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I've been making a pretty basic case from plywood and would like to apply some veneer. Unfortunately, one surface needs levelling out because the plywood was a tiny bit warped. I don't have pictures to hand but can upload some if needed.

My plan is to apply wood filler then sand it down... but maybe there's a better way? Thanks in advance.

EDIT: The warp is not huge (a couple of mm at the worst point) but it's present on the top surface, which butts up against the side. So, at the point where the warp is at it's worst, the side piece sits slightly proud. I could sand down the side piece. Sounds like that would be a more robust option, but perhaps less aesthetically pleasing.

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    How large is the piece of plywood? How much is it out of level? and how large is the area depression area? – Ashlar Sep 17 at 23:40
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    This might work... o-k-a-y.... but the type of filler you use (wood fillers come in many flavours), the veneer type and thickness, plus the glue you're planning to use, are all factors. This is both for now and for the long term. I wouldn't expect this to last in good condition for a long time, in case this is a factor. – Graphus Sep 18 at 7:33
  • Thanks so much for your comments! It's about a 2 mm out of level. I realise that I've not described the issue quite right so I'm going to make an edit now. – Eddie Sep 18 at 18:42
  • The depression area is probably about 200mm x 150mm and the piece of ply is 550mm x 220mm. – Eddie Sep 18 at 18:51
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    It's generally considered good form to up vote all answers that you found helpful, and to give a check-mark to the one you found most helpful. Self-answers are always acceptable, however, when they simply summarize what was in other answers, maybe not so much - if you're adding new or different info, then absolutely. – FreeMan Sep 24 at 14:20
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I've only ever done simple small veneers, but my research suggests that surface prep in terms of flatness is less important than cleanliness. All surfaces must be

  • Acclimatized
  • Dust free; really, really dust free
  • Free of oils, including finger grease

Your results will only be as good as your prep. Just make sure the surface is reasonably true.

(As an aside, note that plywood is a type of veneer, so you are actually adhering two veneers together, if that helps with your research.)

If you have to use filler, you will have to do research to figure out if it needs additional glue preparation. This goes for any surface, really. But with plywood in the home shop, the assumption is that you will be using contact cement and a roller. That is, I am assuming you do not have a hydraulic or vacuum press.

So, your prep work will be more about preparing the surfaces for gluing up with a high-solids contact cement. This may include not just sanding to true (but not necessarily smooth -- check to see if your glue wants surfaces rough for good adherence) but also meticulous dry and damp dust removal, and probably at least one wipe with denatured alcohol.

You can also get adhesive backed veneers if you just want that convenience.

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  • This is a good Answer, but I'm not sure it'll address the OP's needs given he's dealing with a warp. This suggest to me that the filler work will have to be extensive, and if so that's likely to be the main obstacle to a successful outcome. We'll see, assuming we get an update with the details requested/suggested. – Graphus Sep 18 at 17:33
  • Thanks for the tips, jdv! I really appreciate them and will re-read this once I'm ready to apply the veneer. – Eddie Sep 18 at 18:47
  • Depending on the warp, the veneer might just follow the curve, but we can't know for sure. – jdv Sep 18 at 20:43
  • I suspect that the veneer would follow the curve of the warp, were it not for the fact that the other part of the butt joint protrudes slightly. I.e. There would likely be a small gap under the veneer. – Eddie Sep 18 at 21:39
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That's going to be a lot of filler and it would have to be a filler that bonds with your veneering glue well, also sanding it perfectly level is going to be a challenge. It's hard to advise without seeing the piece, but I would try figuring how to replace a warped part, or if that's impossible then whether a construction could be modified so that warped plywood part is level, i.e. maybe adding a support or a stiffener, gluing a corner block, gluing it to the butting piece, etc.

There's a chance that a veneer might straighten the warped part if the part is thin. On thin panels it is recommended to glue a backer veneer to prevent warping, so maybe this could be used to your advantage - gluing a thicker backer or not gluing a backer at all, depending which way you want it to counter warp. This approach gives no guarantees of course.

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  • Thanks for your answer, eGlyph! Much appreciated. It's going to be hard to replace the warped part, unfortunately, and it's quite thick at 18mm. I'll try to get a decent picture of it tomorrow and upload that. – Eddie Sep 19 at 18:09
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My plan is to apply wood filler then sand it down... but maybe there's a better way?

Typical "plastic wood" type filler is good for filling nails holes and small dings, but not always great for filling large, flat areas the way, say, auto body filler is. To fill a broad, 2mm deep depression, you'd probably be better off with something that's very strong and stable with good adhesive qualities, like epoxy thickened with wood flour or other fibers, or auto body filler.

So, at the point where the warp is at it's worst, the side piece sits slightly proud. I could sand down the side piece. Sounds like that would be a more robust option, but perhaps less aesthetically pleasing.

If it's not too late, I think you'd be better off removing the top of the case and replacing it with plywood that's flat. It'll never be as easy to fix your project as it is now, before you add the veneer. As jdv explained, the key to a good veneer job is a good substrate

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  • Thank you Caleb! It would have been pretty hard to remove the warped piece, largely due to my poor decision making during construction :) – Eddie Oct 24 at 14:19
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thanks for all your thoughts and suggestions. In the end, partly because of the tools I had at my disposal, I just gambled on using a filler – in this case, Big Boy Body Filler.

Aside from the fact that the filler smells bad and creates horrible fine dust when being sanded, it went quite well.

My veneering skills are now the limiting factor.

side oneside two

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  • I know, it's a bit ropey, but this thing is my first attempt at woodwork in about 25 years :) – Eddie Oct 24 at 14:20
  • I think that with a little more patience and practice I'd have been able to get a good smooth and level surface so I'm going with this as the accepted answer. EDIT: it is actually quite level but I'm conscious that it looks a bit ugly in these photos so perhaps it's not up to the standards of others. – Eddie Nov 23 at 20:48

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