Steam Bending Question (Answered)

[Dave Richards]

http://farm8.staticflickr.com/7392/12586557324_cff425a770.jpg (http://www.flickr.com/photos/8294157@N08/12586557324/)

This is a piece designed by Josef Hoffman and made originally around 1906. The diamonds are bent pieces similar to those used in the familiar bentwood chairs by Thonet. If you were going to make a reproduction of this piece, would you bend the diamonds from square-sectioned stock and then make them round with a router or shaper? Or would you start with round stock? In the photos I've found of the original piece, the seam where the ends are joined isn't visible but I would guess a long scarf joint was used along one side.

[Bradley Gray]

The Thonet chairs were bent from already rounded stock so I would try that first, with several extras.

[Jamie Buxton]

I'd make them from rectangular stock. That way, if the ends don't quite match up, or the scarf joint doesn't quite line up when you unclamp it, you can nonchalantly belt-sand the thing flat, then do the round-overs.

[Chris Fournier]

Dave I would start to answer your question with a question, do you have dowel stock that is over long ready to bend?

[Jamie Buxton]

Are the diamonds round cross-section? I was reading them as rectangular cross-section, with roundovers.

[Dave Richards]

Chris, no. I don't currently have dowel stock that long. If I were to bend round stock, I would make it round. I'd probably split out pieces to avoid grain runout and round them over.

Jamie, the diamonds are round in section. Again, similar to the common bentwood chairs. I like your suggestion of being able to clean them up after bending and before rounding.

[Prashun Patel]

I'd bend the square stock. If you started with round stock, wouldn't you get compression/expansion around the curves? Wouldn't that alter (albeit slightly) the edge profile?

Also, might it be marginally easier to clamp the square stock properly in the form?

Also, I think you stand a better chance at an invisible joint if you roundover after.

I don't think it'd be that difficult to route by hand after formation.

[Dave Richards]

Prashun,

I think you're right about the compression in the corners deforming the section shape. Now that I think about it, that deformation is commonly seen in bentwood pieces so I expect Gary is correct that they bent round stock.

I'm with you on making it easier to clamp if left square and also easier to deal with the joint when there are flat faces available.

[Duane Meadows]

Is it possible to bend wood that sharply without some compression/expansion?

[Dave Richards]

Duane, I'm sure there would be some compression/expansion but like Prashun, I'm thinking it would be easier to deal with if the stock gets shaped to round after bending.

[Loren Woirhaye]

I would use square stock and use a backing strap. Consider doing the squares as 2 parts each, or even 4 corners. You'll spend a lot less time joining the pieces than you will getting a steam bending thing figured out to do each as one piece.

Can you post a larger picture of those?

I would entertain the idea that they could be sawn out as one piece.

[Dave Richards]

Sorry Loren, this (http://farm8.staticflickr.com/7392/12586557324_b726699f62_o.png) is the biggest image I've got.

[Robert LaPlaca]

Hey Dave, I would add this disclaimer that I have never steam bent myself, but I did research the topic... It seems as though the species of the wood and how it was dried (or not dried) determines how successful the outcome..

I have supplied a link to a free manual supplied by Lee Valley that outlines the entire process in pretty great detail, I don't believe that the link would be violating the TOS of this forum.. http://www.leevalley.com/us/wood/page.aspx?c=&p=45869&cat=1,45866,45867

Good luck

[Mac McQuinn]

IMO,This would be a interesting and possibly infuriating project. The actual material to be bent, thickness, spring back, distortion, expansion, etc all need to be kept in mind. There's a formula for how long to steam considering the thickness and even this can have varying results. It looks to be about a 100 degree bend. I would use the best material for bending and then do the rest of the project in the same material to match. There's a article in the new FWW with a few Arts & Crafts designs by Hoffman. In one of the designs you can just make out what appears to be fracturing lines on a bent piece. I'm sure age, humidity, finish all come into play here although it needs to be taking in to account. While I know it would not be designer correct, I would consider cutting the diamonds from flat stock with band/jig saw and round them with either a router, or by hand using a spoke shave. Not period correct although worth considering and would give you additional options for the materials needed.
Mac

[Jay Jolliffe]

Do a search for bendable wood & you'll be surprised what comes up. I remember an add in maybe Wooden Boat or FWW that you could buy dimensional wood that was bendable.

[Dave Richards]

Mac, none of those bends is tighter than 90 degrees. ;)

That bendable wood might indeed be an option. I remember that ad and I think an article in WoodenBoat.

Thanks for the suggestions all. We'll see what happens.

[lowell holmes]

The only steam bending I ever did was in a Windsor chair class. We used green red oak, made round with a draw knife and spoke shaves. The bending in that class was done after whittling and shaping was done. I wood was freshly split before shaping.

I would make a test piece to see how I wanted to proceed.

[william watts]

looking closely at the the bend on the right and the bend at the bottom on the left side there may be a butt joint there. The bent corners could all be separate pieces connected with a straight length of wood by an end grain dowel joint. The finish also appears to be darker in the corners perhaps to hide the end grain joint. Build the the bent pieces first, then build the rest to fit. I have never bent any wood, so no experience to speak from.

Bill

[Stephen Musial]

looking closely at the the bend on the right and the bend at the bottom on the left side there may be a butt joint there. The bent corners could all be separate pieces connected with a straight length of wood by an end grain dowel joint. The finish also appears to be darker in the corners perhaps to hide the end grain joint. Build the the bent pieces first, then build the rest to fit. I have never bent any wood, so no experience to speak from.

Bill

+1 but I'd guess that the pieces were bent with a 90 degree angle, put in a jig and trimmed and then all joined and clamped. From a production standpoint, it would be much easier to make 4 pieces with 90 degree corners and join them than 1 piece with 4 90s.

[nicholas mitchell]

Here's a thought that will probably be shot down with extreme prejudice but..........................how about instead of just copying this design, make it your own.. Make the diamonds from metal.

[Dave Richards]

William, I can guarantee to you that the diamonds in that picture have no butt joints whatsoever.

Stephen, I see your point however I think I'd be inclined to at least try it as a single piece.

Nicholas, I'm not going to shoot your eye out, er, shoot your idea down. :D Metal could be kind of cool.

Here's a detail view of a chair from the same series.
http://farm8.staticflickr.com/7404/12600874385_91953c7693.jpg (http://www.flickr.com/photos/8294157@N08/12600874385/)

It doesn't look like the diamond is made from more than one piece of wood to me.

[Loren Woirhaye]

The corners are thinned out. The wood is probably riven and bent green. That would make it easy.

One issue with steam bending dry hardwoods is the straight parts will tend to bulge out a little. It's not incorrectable, but do understand if you bend dry sawn wood rather than riven greenwood you'll have to go to considerably more fuss and probably have a big reject pile at the end. I steam bend wood seriously and the preparation is indeed tedious, but if it's done correctly results are predictably good.

[Dave Richards]

Thanks Loren. That's good info.

[Chris Fournier]

If I had dowel stock then I'd try the following:

Bend up two "U"s and then scarf them together to make the square. Tablesaw jig for the scarfing and another fixture for the glue up. I'd carefully match and align the dowel stock before bending and then put the "pairs" back together for a tidy grain match.

If you bend square stock it will compress and pucker at the 90s, this isn't a show stopper but you'd have to clean this up before shaping.

I could see myself attempting to bend the entire square in one go thinking that I could manipulate things to work out, it would require tons of trial and error.

[Dave Richards]

Thanks to all who replied. I've got plenty of info to go on now.