Just for interest :
Whilst it is true that drilling a hole will inhibit crack propagation in some circumstances and in some materials it is not the universal cure it is always claimed to be – often the crack will just change direction . It only really works in ductile materials with very moderate stress levels .
Use of the drilled hole in wood is fascinating – sometimes a crack will stabilise for hundreds of years and sometimes it will grow at visible speed and split plank completely .
There is a whole section of stress analysis dealing with crack propagation and a whole branch of NDT for detecting and monitoring cracks . Understanding how cracks form and grow is of particular importance in the Aircraft , Nuclear and Process Chemicals industries .