laminated bending springback

Good question. With a 1/4” thickness you will have quite a bit of springback. It’s hard to say how much.
With 1/8” you would have a lot less. Closer to zero.

I would be prepared to make more than one to find out what works. Make your mold tight to start so that
you could take material off if it’s too tight.

-- Gary, East TX -- The longest journey begins with a single step.

Thanks Gary…I’ll blog what happens when I try.
I’m hoping by pre-bending I’ll eliminate some springback. I know of a harpsichord builder who bends the full 3/4” as one piece, but I’m not that ambitious.

Looks like I’ll be going back to the mill a couple more times before I get it right, but maybe I’ll get lucky.

-- Jon

I saw an episode of How It’s Made on the Discovery channel a few weeks ago. They showed clips of the construction process of building a Steinway Piano. The part where they did the lamination bend was fascinating. They applied glue to all the boards, and made a stack of them. Then about eight men lifted the whole dripping mess, and walked it over to the mold. They locked one end in place, and then marched in step around to the other side. When everything was in place they applied all the clamps, and tightened everything up.

I didn’t catch the type of glue that they used, but noticed that no one was wearing a resperator.

-- Scott, San Diego

”I saw an episode of How It’s Made on the Discovery channel a few weeks ago”

I’ll have to check that out…I’ve got a ton of ‘em recorded on the DVR, but didn’t see that one. I love that show! It’s a good place to get ideas, and some of the processes manufacturers use are unreal.

-- Jon

I seached Discovery’s websit, but didn’t find it in their episode listing. I did another Google search on “Steinway Piano TV Episode” and got the following link to a show called “Made in America.” I think that this might be the show that I saw.

http://www.tv.com/john-ratzenbergers-made-in-america/steinway/episode/377048/summary.html

I have no idea which channel I was watching.

-- Scott, San Diego

Hello Jon, You will want to use a Urea glue like Unibond 800 for this type of lamination. I also would recommend you use 1/8” thickness. 1/4” will spring back. The more laminations one uses, the more exacting the piece will come out of the mold. If you look at my Projects under the kitchen cabinet file you will see some curves I did that are around 7” to 7 1/2” wide curves sitting on a form. You will see that they have very little spring back. I resawed these 1/16” thick in order to get a virtually no spring finished curve. I used special 1/8” bending ply in the core with two 1/16 thick pieces on each side. I will try to post some photos of how tight this ply bends later.
John

-- Oldworld, Fair Oaks, Ca

Thinner is better to prevent springback.

-- Maplewood, MN

Thanks for the tips everyone…I will for sure go thinner. The best I will be able to do is to make my 3/4 inch lamination out of 4 pieces instead of 3. This will not be quite 1/8”, but better than 1/4”. I only have 4 pieces to work with on the bent piece…long story, but can’t make any more right now.

I drew out my full scale pattern tonight, and it’s not that tight of a bend. Hopefuly it won’t be too big of a deal.

I’ve have made quite a few bent parts in the past…did 6 cathedral windows, but I was not worried about 500 lbs of string tension pulling on the windows :)

-- Jon