inspection and finishing.
Certain metals, such as aluminum, are susceptible to dragging by dry abrading, but a light tip dressing
of a low free-grease content buffing bar will sufficiently lubricate the surface and produce an even finish.
In this case, care should be used so the lubricant does not penetrate the layer of greaseless compound
and saturate the cloth, which will prevent the proper adhesion of subsequent additions of greaseless
compound.
Binders for grease base buffing compositions are composed of fats and waxes of animal, vegetable,
and mineral origin. Some of the more commonly used are stearic acid, hydrogenated fatty acids, tallow,
hydrogenated glyceride, and petrolatum.
The fatty acids under conditions of buffing seem to have, in addition to their physical properties, a
beneficial chemical effect in the formation of metallic stearates.
Cut-down buffing bars combine fast cutting buffing powders in a grease base binder formulated to give
a great amount of grip to drag between the wheel and the metal surface. Powder to binder proportions
varies with the type of work, the condition under which it must be done, and the oil absorption of the
buffing powder.
Careful study of the individual buffing operation is necessary to decide on formulation. The metal being
buffed in a cut-down operation determines which buffing powder to use. Cut down compositions for
non-ferrous metals most frequently contain once ground Tripoli. It Performs very efficiently and is
relatively inexpensive.
Cut-down buffing bars for carbon and stainless steels are generally based upon fused and unfused
aluminum oxide. Such compositions are sometimes recommended for use on some of the aluminum
alloys, particularly parts made by casting or extrusion. Under certain conditions, a cut-and-color buffing
operation is used in place of the cut-down and the highest coloring operations. Since fast cut is not a
prime requisite, the cut-and-color compound binder is of the same general type as above, but with less
drag.
Moderately cutting abrasive powders are selected to give some brilliance with moderate cut, thus
sacrificing both cutting and coloring properties to produce a general-purpose composition.
Cut-and-color compositions for nonferrous metals contain white silica powders, or a blend of these
powders with Tripoli. Similar compositions for the ferrous metals contain coarse unfused aluminum
oxide powders or a combination of fused and unfused aluminum oxide powders.
On certain nonferrous articles, cut-and-color buffing is done with a crocus bar containing a coarse
graded iron oxide powder. Producing a color, luster, or mirror finish on metals requires the use of
compositions composed of the finest abrasive powders so a minimum of scratches will show in the final
finish.
Fast cutting is not required in such operations, and hinders are formulated primarily to hold the selected