Bench grinder wheel buying guide

If you frequently use sharp tools, picking the right bench grinder and grinding wheels for your needs is absolutely essential. But a bench grinder is also the ultimate aid for a wide range of grinding tasks.

Most bench grinders come fitted with standard wheels which won't always be suitable for the types of tasks you want to perform. In fact, if you fall into the usual trap of assuming a basic wheel will do the job, you might just come to regret your purchase or even end up ruining your tools!

That's why it is imperative to match the material and quality of the grinding wheel to the materials or tools you want to grind, dress or sharpen.

What is a bench grinder wheel?

In the past, a rotating grinding machine would be equipped with blocks of sandstone. These machines were turned by hand and water would be used as a coolant. These days, efficiency is key meaning grinding wheels are manufactured industrially. Millions of abrasive grains are pressed together with a bond and adhered to a backing material.

Fitted to bench grinders and used at high speeds, these wheels can be used to shape, sharpen and deburr metal parts upon contact. The friction produced by this process causes materials to heat up and create sparks.

By choosing the correct grinding wheel quality and grain, you will ensure the bench grinder can do its job effectively. However, wear is normal and it's important to keep an eye on the profile of the grinding wheel to make sure it is in an acceptable condition.

Dressing your bench grinder regularly helps it to maintain an effective grit with an even cutting surface. A grinding wheel will be perfectly flat and even when new. If over time you notice it is becoming significantly unbalanced or is producing vibrations it is best to replace the wheel entirely.

Bench grinders often come equipped with wheels made with vitrified bonds with a maximum operating speed of 25 to 33 m/s.

The quality of grinding wheels is governed by the standard DIN 69100 which regulates bonded abrasive products according to the following criteria:

• material;

• grit;

• hardness;

• structure;

• bond.

There are two main types of abrasive materials:

• natural abrasives such as emery, silex, crushed glass and garnet;

• synthetic abrasives such as aluminium oxide, silicon carbide, zirconium and alumina.

These materials are all categorised depending on grit type which is often measured in microns (µ):

• fine grit - 20 to 63 µ

• medium grit - 63 to 160 µ

• coarse grit - 160 to 250 µ

Bench grinder wheel grit categories

All bench grinders come marked with the following product information.

Decoding the wheel marking system

• Shape: type 1 for flat.

• Size: outer diameter, thickness and hole size in mm.

• Specifications:

1. A: aluminium oxide-type abrasive such as Corindon or Alundun.

2. C: silicon carbide-type abrasive such as Crystolon or Carborundum.

3. D: diamond powder abrasive.

4. 60: grit type ranges from 6 to 600 and corresponds to number of openings in one square inch of a screen which a grain can pass through.

5. P: hardness grade that ranges from D to Z.

Structure indicates the space between the grains and ranges from 1 to 12.

• V: bond type.

• V: refers to a vitrified grinding wheel; B – resinoid (synthetic) bond; S for sodium silicate; R for rubber; E for shellac; M for metal bond used for diamond wheels.

Mohs scale

Mineral hardness is measured on a scale called the Mohs scale which ranges from 1 to 10 and categorises materials on a scale of very soft to very hard. For example talc is rated 1, salt is rated 2.5 and diamond is rated 10.

When ordering a wheel for your grinder you must respect the criteria listed above.

• Adapters and reduction bushes can be used to fit grinding wheels. But be careful – do not attempt to fit a larger grinding wheel than your bench grinder allows.

• Wear full safety goggles to prevent any debris from getting in your eyes.

• Metal parts heat up very quickly upon contact with a grinding wheel. Wear protective gloves prevent burns and injuries to fingers.

• If you are working with small parts, don't forget that there is a hand vice designed for every job.