06-10-2015, 05:12 AM
A typical belt grinder has 3 wheels -- a drive wheel, which is typically crowned, a tension idler, which is usually where the tracking adjustment is located, and the contact wheel, which is where the work is done. Contact wheels are typically mounted on a loose tool arm so they can be removed & replaced easily. The diameter of the contact wheel controls the shape of the hollow grind on a blade. You can buy contact wheels in 6" up to about 14" diameters. Contact wheels are often urethane coated to extend the life of the abrasive belt, and make grinding quieter. They need to be absolutely cylindrical, and concentric/parallel to the axle of the wheel or a poor finish on the knife will result.
Flat plattens are used to create flat bevels. Many of the cheaper grinders use mild steel bar stock as the platten which wears quickly. Higher-end grinders use hardened tool steel. Some knife guys use fire-proof glass, or ceramic. One guy has even made a water-cooled platten backer to both extend the life of the belt and reduce the frequency of water baths on the blade. The plattens are always considered consumable.
Flat plattens are used to create flat bevels. Many of the cheaper grinders use mild steel bar stock as the platten which wears quickly. Higher-end grinders use hardened tool steel. Some knife guys use fire-proof glass, or ceramic. One guy has even made a water-cooled platten backer to both extend the life of the belt and reduce the frequency of water baths on the blade. The plattens are always considered consumable.