I recently found an old, wooden swing seat in a scrapyard where it was serving as one side of a planting trough. I love its dark, fissured surface because it reminds me of happy childhood days spent in playgrounds made of wood, before they got all plasticky. There's nothing like the satin warmth of old playground timber worn smooth by generations of kids (and, I'm sure, many adults too!)
I'd like to share here my (total beginners) experience with using copper pipe for furniture - you can get by with much simpler, cheaper joining techniques because furniture is much more forgiving than plumbing.
This is my first Instructable and I'm really pleased to finally give back to the community that's helped me so much with many projects!
Step 1: Preparing the Wooden Seat
I won't dwell on this, there's a lot of information about how to prepare old barn timber. Here's my conditioning process:
1) Wash thoroughly with soap, water and a scouring pad. Be sure to flush out all the grit from the fissures (this piece had some fauna, too). Let it dry out fully.
2) Once over with 200-grit sandpaper. Keep this step light, you don't want to remove the patina.
3) Seal the wood with a satin-finish stain. Kimber-O wood dye (Ebony) matched the color of the wood fairly well.
The final surface should be smooth to the touch while retaining its deeply fissured texture.
Step 2: Choosing the Material
I used BS EN 1057 HH 15 x 0.7 copper tube. HH means hardened, and has 15 mm OD and 0.7 mm wall thickness. It held up well structurally, but can also be cold bent if you need angles that you can't get with elbows (45 and 90 degrees). Cost (in Singapore) is $10 - 15 for 9 ft and joints are about $0.60 - 1.00 each.
I was able to complete my design with just elbows and T-joints, which simplified things a lot.
I'm including my design measurements in case they work for you.
Step 3: Cutting and Joining
To cut metal tubing it's best to use a pipe cutting tool - it's cheap and beats using a hacksaw! Simply position the circular cutting blade where you want to cut the tube, tighten it slightly but not so much that it starts to bend the pipe. Rotate the tool a full revolution around, then tighten the blade some more. Repeat till it falls apart, then use a reaming tool to remove the sharp edges.
Typically, copper pipe is joined to elbows by soldering, also called 'sweating the joint'. I didn't want to buy a butane torch, so I tried using metal-filled epoxy instead. I used 150-grit sandpaper to roughen the ends of the copper tube and also the inside of the elbow joint to ensure that the epoxy could grip the metal surface.
Then, apply epoxy to the inside of the elbow joint, insert the pipe end and twist several times to make sure the epoxy is evenly coated. I tried using a bench vise to pull it apart and the joint held true, so I was quite pleased with the result structurally - I can't attest to its watertightness but it's good enough for furniture.
One other thing good about using epoxy is that the looseness of the elbow joint also lets you put a slight tilt in the tube, ~ 5 degrees off the vertical. This was perfect for my purposes since I had designed the chair legs to be slightly tilted and so I was able to avoid tube bending.
Step 4: Putting It All Together
I fastened the chair legs in two different ways. The main loop is fastened directly through the tube diameter, while I had a side support fastened with a flattened pipe end.
I used a bench vise to flatten the pipe end. If the length of tube you want to flatten is longer than the jaws of your vise (like mine), I would recommend flattening it in stages: half flatten the entire length, and then go back and fully flatten the pipe. Doing this avoids splitting the tube sides.
Once flat, the tube is easily bent with the help of the vise.
Fasten the bench legs to the wood and you're done!