I was of the understanding (mistakenly?) that this would result in pins being too small - copper/water ratio being all wrong. No?:confused:

Bob

You could do it with a ball nosed endmill and plung drilling with it and then make the final run with a sqare ended endmill to make the bottoms flat. Drill bits, as I found out this weekend, are to flexable. Even with the mill they didn't make a perfect grid. One of the projects on my list is to use ball nosed endmills for the grid holes. Might make the pins to small though as pointed out. I will have to draw it out a few times and visualize. :D

oh ya... drill-bits are completely useless, for doing it this way.....

if the overlapping is such that the opening being formed between the 2 holes are not too big, (about 1 - 2 mm for a holesize of 5mm) then the Cu \ H2O ratio should still be exceptional.... The ratio is important, but what is much more important, is getting the pin shape right..... the resultant turbulence being created by a grid of properly shaped pins will instantly nullify any shortcomings as 'n result of a slight imbalance in the Cu/H2O ratio, up to a limit, of coarse.