Abrasive Wheels Training Certificate Speed Calculations and Markings 2

Question 1

What information must be marked on every abrasive wheel according to BS EN 12413?

Accepted Answer

Manufacturer, maximum operating speed, wheel dimensions, abrasive type, bond type, and expiry date (for resinoid wheels)

Answer

BS EN 12413 requires the following markings: manufacturer's name/trademark, maximum operating speed (RPM and/or m/s), wheel dimensions (diameter × thickness × bore), abrasive type, grain size, grade, structure, bond type, and for resinoid wheels, the use-by date.

Question 2

What happens to the centrifugal force acting on an abrasive wheel if the RPM is doubled?

Accepted Answer

It quadruples (increases by a factor of 4)

Answer

Centrifugal force is proportional to the square of the rotational speed (F = mω²r). If the RPM is doubled, the centrifugal force increases by a factor of 2² = 4. This is why even a small increase in speed beyond the maximum rating can be extremely dangerous.

Question 3

Before fitting an abrasive wheel to a machine, what speed-related check must the operator perform?

Accepted Answer

Verify that the machine's spindle speed does not exceed the wheel's maximum rated RPM

Answer

The operator must verify that the machine's spindle speed (RPM) does not exceed the maximum RPM marked on the abrasive wheel. If the machine speed exceeds the wheel's rating, the wheel must not be fitted. This check is one of the most critical safety steps in wheel mounting.

Question 4

What is the speed colour code for an abrasive wheel rated at 80 m/s?

Accepted Answer

Red

Answer

The speed colour coding under BS EN 12413 is: 50 m/s = Blue, 63 m/s = Yellow, 80 m/s = Red, 100 m/s = Green. The red band on an 80 m/s wheel provides immediate visual identification of the speed rating.

Question 5

An angle grinder runs at 11,000 RPM. Which of the following disc diameters would be UNSAFE if the disc is rated at 80 m/s maximum peripheral speed?

Accepted Answer

180 mm

Answer

At 11,000 RPM, the peripheral speed for a 180 mm disc would be: (π × 180 × 11,000) / 60,000 = 103.7 m/s, which exceeds the 80 m/s maximum. For 125 mm: 72.0 m/s (safe). For 115 mm: 66.0 m/s (safe). For 100 mm: 57.6 m/s (safe). The 180 mm disc must not be used.

Abrasive Wheels Practice Test

Abrasive Wheels Practice Test

Abrasive Wheels Training Certificate Speed Calculations and Markings 2