Measuring 12" x 4-1/8" x 1-1/8" high and weighing approximately 14 lb, this is one substantial lapping plate! Made from an iron chosen for its dimensional stability and material consistency (you won't find blade-scratching carbides in the material), the bottom and sides are machined, and the top is ground flat to within 0.001" over the entire surface. The unique channel design, optimized for a figure-eight lapping pattern, serves to eliminate resistance from hydraulic lock and captures excess oil, abrasive and slurry. For fingertip safety, the channels have been chamfered to eliminate sharp edges and corners. Not intended for heavy material removal, it is designed to condition or smooth previously ground surfaces and is used with light mineral or honing oil and silicon carbide (SiC) abrasive grit. We offer a range of grits, but we recommend 280x for twisted, wavy or linished objects, 400x for ground surfaces with a slightly rough texture, and 600x for surfaces requiring little material removal. While any grit size will ultimately achieve the same end result (since particles become progressively finer during the lapping process), the coarser the abrasive, the longer it takes to achieve a smooth surface. A useful tool for improving the surface quality of plane soles, blades and chisels, it will lap materials up to the same surface area of the lapping plate, accommodating even a jack-plane sole.