A steam box is needed to bend wood to rounded shapes without breaking the fibers of the grain. Steaming wood softens the fibers, making them bend around a mold easily.
I needed three pieces of molding bent around a staircase when I was building my house. This is how I made a simple steam box.
The steam box consisted of a 10 foot length of 4" PVC pipe I had left over from the perimeter drainage around the house. This was the solid pipe not the one with the holes in it. The wood I used was standard 2 1/4" oak casing. I used this as a base around the walls. I was to paint the base and keep the other two pieces clear and natural. I went with oak even though I was going to paint it because I knew that oak was very easy to bend. My dad who bent large ribs for a boat purchased Indiana oak, I think it was, for bending in his steam box. He actually gave me the idea of building this steam box.
For the source of steam I bought an 8' length of 1/2" inside diameter soft copper pipe and bent it around the 4" PVC, three or four times, to make a coil. On one end I attached a compression fitting with 1/2" male pipe thread. I then adapted this to fit a standard garden hose thread. I have a "Big Bertha" propane torch, which you can rent, which I hooked up to my barbeque propane bottle. I inserted the open end of the coil into the open end of the pipe, stuffing rags around it. I heated the copper coil with the torch while having the water run slowly through the garden hose. Soon it became steam. I put the pipe on a slight slope, so the water and steam would drain out the other end. I stuffed some rags around this end, as well, to slow the escape of steam, not too tight, though. After about 20 minutes, the casing was pliable to bend around a 4' radius. I brought it out and nailed it in place immediately. It cools quickly, so be ready. I noticed after I was done that the PVC pipe got soft and changed its shape, so don't expect to reuse the pipe again.
It worked well. Thanks, Dad!
Dave(Ask Dave) (About Dave)
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