Diamond Powder For Resin And Vitrified Bond Wheels

A bonded wheel is a compromise between two failure modes. If the grit is too tough it glazes, the wheel stops cutting and burns the workpiece. If it is too friable it wears out before the job is done. Resin bonds run cool and are forgiving on finish, so they are used for carbide tool grinding, glass edging and fine ceramic work; vitrified bonds hold form better and are specified for PCD and PCBN tool grinding; metal bonds hold the grit longest and are used where the priority is material removal.

The powder has to match the bond, not just the workpiece: a resin bond grips the particle mechanically, so a nickel-coated grit with a rough surface is held far better than a smooth crystal.

Choosing by operation, not by habit

On a resin or vitrified wheel the size ladder is wide and each band does a different job. Coarse bands take stock off; the middle bands do the actual grinding; the fine bands are a polishing operation disguised as grinding. Buying one mid-range size and hoping it covers all three is the most common reason a wheel is rejected.

Coated grit for resin bonds

Nickel-coated grit is the standard answer for resin-bonded wheels. The coating raises the effective surface area the resin can key into, shields the crystal from the heat spike at the cutting edge, and masks minor surface defects in the particle. The trade-off is cost, so it is normally specified on the finer bands where grit retention matters most.