Wearing a modified Lou Box Dress.copper pipe for this necklace came from the plumbing section at Lowe's. Most hardware stores have precut short sections of small diameter copper piping for about $6. I tried this necklace with two different diameters of pipe. The one above is 1/4in inside diameter, the one below is 1/4in outside diameter. The smaller pipe is much easier to work with, and is probably the best place to start.
I was feeling pretty pleased with my $6 necklace until I saw what a pipe-cutter cost. The only one at our Lowe's was $40, pretty steep for a single DIY. Luckily, my husband has as many well stocked hobbies as I do, and he already has a very sturdy pipe cutter. If you don't see much plumbing work in your future, I think this $6 pipe cutter from Home Depot would be just fine. This copper piping is soft enough to bend with your hands, it would work with a cheap-o tool.
I used a Pyrex bowl to set the diameter of my necklaces. I experimented with parking bollards and street sign posts. They both worked just fine, but the bowl was way more convenient.
For the string, I cut a strip of cotton knit from my last cardigan. Any knit that rolls when you stretch it will work. I suggest a 1" wide strip, but you'll have to play with that to see what fits through the pipe. I prefer the rolled knit, to an actual cord because you can easily adjust the thickness to fit any size pipe. For both necklaces I made short "beads" from the pipe to add a little interest at the back.
DIY CURVED TUBE NECKLACE TUTORIAL