Steam-Bending a Pre-Turned Part
Bending wood that has already been turned is difficult, if not impossible. August 6, 2010
Is it possible to steam bend a piece of wood that has already been turned, as opposed to turning a square or rectangular blank?
(Furniture Making Forum)
From contributor R:
It's still wood, right? Still has lignin in it? Bend away.
From contributor L:
It depends on a long list of variables, but in general, I'd answer a qualified yes. Know that as the piece bends, it flattens a bit, so instead of a round turning, you wind up with an oval shape. A photo or drawing showing species, turning pattern, size and radius would help. And that's only the beginning.
From contributor H:
If the turning is anything but a round dowel, you will have trouble. The thicker parts of the turning will not give as easily as the thinner parts. So expect the thinner, smaller diameter areas of the turnings to break or crack, leading to an uneven bend.
From contributor T:
I made some chairs once that had a curved square leg at the bottom and were turned at the top. I cut the curve first and made a jig that held the square part of the leg on the lathe for turning. It's a traditional technique you will find in turning books. Steam bending a turned piece won't do the finished turning any favors.
From contributor C:
It can't be done unless it is very gentle, it wasn't kiln dried, and you have a suitable bending species. Here is why... Your turning is probably from KD wood. If it is green, or partially air dried, you have half a chance to get a modest bend. Wood that is KD is past its prime for bending, though there are some exceptions for modest bending needs. Target 15 to 25% MC for bending. Then, consider that steam bent parts need a backing strap for anything but the most modest bends to force compression to the inside of the curve rather than stretching on the outside of the curve. You can't really put a backing strap on a turned spindle. And finally, it will bend at the thinnest points. If you think you are bending a modest radius curve, all the bend will be taken up in the thinner parts of the spindle, putting too much stress on those areas, that you also can't get a backing strap on.
While it can be done if you plan ahead, most likely your pre-turned part won't survive. If you do it, have some spares. Steam bending at first is a trial and error endeavor, and that is with S4S stock, a backing strap, the right species, the right moisture content, and effective steaming. If it is ash, red oak, white oak, hickory, elm, beech, hard maple, black locust, cherry or walnut, you have something to work with. Otherwise, probably not.