If you’ve been around grinding wheels for any time, you certainly know what they look like and what they do. But have you ever wondered about what goes into a grinding wheel? Well I have so that’s what we’re going to talk about today.

Here’s the short version:

  • Abrasive
  • Grit
  • Grade
  • Structure
  • Bond

Now we’re going to look at each of these components individually, starting with Abrasive.

Abrasive is the material from which the wheel is made. This is what does the work. Most common abrasives include, Aluminum Oxide, Silicon-Carbide, Zirconia Aluminum Oxide, Cubic Boron Nitride (CBN) and Synthetic Diamond. Each has it’s characteristics and applications which we won’t talk about here. We’ll save that for another time.

Next is Grit. This is the size of the abrasive grain in the wheel. As you probably know, the lower the number, the coarser the grit. Coarse grits are used for soft, pliable, stringy materials when you want fast material removal, have a large contact area and high pressure. Finer grits are used to produce smooth finishes and when you’re grinding hard, brittle materials and have a small contact area.

  • Coarse grits are 8, 10, 12, 14, 16, 20 and 24
  • Normal grits are 30, 36, 46, 54, 60 and 70
  • Fine grits are 80, 90, 100, 120, 150, 180 and 220
  • Very Fine grits are 240, 280 and up

Grade refers to the strength of the bond (we’ll get to bond in a bit) that holds the abrasive grains together. This can range from very soft to very hard and is represented A to Z in grinding wheel specs.

Softer grade wheels cut faster with less chatter. They require lower amps or power to drive them, have shorter wheel life and produce a worse finish. Harder grades cut slower with more chatter. The produce a better finish and have a longer life, but require more power/amps to operate.

Structure denotes the spacing of the abrasive grains in the wheel. The lower the structure number, the denser the wheel. Structure numbers range from 0 to 14.

The final component we’ll look at is the Bond. As the name implies, this the material that holds the abrasive grains together in the wheel. There are several common types of bond – Vitrified, Resinoid, Epoxy and Rubber. Each of these bonds has it’s own characteristics and applications. We’ll touch on those in another post so that we can go into more detail.

Standard Abrasive Wheel Markings