BOULDERING STONE. - This name is applied by the Sheffield cutlers to the smooth translucent flint pebbles, found in gravel pits, with which they smooth down the faces of buff and wooden wheels, by abrading any large grains of emery, or other powder contained on their surfaces. See Wheels, articles 43 and 44. The bouldering stones are usually selected of about the size of a hen's or pigeon's egg, and of a flattened form; and the flat side becomes gradually worn down and smooth from its continual application. The term appears to be derived from the provincial use of the word boulder, to denote the round stones used in paving; whence, also, boulder-setter or pavior.
Metal laps are "bouldered down;" first, they are supplied with a little emery and oil, which is spread with the fingers, and then pressed into the metal and worn down fine and smooth with the bouldering stone, and wood laps are first anointed with flour emery or fine flour emery; they are then well bouldered, and are lastly waxed by holding a small piece of wax against the revolving wheel; these processes greatly reduce the cut of the powders; and unless the bouldering stone is plentifully applied the colour or high gloss cannot be produced on the works.