bending wood part 2 material & prep

[smitty10101]

What thickness is best and practicable for bending wood? 1/16? 1/32? something else?
How are you achieving that thickness?
Power machine? Hand tools?
The sequence of machining?

How tight of a radius/diameter can a novice reasonably expect to achieve?
How thin of stock to make a given radius?

What is your preferred material for your jigs? Plywood, mdf, osb, solid wood?

What trick/tips do you care to pass along??

[Herb Stoops]

Here is my take on this subject. Not to discourage anyone, just me,and my experience.
I wanted to bend some white oak 11/16" thick into an "S" shape for some legs for a coat tree.
I built a steam box from 4" diam PVC pipe,put caps on the ends,one removable. Added some roof gutter spikes at 1/3 of the way up from the bottom every 12", to support the wood off the bottom. I have a carpet steamer so I hooked that to the low end of the box. Also put a drain cock into the bottom at the low end. At the top end of the cap I put a BBQ thermometer , and a small hole to relieve the pressure. While the wood was steaming in 4' lengths ,approx. 45 minutes I made a jig to do a slight bend on both ends. The material was 5/8"X 2.5"W X 4' long but the "S" was about 18".
I maintained 220°F for 45min, and the PVC collapsed from the heat. I worked up a real sweat bending around the shallow curves and broke lengthwise one piece, and broke the jig on the second one, along with a long sliver off the side of the second.
To add to that a flat steam box.
Undaunted ,I went to the lumber yard and bought a sheet of 1/2" MDO plywood,(Medium Density Mylar Overlay), and made a new steam box. To make a long sad story short, same thing happened, except the steam box held up. So then I tried to bend some 1/4" thick oak strips 4' long a 3/4" wide , every dang one broke. So I ended up cutting them out of a wide plank on the bandsaw and problem solved.
I had read every Utube video I could find before I started and some of these guys were bending oak 2X6's around into circles like they were noodles!!
So this experience put it at the top of the list of things not to do just above Marquetry and Intarsia.
Herb

[Herb Stoops]

Here are some of the ideas for a steam box. I had more but can't find them, but will give an idea what to make.
Herb

[Stick486]

got ya covered...
is getting bent anything like bite me???
.

STEAM BENDING WOOD.pdf

STEAM BENDING 1.pdf

STEAM BENDING 2.pdf

[smitty10101]

@Herb

Did you try it with a metal band backing & thinner material?

[Herb Stoops]

No I didn't try a band, just a wooden"S"shaped form and clamps. The previous attempt was for the liner in a Saratoga Trunk I was relining for the DIL. I was using 1/4" thick X 2 1/2" wide redwood. Those I wrapped in towels and poured boiling water on them and let them set for 10 minutes adding more water as I waited. I had ends raised and a heavy weight in the middle. That worked I had to install them wet and let them dry inplace after I nailed the ends with a air nailer. I wouldn't do that again, too messy.
Another time I bent thin wood veneer in a loop for a padlock hasp and glued up about 10 layers, those I just did dry so I could glue them to hold them.
I think I can get along in life without trying bending again.
Herb

[kmealy]

Random drivel:

Most of the bending I've done is for Shaker oval boxes. I have a metal tray that I put water in and set it on a double burner hot plate. The wood goes in for about 15 minutes an is taken out and bent and nailed right away. The thickness varies from 1/16" for the smaller ones (#1) on up. It's been my understanding that the heat also plasticizes the lignin (but I could be wrong). They also say that air-dried bends better than kiln-dried. I've done both. For thinner stock, it is important that there is little grain run-out as this creates a natural weak spot. Also some species bend better than others. When a daughter graduated from Sycamore High School, I was going to make a bunch of Q/S sycamore boxes I had over 90% failure rate

For the boxes, the initial bending forms are 2x material. The cross point is marked, then it's taken off, nail the fingers, then I have plywood drying forms that go in the top and bottom. There are two holes in each for both to let out the moisture for a day and to put fingers in to remove it. The edges have a slight taper on them so they slide in the side pieces. The top band is then bent around the base and nailed, then slipped back on so the fingers and nail lines align.

A few years ago, I was making some chairs with a compound curve back slat ending up about 1/2" thick. I put pieces in the shaker box cooker, took them out, glued them up and put them in a bending form. When I pulled them out the next day, they were still dripping wet inside and the glue did nothing. I reduced the thickness of the laminations and just did a cold press with glue, and it worked fine (hard maple).

Most of the wood that I've done boxes in has been cherry, hard maple, ash, and red oak. I have few problems with any of them. If I do get a blow-out on a Shaker box, sometimes I can cut it in half and make a tray.

I built a steam box once out of 1x pine. It ended up warping and coming apart. If I ever do another, I'll do CDX. It was for repairs on barstools with a round seat wrapped in laminations that had broken apart. It was a pain.

The other thing I've heard but never used is to put on a metal strap to put the piece in compression on the inside and not tension on the outside of the bend.

[Cherryville Chuck]

I wanted to band some discs I made for lazy susan shelves. I wanted them to stick up about 1/2 to 3/4 of an inch so that stuff wouldn't fall off where it would be hard to get at. I clipped the fronts off the discs so I could make the discs bigger and still close the doors which also made banding the rounded part easier since I didn't have to worry about getting the lengths right, and the lengths would have to be perfect plus have tapered ends for the splice joints.

I didn't bother steaming and if you get the thickness of the strips right you shouldn't need to in most cases. They do need to have good grain. I tried about 1/4" thick in pine but that was too stiff and wound up around 1/8" thick or maybe a tad thicker. You have to experiment with each wood to find out where the limit is. I tried bending by hand to put a strap clamp on but I couldn't get the strips to bend uniformly and they broke. So I wound up having to make a set of curved cauls to match the curve of the discs and pull the strips round that way. The cauls also did a better job a mating the strips to the discs for the glue joint between them too. Going around a circle like that the cauls had to be made in segments and put on in order from back to front.

As the cauls went on I wound up having clamps crisscrossed in every direction and I also had to screw the cauls down to a backer board to keep the pressure on them from flipping them up. The end result was pretty good. Not perfect but good enough. Had I taken more time to properly fit the cauls to the discs It might have worked a little better but the job didn't require that level of fussiness.

Wood can just be heated too and that will also soften it up some, just not as much as steaming does. I've seen guys bending wood strips over a hot pipe. Both methods soften up the lignin in the wood cells and lignin is essentially a plastic. One of the organizations with government sponsorship here was experimenting years ago with extracting the lignin in wood and using it to make things like car fenders. Lee Valley's catalog can provide some insights into bending in the descriptions for some of the apparatus they sell.

BTW, the rule of thumb for steaming time I've always seen is 1 hour per inch of thickness of the wood.