Steam Bending Tips and Tricks
More advice on steam bending wood. October 2, 2005
Question
I've started to use my steam bending setup and have a few questions. My pieces are 10'-6" x 1-3/4" square. They're straight and square for approximately 38", then I've tapered 3 sides to a point 3/4 x 3/4". They have a 3-4' radius. Using the rule of thumb of 1 hour steaming for each 1" thickness, what measurement should I take from the taper? If I measure the thickest part, will a 3/4 x 3/4" point be over-steamed, and vise versa?
My supply of white oak for this project was air dried, but has considerable checking cracks. It's difficult to find 12' x 2 x 2" here now. I just steamed a piece and had failure on one edge, which I assume was from the checks. I steamed for 1 hour, 45 minutes. It bent okay, but I'm not sure if I should have steamed longer or shorter. Has anybody here had success steaming rock maple? I have a better supply of maple here.
Forum Responses
(Furniture Making Forum)
What kind of failure - compression/tension? Are you using straps and end blocks?
From the original questioner:
Failure was on the top side, inside edge of piece. It produced large slivers, bulges and seemed to follow checking cracks already in the wood. If it's the wood, fine, at least I know the reason for failure. But if it's time spent steaming, then I'm not sure how to judge time, as the piece is tapered. Do you steam for thickest or thinnest section?
I haven't ever steamed a taper. I suppose you would have to set steam time for the thickest section.
I have never had a problem over-steaming, so probably best to time for the thicker end. Straps with end-blocks are the way to better success. I guess the odd piece will crumple on the inside... beats those outside splits!
We have successfully bent kiln dried hard maple. The smallest radii was 12" and the parts were 1 x 2. You should cut your parts oversize, then machine to finish specs after the pieces have set. As far as the oak, it is much easier (for me) to shape wood after the bend. Understeaming is more of a problem for us than oversteaming, as you can always remove material after the wood has set. Straps and blocks are essential.
I have found, when steam bending kiln dried lumber, it helps a lot to get the moisture content up before steaming by soaking the pieces overnight in a tub of water. Also, I thought the ratio for time was one hour per ¼ inch of thickness. Could be wrong on that one - it’s been a while. The back straps and end blocks are necessary on tight bends.
