Warp across grain when bending

[Phil Walsh]

I'm having problems with sides warping across the grain when bending. I'm using LMI's electric iron. Over the weekend I was trying to bend some quilted cherry, and it warped really bad. I tried not wetting it first, and that helped, but it was still unusable.

In the past I've had a minor problem with the edges curling up away from the bend, but not so bad it could not be sanded out. Is there a way to prevent or minimize this, before I invest in a bending machine?

Phil

[Alan Carruth]

Quilted wood is anywhere from skew to flat cut, and will warp in all sorts of interesting ways. So far I've had the best luck using Super Soft 2 with that stuff. A back strap is necessary as well.

[Phil Walsh]

Thanks Alan. I tried some SS2 on some quarter-sawn cherry, trying to make it easier to bend a cutaway. I couldn't see that it did much of anything. I'll give it a try on this anyway.

[Doug Shaker]

I cut my sides very thin, bend them roughly to shape, then laminate them in a mold with a layer of softwood. That allows me to use very wonky
(and beautiful) wood and still have a stable side.

[Michael Lewis]

I first bend sides over a half body form to approximate shape, then put them in the outside form to "true" them.

My approach to the rippled sides is to use a heating blanket and an outside form and metal slats. I place a metal slat in the form, then the wood, and next the blanket, and finally another metal slat. The idea is to heat the wood enough to soften and clamp the 'sandwich' of metal, wood, and blanket firmly against the inside surface of the form with C clamps. This makes the wood soft and forms it against a very smooth and even surface, totally eliminating the ripples.

This process gives the most 'perfect' side you are likely to find.

The expense of the heating blanket is small compared to the wasted wood you are likely to make.

[Phil Walsh]

Michael, that sounds like a great alternative to buying a whole machine. What kind of metal do you use? I got some 28 ga. steel to use as a backer plate as Alan suggested, and it did help quite a bit. Problem is when it bends it stays bent; makes it a little tough to use on the next bend, especially if it's a much different radius.

Alan, I tried SS2 on this wood, and it did help a lot.

[Barry Daniels]

You really owe it to yourself to invest in a couple of sheets of spring steel; somewhere around .012" thick. Returns to flat even from previous use for cutaway sides. It will rust so place layers of aluminum foil to separate the wet stuff from the steel.

[Michael Lewis]

Or, you can use stainless hard shim stock. It comes in 6" width from industrial suppliers (McMaster-Carr, MSC, etc.) in several thicknesses and lengths. I have .012" and .017", and use the heavier gauge for the outside surface against the form as it provides a fairly stiff surface to clamp your wood against. being stiffer than the lighter gauge it also resists 'telegraphing' irregularities like bumps and dips in the form. This stuff will take some set but mostly straightens out when released.

The real benefit with this system is the sides come out very flat across the bends and smooth along the side, which eliminates much of the sanding and scraping to get things flat, and consequently uneven thickness of the sides. This will help you step up a notch or two toward being a better craftsman because it helps save time (sanding etc.) and it makes for more even and better construction.

[Hugh Anderson]

Flashing is about .012.

[Barry Daniels]

Flashing is much softer than stainless or spring steel and is not as useful keeping the wood in check.

[Stephen Neal Saqui]

I found some smaller sheets of Titanium that were big enough to use in my cutaway bender. They blew me away! They almost had no memory after many uses and then just a subtle wave.
I'm now looking for some to use in the Fox bender. Does anyone have a source? Anyone tried it?

[Barry Daniels]

Titanium? Really? That stuff is insanely expensive, I thought.

[Stephen Neal Saqui]

I don't know! I got my sheets at a scrap metals place and didn't cost much. Judging from my experience with the cutaway bender I'd pay a goodly sum! I'd never have to deal with this stainless ever again!

[Doug Shaker]

It isn't necessarily insanely expensive. Less than a Brazilian back-and-side set, certainly. You would need to
know the thickness to get, though. The grade would be helpful, too.

The thinnest that these folks have:
http://www.onlinemetals.com/merchant.cf ... p_cat=1353
is two hundredths. I have no idea if that is too thick or just right.

[Stephen Neal Saqui]

Doug, Thank you very much!
I will do the homework. The pieces I have are covered in codes...may as well be in Sanskrit! But some metal guy will be able to read it. I'll post a thread here, just maybe someone is using titanium for bending already. I'll do that this evening.

[Michael Lewis]

I think you would want grade 5 titanium, as the grade 2 (annealed) is softer and malleable, which means it won't be springy and tough.

.02" is twenty thousandths, on the thick side but definitely useable if you watch out for the springy tendency when releasing it from under a cutaway side. Danger lurks, so one needs be careful.

It looks like a 12" X 36" piece could be split into two 6" X 36" slats, cost of material about $100. and I would think about how to cut that piece into two. Should last a lifetime.

[Barry Daniels]

I am not sure what advantage titanium would have over blue spring steel, other than the prestige factor.

[Stephen Neal Saqui]

I am not sure what advantage titanium would have over blue spring steel, other than the prestige factor.

Barry,
Prestige is nice for some but I've had good use with titanium and much better luck than with stainless.
Are you using blue spring steel in your bender? If so, what thickness is it? Does it develop memory? What is your experience using it? How stiff is it when you're taking the side out after bending? Where did you get it"
Thanks for the help.
Stephen

[Michael Lewis]

One benefit with stainless and titanium is it doesn't rust like spring steel can. Ferrous metals are reactive with some woods (walnut, oak, etc.) and can cause stains deep into the wood. The stainless is way cheaper than the titanium.

[Doug Shaker]

Here is Online Metals' page for full hard stainless shim stock.
https://www.onlinemetals.com/merchant.c ... p_cat=1175

It looks like for $60 you can get something to experiment with.

What thickness are your existing stainless strips, Michael?