Whenever the tool is not performing a machining operation satisfactorily, it is assumed that the tool has been failed. Normally when the tool fails the tool will be re-grinded to re-sharpen the tool, but in case of throwaway type of the tools, the tool will be thrown away and new tool tip will be taken.
Although the supply of sharp or re-sharpened tools is usually available from the tool rooms, tool changing operations are time-consuming and inefficient. The need for a more effective method has led to the development of inserts, which are individual cutting tools with several cutting points.
Drill bits tool made of High-Speed Steels material
Inserts are usually clamped on the tool shank with various locking mechanisms. Inserts may also be brazed to the tool body but because of the difference in thermal expansion between the insert and the tool body, however, brazing must be carefully done to avoid warping or cracking.
Clamping is the preferred method of securing an insert because each insert has a number of cutting points and after one edge is worn, it is indexed to make it available another cutting tip. The strength of cutting the edge of an insert depends upon its shape. The smallest the included angle, the lower the strength of the edge. Most of the inserts are honed to a radius of about 0.025mm to strengthen the edge.
Generally, the cutting tools made by using powder metallurgy as the manufacturing process, the hardness of tool is very high and can’t be resharpened by grinding operation. But these very hard cutting tools made by the powder metallurgy process can be re-sharpened by using the electrochemical grinding (ECG) process and the cost of ECG is higher than the new cutting tool itself. Hence it is not preferable to due to the reduction in tool changing time the production rate can be increased.
