The raw material - 5mm square brass rod. ![A new toy - a press drill](http://mdatblog.steamshift.com/images/uploads/2007/05//IMG_0542.jpg) The holes going through the rod were 2.5mm, with a 4.5mm countersink (to take No.2, 5/8" brass countersunk screws). So tolerences are tiny; there was no way I was going to manage this with a hand held drill. So I invested in this; a cheap (but actually pretty reasonable) press drill. This drill has no noticeable wobble or lateral movement, and was therefore able to drill the holes successfully.
Once cut to size and drilled, the brass rod looks like this. One of the challenges is how to enusre that these are all exactly the same length; the saw is too imprecise so I ended up cutting them all a little long and then filing them in batches in a small jig - even this though is not quite good enough. One option is to add a sprung contact on the bottom or top of each block to account for any imperfection.
Next up, the finished (for now) blocks.