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Truing
To make level, balanced or concentric; bring or restore to a desired mechanical accuracy or form. To prevent vibration at high speeds, a diamond or other dressing tool is used to ensure that a non-woven grinding wheel is round and concentric.
Dressing
Removal of undesirable materials from "loaded" non-woven grinding wheels to expose unused abrasive points.
Both activities are limited to convolute wheels 6 inches in diameter and larger.
Methods
Truing or Dressing for non-woven/convolute wheels can be accomplished by either Powered Diamond Saw Blades, Coated Abrasive Materials or the use of Custom Metal Tools. The best two options of these for end users are either the Coated Abrasive Materials or the Custom Metal Tools.
The Coated Abrasive Materials option combines inexpensive material with a little technique. A piece of very coarse (24 or 36 grit) coated abrasive material and a heavy solid piece of metal is used. The coated abrasive material is used because of the many cutting points it provides for truing. The heavy piece of metal maintains contact between the non-woven wheel and the coated abrasive material. If a heavy piece of metal is not used, the coated abrasive material will bounce on and off the non-woven wheel, and the wheel will not be properly trued. This method works best for the harder-density non-woven wheels, such as the convolute 9SF for deburring.
The Custom Metal Tool option is the most unique method because some operators use many different variations of "truing tools"- ranging from a bottle cap to a very elaborate two-handed rake-type tooth tool. The tools are usually very thin to maintain a sharp edge, short, and have a right angle to reduce the change of snagging the tool with the wheel. This method is best suited for softer non-woven wheels. The advantage of this method is the tool’s ability to quickly cut into the wheel by actually cutting the non-woven fibers.
Profiling
Profiling, which is often inaccurately referred to as "dressing", is putting a mirror image of the one to be sanded into the face of the sanding wheel. This procedure is not recommended for convolute wheels. There are specialty non-woven wheels made by companies like Bardo-Flex which are specifically designed in the weave to allow profiling.