Abrasive Grains

Aluminum Oxide - Used for a broad range of applications, Aluminum Oxide is the most commonly used abrasive for general purpose work. Ferrous and non-ferrous metals, wood and solid surfaces.

Zirconia - Used for heavy material removal on all types of metals, Zirconia Alumina is a long-life premium abrasive that delivers aggressive cutting action while grit particles continually produce new sharp points. Great for titanium, hard steel and stainless.

Ceramic  - While producing outstanding results, Ceramic is a long-life premium abrasive, used for medium to heavy material removal on aerospace alloys, aluminum, carbon steels, nickel alloys, cast iron, forgings, and some stainless steels.

Silicon Carbide -  Used to obtain excellent results on concrete, stone, glass, plastics and very hard materials like titanium. A brittle self-sharpening grain.

Compact Grain - has a uniform scratch pattern, it is very strong, lasts a long time. It re-sharpens itself as it’s used.

Surface Conditioning color codes:

Coarse/Brown: For de-burring and heavy surface material removal

Medium/Maroon: For moderate to light cleaning, blending and surface material removal

Very Fine/ Blue: For removing fine scratch marks and lines, final finishing, polishing and preparing surfaces for painting

Super Fine/Gray: For finishing, buffing and fine polishing

Grinding wheel hardness
Hardness is rated from A-Z with 'A' being the weakest bond and 'Z' being the strongest.  A weak bond is preferred for grinding harder materials while a stronger bond is desired for softer materials.  A typical weak bond for steel would be in the 'F, G or H' range.  A medium hardness would be in the 'I, J or K' range. And stronger bonds in the 'L, M, or O' range.  Hardness is dependant on the grit type, the material being ground, the amount of stock removed, and a number of other factors.

Hardness grades are typically linear: If you increase the hardness by one letter grade (An H to and I for instance) it could give you double the wheel life.  Many people mistakenly believe that such a move (from an H to an I) would only be marginal -- Don't be misled here: A move of just one or two hardness grades could have a dramatic effect on your process!