Performance of Reground Tools in Drilling
The present work evaluates the performance of step drills, new and after regrinding. The tools were made of P20 cemented carbide coated with TiAlN. The routine of re-coating them after regrinding were varied (no recoating, recoating over the previous coating and recoating after removing the previous coating). The output parameters considered for determining the machining performance were: tool life, thrust force, torque, form errors (roundness and cylindricity) and surface roughness (Ra and Rz parameters). The results generated with the resharpened tools were compared to those obtained with a new tool (first time used). The results showed that in general the reground tools showed worse performance than the new tools, regardless the parameter considered. Only the tools that have undergone the process of cleanness of the previous coating and then reground and recoated (with the same type of coating) showed results similar to the new tools. The tools with no recoating and those that received the recoating over the previous showed, practically in all tests, higher thrust force and torque, larger form errors and worse surface roughness than the new tools.