General Cutting Tools aka Cutting Tools Chicago is your one stop source for all your carbide cutting tool resharpening, regrinding, and refurbishing to like new condition. Cemented carbide indexable inserts are usually not resharpened by sometimes they require a special grind in order to form a contour on the cutting edge to suit a special purpose. Brazed type carbide cutting tools are resharpened 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 is resharpened. One method of determining when brazed carbide tools need resharpening is by periodic inspection of the flank wear and the condition of the face. Another method is to determine the amount of production which is normally obtained before excessive wear has taken place, or to determine the equivalent period of time. One disadvantage of this method is that slight variations in the work material will often cause the wear rate not to be uniform and the number of parts machined before regrinding will not be the same each time. Usually, sharpening should not require the removal of more than .005 to .010 inch of carbide.
General procedure in carbide tool grinding. The general procedure depends upon the kind of grinding operation required. The operation is to resharpen a dull tool, a diamond wheel of 100 to 120 grain size is recommended although a finer wheel – up to 150 grain size – is sometimes used to obtain a better finish. If the tool is new or is a standard design and changes in the shape are necessary, a 100 grit diamond wheel is recommended for roughing and a finer grit diamond wheel can be used for finishing. Some shops prefer to rough rind the carbide with a vitrified silicon carbide wheel, the finish grinding being done with a diamond wheel. A final operation commonly designated as lapping may or may not be employed for obtaining as extra-fine finish.
Wheel Speeds: The speed of silicon carbide wheels usually is about 5,000 feet per minute. The speeds of diamond wheel generally range from 5,000 to 6,000 feet per minute; yet lower speeds (550 to 3,000 fpm) can be effective.
Offhand Grinding: in grinding single point tools(excepting chip breakers) the common practice is to hold the tool by hand, press it against the wheel face and traverse it continuously across the wheel face while the tool is supported on the machine rest or table which is adjusted to the required angle. The is known as “offhand grinding” to distinguish it from the machine grinding of cutters as in regular cutter grinding practice. The selection of wheels adapted to carbide tool grinding is very important.