Sharpening Carbide Tools
With excessive use it carbide tools will need to be sharpened from time to time in order to maintain their cutting edge. Cemented carbide indexable inserts usually require a special grind in order to form a contour on the cutting edge to suite a special purpose. Brazed type carbide cutting tools are re-sharpened after the cutting edge has become worn. On brazed carbide tools, the cutting-edge wear should not be allowed to become excessive before the tool has been re-sharpened. One method of determining when carbide tools need to be re-sharpened is by periodically inspecting the flank wear and the condition of the face, in addition, when amount of production decrease from that, which is usually achieved after re-sharpening is another indication that the tool requires re-sharpening.
Re-sharpening should never require the removal of more than 0.005 to 0.010 inch of carbide. The typical procedure for re-sharpening depends on the type of grinding operation that is required. If the procedure is to re-sharpen a dull tool, then a diamond wheel of 100 to 120 grain size is normally recommended. However, a finer wheel of 150-grain size is sometimes utilized in order to obtain a smoother finish. Some machine shops prefer to rough grind carbide with a vitrified silicon carbide wheel, the finish grinding is usually accomplished with a diamond wheel, with a final process designated as lapping may or may not be used to obtain an extra-fine finish.
Milling cutters can be sharpened by using the periphery of a disk wheel or the face of a cup wheel. The face of a cup wheel grinds the lands of the teeth flat, while the periphery of a disk wheel will leave the teeth slightly concave back of the cutting edges. The concavity created by the dick wheel will reduce the effective clearance angle on the teeth. This effect is more pronounced with smaller diameter wheels than with larger diameter wheels. It is for this reason that large diameter wheels are preferred for sharpening milling cutters.
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