Deep hole drilling applied to square blocks is special. Depths up to three meters can be reached by drilling from one direction. Diameters from 30mm u/I 200mm have been performed.
Round axes are usually internally machined on a lathe so the axe is the turning part. At deep hole drilling, the work piece is fixed with allows you to deep hole drill the most advanced pieces of equipment.
Complete header blocks have been drilled by this method. Can you imagine the saving on welds.