How to Choose Grinder Wheels
Whether you're replacing a worn-out grinder wheel or simply upgrading one that doesn't meet your needs, it's important to get the right one to minimize sharpening time and maximize the life of your tools and grinder wheels. Manufacturers make grinder wheels from different abrasives to work best with specific types of metals.
Types of abrasive wheels
■ Silicon carbide. This low-cost wheel works best with non-ferrous metals, such as aluminum, brass or copper, and carbide. Typically, wheels are dark gray to bronze in color. Although they used to come standard on most bench grinders, they're becoming less common as more manufacturers switch to aluminum oxide wheels.
■ Aluminum oxide. Priced at 20–30% more than silicon-carbide, these general-purpose wheels come in two grades. The lower-cost version, usually gray or brown, works best with carbon-steel tools (the most common steel, usually associated with low-cost tools). The white version typically sells at a slightly higher price, but cuts faster while heating the tool less. It breaks down quicker than "regular" aluminum oxide to continually expose a fresh cutting surface, which means replacing it more frequently. This premium blend also works with carbon steel, but it's best with harder steel alloys.
■ Ceramic/aluminum oxide. Most often pale blue, this abrasive has a fast cutting action with the least amount of tool burn. It's more durable than the white blends (and about 25% higher in price), and it's ideal for hard steel alloys, such as high-speed steel (HSS).
■ Cubic boron nitride. This abrasive is bonded to a steel wheel. Use it only for hard steel alloys and carbide tools; carbon steel will damage the abrasive. Sold in multiple grits, it costs 4–5 times that of aluminum-oxide wheels.
When to change wheels
Replace a wheel on your grinder if any of the following apply:
■ The gap between the wheel and tool rest (below) cannot be closed to 1⁄8 " or less.
■ The gap between the wheel and spark arrestors cannot be closed to 1⁄2 ".
■ The wheel shows any indications of damage (below).
How to get the right grit
A grinder with two abrasive wheels (versus one with a single abrasive wheel and a wire wheel) allows you to use a coarse wheel for shaping and a finer one for honing.