Computer Numerical Control (CNC) Drilling is commonly implemented for mass production. The drilling machine, however, is often a multi-function machining center that also mills and sometimes turns.
The largest time sink for CNC drilling is with tool changes, so for speed, variation of hole diameters should be minimized. The fastest machines for drilling varying hole sizes have multiple spindles in turrets with drills of varying diameters already mounted for drilling. The appropriate drill is brought into position through movement of the turret, so that bits do not need to be removed and replaced. A turret-type CNC drilling machine is shown below.
A variety of semi-automated drilling machines are also used. An example is a simple drill press which, on command, drills a hole of a set depth into a part set up beneath it.
In order to be cost-effective, the appropriate type of CNC drilling machine needs to be applied to a particular part geometry. For low-volume jobs, manual or semi-automated drilling may suffice. For hole patterns with large differences in sizes and high volume, a geared head is most appropriate. If holes are close to each other and high throughput is desired, a gearless head can locate spindles close together so that the hole pattern can be completed in one pass. For further reference for CNC processes, please refer to the CNC, metal forming section.