# steam bending .....spring back



## KurtaKalbach (Jun 3, 2013)

Was just wondering if anyone could tell me if there is a way to calculate the amount of "spring back" you can encounter when steam bending wood? I would really appreciate it.


----------



## nailbanger2 (Oct 17, 2009)

If there's one person on here that would know, that would be Loren. I'll guess at 10%, but don't know how you would measure that out. I'll be watching this thread for the answer.


----------



## Loren (May 30, 2008)

No. It varies from piece to piece. More pronounced bends
spring back less than very shallow bends because there's
more damage to the cells on the inside of the bend 
occurring. It doesn't vary a great deal. It's generally
manageable if you plan for small variations. You'll learn
from experience. Play with it.

A recent 40 degree bend in 5/8" material sprung back to
around 35 degrees. U-shaped chair seats spring back
but can be squeezed to the intended shape with the
ends mortised into the front legs.

You won't get identical parts steam bending and if you
leave steam bent parts "waving" like long rockers on 
a rocking chair, they are going to move around. If part
movement is restricted by joinery to other parts, it's
possible to make a piece incorporating steam bent
parts look like the parts match.

In industrial steam bending they may have it figured
out how to get the parts to closer spring-back 
tolerances than I have managed. Still, you'll almost
always see steam bent part movement restricted by
joinery and the parts may actually be a little more 
flexible after steam bending than before.


----------



## NoThanks (Mar 19, 2014)

I would imagine different species, different sizes of timber, would all make a difference. 
I doubt there is any one answer. 
Trial and error of what your doing would be the best method.
I think shipwright is the person I would ask.
I think he's on vacation at the moment though.


----------



## EPJartisan (Nov 4, 2009)

it also depends on the moisture content for some species of wood. if the lignin is already too dry it means it will not be as flexible when steamed… it will bend, but will give a bit more spring back and some small cracking.


----------



## runswithscissors (Nov 8, 2012)

A way to get a finished bend just right is to over bend it by a significant amount. Carefully unbend it by heating the bend with a heat gun while coaxing it to relax a little. No steam necessary.


----------



## KurtaKalbach (Jun 3, 2013)

Thanks to all who responded. I sure do appreciate all of you who are so willing to share your knowledge with the rest of us. Thanks again…. time to make some steam…


----------



## bigblockyeti (Sep 9, 2013)

I've practiced a little determine the feasibility of such construction for a couple different projects I have in mind and I'm finding what's already be posted. It's variable, and even when you do your best to remove as many of the variables as possible, it's still far from a sure thing.


----------



## fishcad (Mar 23, 2012)

I'm working on my first steam bending project. Actually my first bending of any kind. I am attempting to make a curve with a 13" inside diameter out of three 1/4" thick pieces of cherry. My first attempt was with kiln dried wood. After learning that was a no-go I tried again with air dried wood. I steamed the parts for 20 minutes and they seemed to conform to the jig without much trouble. I had a total of 10 clamps and left them clamped for two days. As the photo shows, they straightened out a LOT when I removed the clamps. Any thoughts? Longer steaming? Longer clamping? Wood still too dry?


----------



## bigblockyeti (Sep 9, 2013)

How wide are the pieces you've cut to steam? Did you clamp all three together or were they individual efforts?


----------



## fishcad (Mar 23, 2012)

The pieces are 1/4" thick and 1" wide. I clamped them as a group. The final piece (I hope to make 6 of these) will be these three glued together to make a piece 3/4" x 1". I based the 20 minute steam time on information I have found saying 45-60 minutes for pieces 1" thick. However, I have also read that cherry is not as good for bending as many other woods. Unfortunately I have to match some existing cabinets.


----------



## Earlextech (Jan 13, 2011)

fishcad - everything is fine. Now that they're dry, glue them up and clamp them to the form again. Once the glue dries you won't be able to take the bend out of them.


----------



## benchbuilder (Sep 10, 2011)

For bending woods that dont steam well, i do a glue lam method. I have built several steaming systems and done a far amount of bending but as evryone else has said its not a given everytime. But the glue lam is as close as i can come to getting like parts.. i use a wood steaming system i designed about 12 yrs ago and works well, but the wood is so unpredictable from one to another that i just use the glue lam jig i built. Not much help here but thought you might try the glue lam idea.. good luck with your project.


----------



## bigblockyeti (Sep 9, 2013)

+1 to the glue lam method, that's what I was thinking about when asking you if you had all three clamped together after steaming. You might have to cut your stock a bit thinner than 1/4" depending on what radius you're trying to achieve, but the spring back is far less and more predictable after a little experimentation.


----------



## benchbuilder (Sep 10, 2011)

Yes thats a good point bigblock, i forgot to say cutting the stock thiner is better. If its a long easy arch the thicker is ok but with about all bends the thiner the stock the easierit is to bend and less spring back..


----------



## fishcad (Mar 23, 2012)

Thanks everyone for your help. I glued them up and had less than 1/4" springback when removed from the jig. I will try the next one with thinner layers. Now a related question. I've read that some use wax on their jigs to prevent the glue sticking to the jig. I used packing tape which protected the jig, but most of it came of with the part. I would rather avoid replacing the tape each time. What are your thoughts on wax on the jig? Is there a particular wax I should use?

BTW: I just noticed that my original post said it was a 13" diameter. It's a 13" radius.


----------

