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characteristics of nut shells and fruit pits all shell products do not necessarily meet the same specifications, nor have the same uses. Industrial Cleaning and Finishing Oil, dirt, corrosion products, stain, paint, grease and the like can be removed from metal surfaces by air-blasting with soft grits prepared from shells of walnuts, pecans, peach pits, and similar residues. This method was developed originally for the Navy to use grits from corn-cobs for cleaning aircraft engines and parts. The method is inexpensive and foolproof because surfaces are cleaned without change of dimensions. No pitting or abrasion, such as produced by sand blasting, occurs. The method is particularly useful with mild steel, nonferrous metals, alloys, and parts that must be maintained at close tolerances. Modifications of the blast method are used in finishing molded plastics, metal die-castings, and machined parts. One manufacturer of precision instruments states that his company saves $100,000 a year in finishing parts with shell grits. Many stamped metal articles and molded plastics are deburred, cleaned, burnished, and polished by tumbling in drums containing shell grits. Various grades of grits are required depending upon the nature of the pieces being finished. Fillers for Plastics and Plywood Glues The Laboratory has studied the use of shell flours for use in plastics and plywood glues. Many of these flours are now in regular commercial use. Flours for these applications are prepared in various grades, all finer than 100-mesh. Use of these flours not only improves the properties of the final products but also reduces the cost of the products. Molded plastics prepared with fine flour from English walnut shells have exceptionally fine surface finish. Insecticide Carriers The insecticide field provides a good outlet for shell flours. Flour from walnut shells was the first of this type of material to be used for this purpose. Often the active ingredient in a finished insecticide is present in quantities of less than 1 percent. Custom grinders should plan to recover the flour as a co-product of their operations rather than attempting to grind to flour alone. Explosives Large amounts of shell grits and meal are used as diluents in the manufacture of dynamite. Material for this use ranges in size from No. 10 to No. 100, the requirements of the individual manufacturers falling within much narrower limits as to si
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