What is necessary to prevent fatigue cracks in titanium after drilling?

Chamfering the holes is essential to prevent fatigue cracks in titanium after drilling because it helps to reduce stress concentrations at the entry and exit points of the drilled hole. When a hole is drilled, the material around the edges can be stressed due to the sharp transition from the hole to the surrounding material. This sharp geometry can act as a point where cracks initiate, especially under cyclic loading conditions.

By chamfering, which involves creating a beveled edge on the hole, the transition between the hole and the surrounding material is smoothened. This gradual change in geometry helps to distribute stresses more evenly, minimizing the risk of cracks developing over time due to mechanical fatigue.

In relation to other options, while applying a lubricant can aid in the drilling process and reduce friction, it does not address the stress concentration issue directly. Allowing cooling can help in managing thermal effects, but it does not inherently change the way mechanical stress is distributed around the hole. Using a powered tool can improve drilling speed and efficiency but does not influence the structural integrity of the drilled holes in the same manner that chamfering does.