How to Choose the Right CBN Grinding Wheel for Hardened Steel

Cubic boron nitride (CBN) is the second-hardest material known and the abrasive of choice for grinding hardened steels, tool steels, and high-speed steels. Choosing the right CBN grinding wheel is about matching the bond, grit size, and concentration to your material and the finish you need.

Why Choose a CBN Grinding Wheel?

CBN wheels are classified by their bond type. The bond holds the CBN grains and determines how the wheel wears, cuts, and cools. Three bond types dominate: resin bond, metal bond, and vitrified bond.

Resin bond CBN wheels are the most economical and versatile. They grind cool, are easy to dress, and are widely used for tool and cutter grinding and general-purpose work on hardened steel.

CBN Wheel Bond Types: Resin, Metal, and Vitrified

Metal bond CBN wheels use a sintered metallic matrix that holds grains firmly for maximum wheel life and stock removal. They are the first choice for high-production grinding, heavy roughing, and difficult materials such as hardened dies and superalloys.

Vitrified bond CBN wheels combine a porous, self-sharpening structure with excellent coolant flow. They deliver fine finishes and low grinding temperatures, making them ideal for precision internal, external, and form grinding.

Grit Size and Concentration: What You Need to Know

• Resin bond: Economical and versatile, ideal for tool and cutter grinding with good finish and easy dressing.
• Metal bond: Highest strength and longest life, best for heavy stock removal and high-production grinding of hardened steel.
• Vitrified bond: Porous, self-sharpening, and coolant-friendly, preferred for precision internal and external grinding.
• Grit size: Coarse grit (B91-B126) for fast removal; fine grit (B46 and below) for smooth finishing.
• Concentration: Higher concentration gives more cutting edges and faster removal but a harder wheel; lower concentration suits finishing.
• Coolant: Always use adequate coolant to control heat and prevent workpiece burn when grinding hardened steels.
• Dressing: Metal and vitrified CBN wheels need proper truing and dressing with diamond tools to maintain geometry.

Which CBN Wheel Should You Choose?

Grit size and concentration complete the specification. Coarse grits remove material fast; fine grits produce smooth surfaces. Higher concentration packs more cutting edges for faster removal, while lower concentration suits finishing and contour work.

For grinding hardened steel and tool steels, a metal or vitrified bond CBN wheel usually gives the best balance of wheel life and finish. Always run CBN wheels with adequate coolant, and true and dress them with proper diamond tools.

Not sure which CBN wheel fits your job? Send us your workpiece material, hardness, wheel shape, and grinding parameters. Our engineers will specify the right CBN wheel for your application.