Crotch veneer, stability, and layers

R

rkutner1

Member
Hi all,

I'm building two small side tables with 10" diameter, 1/2" thick tops, featuring crotch mahogany sunbursts inside a 1/2" frieze of ribbonstripe mahogany, a central shaded fan, and holly stringing, like these:

65177726-2903-47B7-BACD-7E2556867816_1_105_c.jpeg

These first tries warped like potato chips, likely due to insufficient cross banding.

For a second try, I've made a lumber core pine substrate and was thinking of veneering the back twice (at alternating right angles), the top once (at a right angle to the lumber core grain), and then proceed to hammer veneer with standard hide glue the top with (this time) backed crotch mahogany sunbursts and veneer backed frieze, adding the fans and stringing later.

Would the time delay between the second cross veneer on the bottom and building up the complex design on the top create more warping, or would it eventually all flatten out once finished? Would the extra backer banding on the sunbursts and frieze also create an imbalance that would lead to warping?

Alternately, I could build the crotch pattern with veneer tape, vacuum press it with OBG and a corresponding backer veneer, and add the backed frieze later. There would still be 2 veneer layers on the back, 3 on the front, so curious if this imbalance will lead to more warping.

Thanks all for your thoughts, I'm trying to conserve my expensive crotch veneer as I've already trashed a good bit of it on the first try.
Rob
 
You have to keep the faces equal so whatever you do on the front, do on the back minus the inlay and border. If you veneer one face and let it sit, it will move. I would vacuum bag it with unibond.
 
So maybe cross veneer each side twice, and instead of hammering the show face assemble the sunbursts (backed with another layer to prevent crazing) with tape and let the press do its thing, with another cross veneer on the back for good measure.

Then the frieze, stringing, and edge veneer with OBG and clamps if everything works out from there.
 
No need for extra cross band. Just make it equal both faces. Crotch on the front and back, pressed at the same time. Dont think I would back it either.
 
I've pressed crotch veneers right onto a veneered substrate before and had it craze within months. I think backing each piece is a best practice to prevent craze, esp given how thin it is (.020").

So a 1/2" core, with 3 backer veneers on the back and 4 on the front (two backers, two layers on each sunburst) would work I think. At this thickness the more layers perpendicular to each other the safer, methinxt.
 
3 on the back and 4 on the front is not equal, unless im not following your process. I suspect it will craze more with hide glue vs unibond.
 
Yes, I guess I'd have to add another backer to the back after pressing the face veneers. In this case perhaps 3 and 3 would be easier but still safe.

Regarding OBG vs Unibond, they both have water so what's the diff?
 
Unibond has no water. It is a rigid glue where hide glue will flex. Each glue has their place but I dont know of any professional veneer shop pressing panels with hide glue. I dont work with "traditional" methods all the time as I do this full time for $. I dont think you are gaining much backing such a small piece with hide glue. Its just an added step.
 
Hmm, ok. Do you foresee any issue with first vacuum pressing a layer on each side, then pressing another two layers on the back and the backed crotch to the front?
 
I do see an issue with it. First, If you decide to glue the face crotch pieces to another piece of veneer and then let it sit, pretty good chance it turns into a potato chip. Ask me how I know that.... There are ways to keep it from not moving but its a risk and I do everything to eliminate risk. If you start pressing only one face at a time to your core and then let it sit....it can move. So if you press one face, veneer the other side asap. The way I would do this- if the veneer is not flat, Id treat it with a softener. I use GF-20, not the water/glycerin glue mixture. To dry it, I would iron it. I would make a template of the wedge shape. I usually use 3/8 ply for patterns. I would cut the veneer on the table saw stacked. I have a dedicated sled for veneer work and I would climb cut it with a top caul that I press down on. I raise the blade up into the pack and by pulling it towards me, there is no tear out. I would leave the last piece out of the pack to make sure it all fits well. Tape the front and back side together. Id press it on a piece of mdf, plumaply, or your own lumber core or maybe platform ply with unibond. Thats a day or less in time. The stringing would be done with a dremel. The banding I would probably make(cut) myself to get it thicker than the face veneer. Id route the edge and glue that in. Many ways to "skin the cat" but that would be my approach.
 
Sorry I wasn't clear; I was going to press two layers on each side (two backers to the back, the backed crotch to the front) all at one go in the vacuum press. Sounds like I should go with Unibond vs OBG for rigidity, and I think rather than pine a hardwood core (like cherry) might do better.

I've backed the crotches already (with Unibond One) and kept them under weight and they seem ok so far, I'm just waiting for some veneer and my vacuum press to arrive in the mail later this week. I have some softener from veneersupplies.com if the crotches move on me...

If I assemble the crotches with tape on both sides, won't the tape interfere w/ the glue? And yes I was thinking the same with the stringing and banding.
 
The way you want to press seems fine. I dont think the core matters a whole lot but if I was making my own lumber core, pine would be the last choice. I just never use it as its way to soft. Ive also repaired way too many antique drawers to count where the drawer sides are all worn down at the bottom edge. The commercial lumber core that I was able to get- this is back in the late 90s- was poplar or basswood if I remember but it had a thick cross band on it. Whatever species, I would strive for quartersawn material. With your crotch already backed with unibond, if those move, I doubt you will be able to re flaten them but I dont have experience with it. When you tape the veneer, I tape the backside first with masking tape or painters tape. Flip it over and use veneer tape on the face, then remove the tape on the back side.
 
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