A “blind holes” is that has only one point of entry and does not pass through to the other side.
Cleaning blind holes require proper positioning of the components such that the cleaning media enters as well as drains properly. If the blind holes are facing the bottom of the tank, the cleaning media will not completely fill the hole because of air entrapment. If the blind holes are facing the top, the cleaning media will not drain out from these holes easily.
This is why component placement plays the utmost importance in effective part cleaning and drying.
Ultrasonic cleaning is most effective method of cleaning blind holes as the sonic waves reach even the most complex part geometries.
The next step after cleaning is drying. This requires the liquid to be completely drained from the blind hole as the puddle of water is much more time consuming to dry compared to thin layers of water.