Which of the following is not a cause of excessive heat when drilling and reaming titanium?

Proper lubrication is essential in the drilling and reaming of titanium because it helps minimize friction between the cutting tool and the titanium material. When properly lubricated, the cutting edge of the drill or reamer is less prone to overheating, which is a common issue when working with titanium due to its tendency to work-harden and its poor thermal conductivity.

In contrast, high drilling speed, inadequate cooling, and incorrect drill bit selection can all contribute to excessive heat generation. High drilling speeds can increase friction and heat, while inadequate cooling fails to dissipate the heat generated during the cutting process. Additionally, using an inappropriate drill bit can lead to inefficient cutting and increased resistance, which also contributes to higher temperatures.

Thus, the presence of proper lubrication stands out as a factor that actively prevents excessive heat rather than causing it.