on the straight cuts'...
to make manufacturing these blocks feasible for doing with a cheap drill-press, you need to avoid having the holes cut into one another. that means that there will be a very thin wall sealing each hole, from the 4 around it. Now for fluid to be able to get through this grid, we need to remove these thin walls... hence the need for the Dremel... by having the holes in a square grid, one only need to cut in 2 directions, in order to form the pins. and make way for the fluid to get through..
the trick comes in being as precise as possible, the more accurate you can get the holes drilled, the thinner the walls will be, and the easier the dremeling will be. on a manufacturing cost table, the Dremel disks is the third most expensive consumable in the process... needless to point the savings by being accurate....
