What USB/Serial lead have you got?
There was an issue recently with FTDI clones, and FTDI releasing a windows driver that bricked them.
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I'd guess the screen will be capacitive, but the quick check is to try working it with something like the blunt end/top of a pen.
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Alu/brass, figure out what you need and do some searching. If you'll be buying full lengths/sheets, it's often worth trying your local metal suppliers. Personally, I use a mix of local for full size bits, metalsandplastics for cut alu/brass bars, and ebay for odds and ends for one off projects.
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Endmills I mostly use APT (shop-apt.co.uk IIRC), as I know I'm getting decent cutters. Ebay is cheaper, but I've found quality can vary. Before you buy anything, run some figures through FS Wizard / G-Wizard (I personally prefer FS Wizard/HSM Advisor as HSMA I think is easier to use/configure) and try out different speeds/sizes/flutes and compare to what power/feedrates you have available. On a Triac, I'd guess you'll be wanting 2 flute to keep a decent chipload for the given RPM/feedrates, but run the figures and see.
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Holding Kits, you can't really go wrong with the generic T-slot kits from ebay as a starting point. Once you get going and have some experience, you'll probably find you'll want to invest in other mounting methods depending on what you're doing. I'm just in the process (was, I'm currently waiting for a helicoil kit after I picked up a 4.8mm drill instead of the 4.2 to make a couple M5 threads) of making up a work plate that'll use Mitee bite clamps to hold flat bar in place, as I'm fed up with clamps being in the way and needing extra material to clamp.
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For other bits, ArcEuroTrade is good. Not the cheapest, but they're stuff is always good quality, unlike some of the ebay offerings. They also dispatch quickly. Personally, just buy what you need when you need it. I've got stuff I bought years ago that I thought would be handy, but has never been used. On the other hand, it can be annoying not being able to get a quick job done because you've not got that couple pound widget that would make it so much easier!