Abrasive Wheels Training Certificate Speed Calculations and Markings

Question 1

What does the maximum RPM marked on an abrasive wheel indicate?

Accepted Answer

The absolute maximum speed at which the wheel may be operated — exceeding it risks catastrophic failure

Answer

The recommended operating speed for best results

Answer

The speed at which the wheel was tested at the factory

Answer

The minimum speed required for effective cutting

Question 2

An abrasive wheel has a maximum speed of 80 m/s marked on it. What does this represent?

Accepted Answer

The maximum peripheral (surface) speed of the wheel

Answer

The speed the grinder moves across the floor

Answer

The speed of the sparks leaving the wheel

Answer

The feed rate of the workpiece

Question 3

If an abrasive wheel has a diameter of 300 mm and a maximum peripheral speed of 50 m/s, what is its maximum RPM?

Accepted Answer

3,183 RPM

Answer

1,592 RPM

Answer

4,775 RPM

Answer

6,366 RPM

Question 4

Why does the maximum safe RPM of an abrasive wheel increase as the wheel wears and its diameter decreases?

Accepted Answer

Because centrifugal force at the rim decreases with smaller diameter at the same RPM, so the wheel can safely spin faster while staying within its maximum peripheral speed

Answer

Because a smaller wheel is lighter

Answer

Because worn wheels are stronger

Answer

The maximum RPM does not change as the wheel wears

Question 5

What colour is the standard speed marking band on an abrasive wheel rated for a maximum speed of 50 m/s?

Accepted Answer

Blue

Answer

Red

Answer

Green

Answer

Yellow

Question 6

A bench grinder has a spindle speed of 2,850 RPM. What is the maximum diameter wheel that can be used if the wheel's maximum peripheral speed is 33 m/s?

Accepted Answer

221 mm

Answer

150 mm

Answer

200 mm

Answer

300 mm