Abrasive Wheels Training Certificate Abrasive Wheel Types and Selection 2

Question 1

Which grade of abrasive wheel should be selected for grinding hardened steel?

Accepted Answer

A soft grade wheel (A-H)

Answer

A soft grade wheel (A-H) should be used for grinding hard materials. Soft wheels release worn grains more easily, exposing fresh cutting edges. Hard wheels are used for soft materials. This is known as the 'reverse rule'.

Question 2

What is a Type 27 abrasive wheel commonly known as in the workplace?

Accepted Answer

A depressed centre grinding disc

Answer

Type 27 wheels are depressed centre grinding discs, commonly used on angle grinders. The depressed centre allows the wheel to grind flush against the workpiece without the spindle nut interfering.

Question 3

What is the main difference between an organic bond and a vitrified bond in abrasive wheels?

Accepted Answer

Organic bonds (resinoid/rubber) are more flexible and shock-resistant than vitrified bonds

Answer

Organic bonds (resinoid and rubber) are more flexible and shock-resistant, making them suitable for portable and hand-held grinding. Vitrified (ceramic) bonds are rigid and brittle but offer excellent heat resistance and are used for precision grinding.

Question 4

When selecting an abrasive wheel for use on an angle grinder, which specification must always match?

Accepted Answer

The bore size must match the grinder spindle diameter

Answer

The bore size (centre hole) of the wheel must exactly match the spindle diameter of the grinder. An incorrect bore size will cause the wheel to be off-centre, leading to dangerous vibration and potential wheel failure.

Question 5

What does an 'open' structure number (7-14) in an abrasive wheel marking indicate?

Accepted Answer

The wheel has fewer abrasive grains with more spacing between them

Answer

Structure numbers range from 0 (dense/closed) to 14 (open). Higher numbers indicate wider spacing between grains, which provides better chip clearance and is suited for softer, gummier materials that would otherwise clog the wheel.

Abrasive Wheels Practice Test

Abrasive Wheels Practice Test

Abrasive Wheels Training Certificate Abrasive Wheel Types and Selection 2