5mm is tiny
I'd sooner invest in the spot welding tools.
It can be done, but I would suggest doing it outside to be safe. Set the depth stop on your drill press so you can't go too deep.
You will need a normal tap to get started and a bottoming tap to finish threading the hole all the way to the bottom. 5mm is not a lot of thread to work with in soft aluminum. Those terminals are intended to have bus bars laser welded to them.
You can get handheld spot welders intended specifically for battery terminals for US$30-50. Spot welding is a lot less likely to damage the cell or risk puncturing it. Here's an example:
I don't think those would work for these large batteries. I have one that I use for small cells though (i.e. 18650/21700).
OK, I'm no expert but it says this at the end of that product listing:
Secure this matched 2-pack of premium Sunwoda 314Ah cells—fresh stock from a respected brand, with flat studs for easy welding/integration.
Are you saying they need a heavier gauge bus bar for the current, something too thick for a small spot welder? Would you MIG/TIG weld a battery contact?
Yeah, these are 0.5C cells, meaning they can safely discharge 157A (I would be using them for offgrid solar), so those little nickle strips would melt. I think TiG welding these would be extremely dangerous and produce too much heat (and I've never TiG welded before; just badly MiG welded a couple times). By "welding" in the description they mean commercial laser welders.
For questions about component-level electronic circuits, tools and equipment.
1: Be nice.
2: Be on-topic (eg: Electronic, not electrical).
3: No commercial stuff, buying, selling or valuations.
4: Be safe.