end of a steel bar on a workshop bench grinder, an operator begins pressing the workpiece firmly against the flat side of a standard straight (Type 1) vitrified abrasive wheel. Which of the following explains why grinding on the side of a standard straight abrasive wheel is dangerous and strictly prohibited?
- ASide grinding creates excessive electrical resistance that immediately trips the internal motor thermal breaker
- Standard straight abrasive wheels are engineered only for radial perimeter contact and can easily fracture under lateral side pressureAnswer
- CSide pressure causes the arbor nut to reverse thread and spin off the spindle shaft during operation
- DContact with the side of the wheel reverses the abrasive grain cutting action and dulls the motor bearings
Answer
Standard straight abrasive wheels are engineered only for radial perimeter contact and can easily fracture under lateral side pressure.
Standard straight (Type 1) grinding wheels are designed and bonded specifically to handle rotational cutting forces along their outer perimeter (circumference). They possess minimal lateral strength. Applying a workpiece against the flat side of a standard wheel introduces bending stresses that can crack the vitrified bond, resulting in the wheel shattering at high velocity and causing severe injury.
Step-by-Step Solution
Key Concept
Grinding Wheel Structural Limits and Side-Grinding Safety
Estimated Time:1m 0s