—Two systems of drying are used in the bone department. The open air system for horns, selected white and striped hoof for manufacturing, shin bones, buttock bones, and those sold for manufacturing purposes; the coil, or room, drying principle, for grinding bone. The latter, crushed bone, is sold to glue makers and grinders. The usual method of handling the latter style of drying is to make platform coils or grids of 1¹⁄₄-inch pipe of an area convenient, as ten by sixteen feet, or units convenient to the space. These are in multiple and arranged to be accessible from two or more sides for convenience in filling and removing bones. The grids should be placed twelve or fifteen inches above the floor to permit cleaning underneath. The pipes or grids are usually substantially supported to carry the weight placed upon them. A wire screen of No. 5 screen 1¹⁄₄-inch mesh is a convenience to prevent bones dropping through. The bones are piled upon the grids to dry, when they are then transferred to storage rooms.
Crushed Bone.
—The skulls, jaws and larger bones, are usually crushed before storing so as to get a greater weight in less space. In this condition they are ready for grinding into “raw bone meal,” the name given to ground bone for sale to glue makers for extracting glue.
Grinding Bone.
—Ground bone is usually ground through an attrition mill, of which there are several types. The mill delivers the grindings to a bucket type endless chain elevator, which in turn passes it through a screen—shaking or revolving—preferably the latter. The screen is usually about three feet in diameter by twelve feet long and covered with a screening of No. 16 wire, eight meshes per inch, which screens it to a size that will readily pass through a grain drill. The tailings or over sized bone is returned to the mill for further grinding.
Neatsfoot Oil Storage Tank.
—This is preferably a jacketed tank, one tank within the other, and must be made with a jacket to withstand the pressure that may be applied. Consequently the jacket should be reinforced with stay bolts so as to prevent distortion when pressure is applied. Any and all oil settling vats are best made cylindrical in form with a sharp cone at bottom. The cone is equipped for withdrawing sediment at the bottom and for withdrawing oil for purification sufficiently high in the cone to avoid withdrawing any sediment.
Neatsfoot Oil Purifiers.
—The same type of kettle or tank as described above is required, the latter being sufficient in size to accumulate a week’s work.