binding sandwich always warps

[Mike Ryan]

Hello,
I like to make my own binding.
I am planning on curly maple as the main binding with 1 black and 1 red fiber purfling strips at the body join of the binding.
\My problem lately is always getting bowing of the sandwich after gluing no matter how long I let it set up. It is 1/4 inch maple and 2 .020 fiber purfling strips.
I use LMI's new yellow blue, I have used titebond and other yellow glues often with the same result.
I can still use the bowed binding but can't plane it once it is glued.
I could put a strip of purfling on the top side of the binding sandwich to balance it out and maybe the bowing would be less???
I have not heard good things about using epoxy for this. I wonder about liquid hide glue??

[Alan Carruth]

Curious. I use mostly wood veneers for the side purfling lines, although I do use fiber one in a while. These days I glue up with Titebond 3 that I thin out to get a bit more closed time to get the go-bars on. I leave the piece in the deck for 24 hours, and have minimal problems with bowing or warping. I did find, when making layups for my rosettes that you have to give it plenty of time for the water to get out or the different shrinkage raters of the various woods will cause problems. AGain, in my shop, 24 hours has become the rule for that sort of thing.

[Bryan Bear]

I think we are talking about laying up a log with thin veneers (to become the side purfling)and a thicker stick (to become the binding) that will be sawn into binding strips after the clue dries, If we aren't then, ignore everything I'm about to type.

I have done this only a few times but have not had any signs of warping after the fact. I think (though may be totally off base) that clamping time and method are both important. Like Al, I use TB3 and allow plenty of time in the clamps. More than 24 hours, mostly because I don't get in the shop everyday. I also have them well clamped to a sub-straight not just to themselves. I use the edge of my bench and lay the glued up log on it then use a thick straight caul on top of that. As I am placing the clamps I imagine a triangle coming down from each clamp at 45 degrees providing clamping pressure. I try to place clamps so that the actual glue lines are 100% covered by at least one of these triangles. The thickness of the bench and caul spread that force out much further than just clamping the veneers to the stick. I feel like keeping it flat long enough for the water to work its way out and not having any spots that don't get clamped well are keys to success.

[Mike Ryan]

i use a sandwich with a 1x4 or so caul on each side of a 1/4" maple then .020 red and black fiber or wood. I have been having a hard time finding the dyed maple I want and I don't want to dye it.
I use 3 inch wide stock so 1/4" x 3 x 30", then .020 red x 3" then .020 black x 3". Both wide sides of the sandwich are covered by rigid cauls.
Maybe I am not leaving it in the clamps long enough. Funny, I am in the desert and I had better results up north with lower temperatures. Could do it in the house. The shop is upper 80's and the house is lower 80's.
Why the titebond 3 over other glues??? More heat resistant??

[Bryan Bear]

Yes TB3 will hold up better to the heat and steam of bending.

I'm wondering if being in the dessert might actually be hurting you. I'm just thinking out loud here but if the wood is really dry and you add all that glue it might have a larger net effect than on wood that is slightly higher moisture content. Leaving it clamped longer will still likely be the fix. . .

[Dan Smith]

I'm with Bryan on the glue introducing water into dry wood.
I've glued veneer using Titebond, only to have it crack when it dries.
As soon as the glue hits the veneer, it swells and curls up like a potato chip.

[Mike Ryan]

The dryness of the wood may not apply here.
I keep all my wood I am about to use for 1-3 weeks before using in a humidity controlled garage about 35-40% RH.
The wood is always about 8% when I use the wood.

[Todd Stock]

Not surprised that gluing purfling on one edge of a binding with waterbased glue will cause a warp - if you can retrain movement of the binding and purfs, that will help, or go to CA for the glue-up.

How to:

1. Jig is just 1/4" or 3/8" HDPE milled up as shown...a piece for the base 12" x 5.5"-6", a fence 12" x 2" or so, and a 12" x 2.5"-3" moving feather board milled up with a table saw. Make the feather board adjustable to handle different widths of binding and purflings. My jig is mounted on scrap ply that clamps into one of my repair vises, so elevated to a good height for detailed work.

2. Mill the binding .005" thinner than the purfs - this provides a .005 'lip' to run the micropipette application tip against when wicking in glue

3. As each section is glued up (and the fixture shown can handle as complicated a stack-up as you want), mark with pencil and slide it through the fixture to next section to be glued

4. Over time, CA will build up on the jig...knock it off with a chisel. if the sandwich gets stuck due to a little too much glue, use a spruce scrap with an wedge shaped end...things will pop right out

5. Clean any excess glue off with a razor blade scraper

The maple bindings shown prior to cleanup and prep for binding have a three piece purfling attached (BW-G-WB) and laid flat both before and after bending.

[Randy Roberts]

I've always laid mine up with 15minute epoxy using vacuum. No moisture, no warp. No problem separating when bending the cut off strips as long as they are taped together at a few spots when put in the bender. If there are separations, they take care of themselves when glued into the channel during binding.

Todd, I realy like your solution for doing up individual bindings. simple, quick, and well aligned.

[Todd Stock]

I don't tend to use the same binding/purf combo that often, so doing a sandwich does not make that much sense. If I did a run of identical guitars (in terms of binding/ purf), epoxy would be the way to go...no water and no worry about inks running or whether pure will hold on to the wood. ditto vacuum.

[Jason Rodgers]

Todd, these pictures are familiar, and it makes me glad to see you share them here with us!

[Todd Stock]

You would not believe the number of occasionally irate emails, texts, and Facebook notes I get on that same subject. FWIW, the shots are all new - the jig is what probably seems familiar

[Alan Carruth]

Again: I've used Titebond or T3 for this for many years, and have NEVER had enough warp to be a problem. The key is to keep things clamped until the water is all gone. Even with epoxy there can be some difference in shrinkage between different species/cuts of wood, and that will cause a bit of distortion with humidity changes, water or no.