Replies

1. 
   johnhardy | Aug 30, 2005 12:56am | #1

   Given that the bubinga is 1/4" thick, you're really veneering the top, although the veneer is very thick. I haven't done this, but everything I've ever read says that you veneer both sides to prevent stresses. I'm not sure what is equivalent to bubinga in terms of expansion properties, but I would think a less dear wood would work just fine.

   Another thought is to take your 1/4" bubinga down to 1/8". That wouldn't solve the veneer problem on the back, but it would create veneer that is probably more stable in terms of expansion. You could simply run it through the planer to remove half of the thickness. Or, you could glue it up as is and then run the whole table top through a wide belt sander to bring down the veneer thickness.

   John

1. 
   matthew1 | Aug 30, 2005 03:50am | #4

   Do you think that 1/4" plywood wouldl work underneath in addition to sanding the top down, or will I have to go through the same process for the underside

1. 
   johnhardy | Aug 30, 2005 09:58am | #8

   You need real wood veneer underneath, not 1/4" plywood. As others have said, the veneer you are putting on should be much thinner than 1/4". To simplify things, what I'd do is glue 1/4" pieces to top and bottom and then sand down to something slightly less than 1/8" (something like 3/32" or 1/16"). Sand down both top and bottom so that they are the same thickness. To me, it's just easier to sand down something that is thick and stable as opposed to running this stuff through a wide belt sander before you do the glueup.

   By the way, I know of several furniture makers who use MDF for the core of what you are about to do. It's very flat and the glueup would be very easy. But remember to glue to both top and bottom, and in my opinion you should do both at the same time. Otherwise when the piece you put on dries it'll make a large saucer of the MDF.

   John

2. 
   sapwood | Aug 30, 2005 01:21am | #2

   You are indeed actually veneering the table if you glue 1/4" boards onto plywood or any other stable medium. And, if you persist in this, you will get the opportunity to do it again, because the "veneer" will certainly fail. I know this from direct experience. I made a mahogany table with 1/8" veneer (shop sawn) and all of it warped and pulled the mdf core loose. The glue didn't fail but the mdf did. I would presume that with
   1/4" the stresses could delaminate the plywood. I suggest that you resaw again and aim for 3/32 max. Oh, and you must veneer both sides of the tabletop.

1. 
   matthew1 | Aug 30, 2005 02:07am | #3

   Do you think that 1/4" plywood on the bottom in addition to sanding more thickness off would be enough?

   Edited 8/29/2005 8:48 pm ET by matthew1

2. 
   matthew1 | Aug 30, 2005 03:51am | #5

   What type of wood should I use for the bottom. Could I possibly use plywood?

1. 
   sapwood | Aug 30, 2005 05:13am | #6

   When veneering over a stable substrate such as plywood, one must build a balanced structure. This means that whatever you use as a top veneer layer you must also use on the bottom. Ideally you would use the same species and definately the same thickness. Both top and bottom layers are glued on using the same kind of glue. (Don't use contact cement.) This structure balances stresses top and bottom so that there will be no warpage. Any deviation from this protocol can mean trouble. You must fully understand the problems involved before you push the envelope, so to speak. Now, as I said in my prior post, if you use "veneer" as thick as 1/8" you are asking for trouble no matter how many layers of plywood are underneath and no matter what goes on the bottom of the built-up structure. 1/8" and certainly 1/4" is simply too thick. These boards will want to act as lumber and not as veneer. It will want to expand and contract with the seasons and will either tear itself or the ply or the glue bond apart. Veneer (real veneer, 3/32" or thinner) can be constrained by the glue because the stresses involved are not great. It's the same principal that makes plywood work as a structure. You never see commercially made plywood with 1/4" outer veneers, so why would you think that you can make such a thing successfully. I would advise you to resaw your boards again to get thin veneers. This is possible using a standard bandsaw. (There have been many discussions in this forum about resawing.) Edge band the plywood inner core and apply the veneer. Actually, mdf will give you a better product, it's smoother and flatter then ply.

3. 
   mudman | Aug 30, 2005 06:02am | #7

   Unfortunately I too think that you have a bad idea there. To do what you are trying to do you need veneer thickness, as in well under 1/8". Those 1/4" pieces will behave maore like wood, than veneer. When they expand or contract (notice I said "when" and not "if") you will have splitting and all sorts of issues. In order to salvage them you will have to take them to a shop with a wide belt sander to take them down to veneer thickness. I think that you would be better off if bought some veneer.

   As the others stated what you do to the top of the table you must also do the the bottom.

   Mike

4. 
   Malcolm | Aug 30, 2005 12:44pm | #9

   The advice about your bad decision is correct. If (as it appears) you've already glued your 1/4 bubinga to a base, you're amost certainly in trouble. No point in trying to balance it with equivalent wood on the bottom - just doubles your trouble! Taking it down to less than 2mm will minimise the risk (but you may find that technically demanding), and then counter-veneering on the back will help keep it flat.

   If it were me (or if you'd given this problem to me to solve) I'd get the bubinga off the substrate - even if it means machining or chiselling off the ply! Then you could try to resaw down to 2 or 3mm and make up a new sandwich with veneer on both sides of a substrate like MDF or a quality ply.

   My feeling is that you will also find this a challenge, but it'll be a learning experience!

   Good luck 

   http://www.macpherson.co.nz