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)
Hi, I'm Dave Osborne. With over 50 years experience as a journeyman carpenter, foreman and contractor in heavy construction I enjoyed working with apprentices and sharing the tricks of the trade that others shared with me. Now I get emails from Members all over the world and we include many of my answers in our Free Monthly Newsletters. Some of my answers include drawings and instructions specific to a project, but may also answer your questions. I use correct construction terminology, so you can confidently inform your building supply dealers or contractors exactly what you need.
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