Nice work, though I would seriously suggest making some plastic covers that enclose the entire copper bus aside from the breaker points, and which allows you to have an insulating spacer to keep the bars apart. with DC busbars the problem is that once an arc starts it tends to burn until it melts the whole bar away into vapour. A bar of white glass filled nylon ( Available from Maizy plastics nationwide) or SRBP, whatever is your choice, will be both machinable with regular tools ( though the glass filled nylon needs carbide milling cutters, and is murder on regular HSS drills and tooling) you can tap holes in it to have screws in from either side, staggered at least 4 hole diameters, and no more than half way through the material, so that you can use some stainless steel capscrews to hold the bars together in a block. You can also use them to hold a top and bottom cover in place made from thinner SRBP material, or bare FR4 PCB material.
SRBP is also known as Bakelite, a brown resin impregnated cloth which is used to make distribution panels. More stable at high temperature than the glass filled nylon, though it is more brittle.
If you are tapping threads into the soft copper I would recommend leaving a close clerarance hole instead and using a Belleville washer ( available in a few sizes, you do get them from Action bolt here in Durban, and BMG will probably have them, though the ones I needed a while ago were not so I ordered them from the UK at a horrid price and courier cost) to apply a constant contact pressure on the contact surface so it does not loosen with creep. As well some dielectric grease on the bolt threads and the shiny clean mating surfaces to keep them good contacts will help a lot.
