First off, check out my how-to vid, and a few sample sliding shots...
At the basement of my consignment shop, I found a big bucket of these heavy-duty, chrome-plated hangbars that I had bought from our local Steve & Barry's when they went out of business. You can find these rails at most store supply places, and online for less than $5/each. What these have going for them over your run-of-the-mill conduit, is that they're chrome-plated (duh!) and very smooth.
Sooo.... I took Lolo's idea and went with EMT couplers, and lined these with some drawer felt, making the sliding action on the rig... "like buttah." In parts, I spent less than $50. If you don't have some common tools on-hand (drill bits, files, hole saws, etc.), you're gonna spend a LOT more... but you'll then own some great DIY tools that you can use forever.
Since I don't have a drill press, drilling the electrical box cover was, by far, the most painful exercise. It requires a bit of exactitude to line the hole in the couplers up with the ones you need to drill in the plate.
No matter what you do, use layout lines and a heavy punch to start your work on the steel parts, or you will be frustrated watching the drill bit dance all over your work... and NOT get the holes in the right place. Like with any metal drilling, starting with smaller bits, working slowly (without too many RPMs) and having some cutting oil on-hand will make for a much more satisfying experience.
Who doesn't want to make their work better, right? I notice that the ends of the slider sag a bit under the weight of my Canon 7D and Tamron 17-50 VC zoom. I think that I'll want to make slider 1.1 a bit more stable for shoots when I do have extra time on-location to set up a couple of heavy-duty lightstands on each end. In the field, and on "run & gun" situations, I can either use my DIY DSLR cage and replicate slider moves, or deal with the small amount of flex. I could also use a prime lens, like my Canon EF 50/1.8 or my vintage Kiron 28/2, which weigh a LOT less than the Tamron zoom.
Have fun, and comment on my YouTube video above, if you have some ideas or suggestions.
Brian Brown BrownCow Productions
If you're bored, check out my website for all about me and my video production business.