Grinding wheel size: sand size

Abrasive Surface Grinding Wheels is your good choice.Knowing the type of abrasive, the next question is "particle size": particle size
Each grinding wheel has a number that represents the characteristic. The particle size refers to the size of a single abrasive particle in the grinding wheel. This number corresponds to the number of meshes contained in a one-inch square screen. In other words, a large number means that the sieve through which the abrasive passes is small. (Fine abrasive)
A smaller number (such as 10, 16 or 24) indicates that the abrasive used for the grinding wheel is coarser. The coarser the particles, the larger the pieces of workpiece that can be removed. Coarse abrasives can be used to quickly remove the volume of the workpiece, but the surface roughness is poor.
Larger numbers (such as 70, 100, and 180) indicate that the grinding wheel uses finer abrasives. Fine grinding wheels are suitable for processing materials that require fine surface roughness, small contact surfaces, or hard and fragile materials. Abrasive Surface Grinding Wheels is your good choice.