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Adam

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If you want to veneer one side of plywood only, what thickness of plywood would you need to stop it "pulling" - e.g. curving. Does the thickness of the veneer have any effect? What happens if you veneer really "chunky" veneer of say 5mm plus onto plywood of 12mm? Would you need to back it with an equivalent amount?

Adam
 

GCR

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Adam

I have not veneered that many panels, but my experience has been that whenever I have tried to get away with one side only, the panel cups. I have had problems with sawn veneer and can only conclude that two things seem to cause problems: Firstly the veneer expands across the grain when water based glue is applied and this inevitably causes problems. Secondly the ply or base panel is rendered "out of balance" by the veneer and thus cups over time. (Even birch ply is rarely flat, unlike "red" ply which is usually stout-heart construction and thus balanced for grain).

Bob
 

Chris Knight

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Adam,

I have nearly always balanced my veneered stuff, except for smallish test panels and it is the received wisdom to do this.

Paul Richardson, former editor of F&C uses hammer veneering a lot and says that if you leave a veneered panel face down on newspaper to dry then it stays flat. (See page 76 in Furniture Making Techniques, if you have the book - publ. by F&C) I tried it once on a small panel and it was OK. (Hammer veneered stuff can take a long while to dry completely. I left it for at least a week).

I have no experience with very thick veneer., other than gluing a couple of similarly thick pieces of ply together and these stay flat after I have used my vacuum press on them.

I suspect a lot of the potential curvature comes from the drying out of wet veneer so if you used the iron-on PVA method, you might be better off. (I would never use contact cement myself).
 

Adam

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I have left things single sided - but always on 18mm thick backing. I'm thinking thick veneer is more likely to cup than thin veneer as it can exert a stronger force?

Adam
 

Chris Knight

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Adam,

Sorry, I just don't know. I think one could argue that a thick veneer will cup less as well but only an experiment will show.

If you have enough of the stuff, you could use 6mm ply and sandwich the lot I suppose.

Give us a clue - what are you making? and where do you get such thick veneer?
 

Adam

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waterhead37":1hhng3a4 said:
Adam,

Sorry, I just don't know. I think one could argue that a thick veneer will cup less as well but only an experiment will show.

If you have enough of the stuff, you could use 6mm ply and sandwich the lot I suppose.

Give us a clue - what are you making? and where do you get such thick veneer?
Thick veneer comes from offcuts - so I could plane it down to something thinner I guess, and I'm making a box - which was only going to be plywood, but the competition has made me think about learning something new. So veneering (something I've only done a couple of times) and turning the sides. - you'll have to wait to see if it works!. Not very descriptive I know, but I haven't worked out if its possible yet, nor if my lathe is big enough!

Adam
 

The Restorer

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I've found that thin veneers tend to cup more than thick. I think this is due to my practise of damping down the veneer and putting it between MDF under weight to flatten it prior to laying. This, combined with hammer veneered application will cup veneer thats not countered. I think that the thicker stuff (1.5mm and up) doesn't absorb so much moisture and so doesn't move so much.
Of course it can be useful to have the veneer stretched pretty well when hammering to bring bowed door panels back flat again in restoration :) .
There are plenty of pieces of furniture around with pine substrates and veneers on only one side that have hardly cupped at all. :?
I agree with Waterhead37 that Paul Richardsons book is very good as is Veneering by Ian Hosker.
 

jasonB

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I've made a box in a similar way but used 0.5mm veneer on the inside as the core was 6mm MDF and ended up with 3mm of oak on the outside after planing, no problems with cupping. All the oak came from an offcut of 5x2 about 7" long





If you are using this method glue all the bandsawn veneer, planed side down to a long strip of ply/MDF then it can be fed through the thicknesser as one long board which is easier than feeding lots of short lengths especially if you get snipe.

Jason
 

Chris Knight

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Jason,

That is a really beautiful little box. (You should enter it for the competition!)

Re the tip on planing the thin veneer, how do you get it off the MDF when you have planed it?
 

tim

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Re the tip on planing the thin veneer, how do you get it off the MDF when you have planed it?
My question as well.

I love the depth of grain that you have got - what did you finish it with?

Cheers

Tim

Whose hoping that Jason didn't take any WIP photos thereby rendering it unsuitable as a competition entry :shock: :lol:
 

jasonB

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I don't . The box sides are made up as a sandwich of MDF with commercial veneer one side and the bandsawn on on the other. Once planed they are cut to size, Joined etc as a single piece of solid wood would be.

Whats the competition :?: The one in F&C :?:

Jason
 

Frank D.

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Boy Jason, that's a really nice box. It looks a lot like my humidor :wink: :


I used thick veneer (1/8", 3mm or so) on Spanish cedar, only one side but it did cup a little within the first few days (I had a delay and couldn't assemble right away). One-sided veneer is usually a no-no but for a humidor it is apparently OK (humidity is constant on the inside). I just wanted to say that when you glue veneer to a stable substrate like MDF or birch ply, the veneer should be as thin as possible or else it can move with seasonal changes in humidity and split or crack. If you really want to use thick veneer it's safer to use a stable solid-wood substrate like mahogany or Spanish cedar, and orient the grain in the asme direction so they can move together.
Frank D.
 

Chris Knight

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Jason,

What a wonderful notion! I feel as thick as a brick for not thinking of it but even so I haven't seen it done before.

I was referring to the competition here on UKW for man-made materials projects.
 

Chris Knight

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Frank,

Gawd! That's gorgeous! I shall have to practice my box making skills when I get a chance.

At present you and Jason rule the box makers' roost!
 

jasonB

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Your all safe, I made the box a while ago and there are no WIP pics but I could nip out to the workshop and make another :lol:

I was really pleased with the fit of the lid, you can feel the slight suction as you lift it off then impress people even more by replacing it back to front and still get the same fit :D Another thing to remember is that if you get the veneer in the right order the grain pattern will run round three of the four corners. The finish is danish oil then chesnut wax on the outside, celulose sanding sealer & wax inside to keep the maple light.

Frank, funny you should say its like your humidor, I got the construction method from a FWW article about making a Humidor, it's on their site if anyone is interested. I left out the cedar as I'm not a smoker :wink:

http://www.taunton.com/finewoodworking/pages/w00069.asp

There are a couple more of my boxes in this album which I like more than the oak one.

http://photobucket.com/albums/v156/jaso ... 20turning/

Jason
 
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