Shapton's diamond glass lapping plate (DGLP) is a measuring tool. The plate is created by imbedding diamonds in the surface of a solid plate of high precision float glass. The surface of the plate is calibrated to a spec that exceeds plus or minus 5 µ. A micron is the thousands of a millimeter. The total deviation in the surface of the lapping plate falls in the range between zero and 10 µ. This is measured with special equipment in a clean environment in the Shapton factory in Japan. This calibration is performed before the diamonds are attached to the surface of the plate. Once the diamonds are attached to the surface of the plate, the surface of the plate can no longer be measured with equipment available today. However, a stone that has been flattened with the plate can be measured. At the factory, we regularly measure stones that have been flattened with the DGLP to plus or minus 1 or 2 µ. After considering the level of technology used to create the DGLP, the price is much easier to understand.
Why is a flat stone so important? If your stone is not flat, you cannot consistently shape the edge. Imagine having a dip in the stone and a dip in the knife produced from using the steel constantly in the kitchen. The dip in the stone and the dip in the edge of the knife would work against each other making it very hard to get the bottom of the dip in the knife to contact the surface of the stone they just really couldn't mate up to each other. The flatter the stone is, the easier it is to have the edge mate up with the surface of the stone. Additionally, the flatter the stone is, the more abrasive you will come in contact with while you're sharping. The more abrasive you can come in contact with as you're sharpening, the faster you're sharpening is going to progress. Sharpening is really a process of sculpting. You are sculpting the edge on the stone as you're working. A flat stone will help you go much faster and at a stone that's more resilient is going to help you shape the edge or form the edge more easily than a soft stone that conforms to the shape of the edge. If you're using a stone that is soft enough to wrap itself around an edge, you will not be able to shape the steel efficiently. A flat resilient stone will help you maintain crisp geometry. The Shapton Diamond on Glass Lapping Plate (DGLP) is designed to keep your stones flat throughout the sharpening process.