Gluing Baltic Birch that's pre-finished (from drawers)

[Doug Hobkirk]

How much finish should I remove before I can get a good glue joint between Baltic Birch and a maple board?

The ply veneer might be maple, but more likely it's birch.
The plywood is .45" thick with 9 plys, the outer 2 veneer plys are about .020 to .025" thick.
The area to be glued is the first 6" of a 6x22 board. Ideally, it'd be great to remove the finish from just the part to be glued (to save me needing to re-finish).
I have a thickness planer.
I have an excellent 6" ROS and a RIDGID oscillating sander.
I have extra plywood, so I can experiment... So DO IT! I used the ROS with 80 grit...


How deep? Do I just go deep enough that it "feels" like unfinished wood? I want a good glue joint.

PS - Sometimes asking a question like this forces me to dig into the details enough that I answer my own question. I think I came close here, but the forum's collective wisdom is too great to ignore.

"Put a finish on the maple board, leave the birch ply as is, and epoxy them together." by The Marine West Devotee
"Just sand until the finish is slightly scratched." by Don't Work Too Hard
"Pay Mathias Wendel to send you the rolling laptop desk you're trying to build. Forget this DIY stuff!" by I've read ALL your posts!



Thanks. And Cheers. (I always smile a little when blokes sign off with cheers, so this is my first time. Or would I be encroaching on "nationality issues"?) Smilingly...

[Tim Bueler]

I've had good luck using polyurethane adhesives, depends on how much stress will be put on the joint. Scuff the finish with course grit to give the glue someplace to bite.

[Edwin Santos]

How much finish should I remove before I can get a good glue joint between Baltic Birch and a maple board?

The ply veneer might be maple, but more likely it's birch.
The plywood is .45" thick with 9 plys, the outer 2 veneer plys are about .020 to .025" thick.
The area to be glued is the first 6" of a 6x22 board. Ideally, it'd be great to remove the finish from just the part to be glued (to save me needing to re-finish).
I have a thickness planer.
I have an excellent 6" ROS and a RIDGID oscillating sander.
I have extra plywood, so I can experiment... So DO IT! I used the ROS with 80 grit...


How deep? Do I just go deep enough that it "feels" like unfinished wood? I want a good glue joint.

Dear Wood Loon,
Could you share a little more about what you're trying to build and the design that's requiring gluing to the finished face of the BB?
Is it a corner joint we're talking about? Or are you trying to face glue to achieve a greater thickness?
The reason I ask is because I'd like to visualize whether a dowel, biscuit, domino(floating tenon), dado or rabbet joint would meet your needs.
Edwin

[Jamie Buxton]

I trust titebond wood glue and it’s equivalents from competitors. It wants bare wood. Sand off the pre-finish. If is like the stuff I get, the film is only a couple thousandths thick: 80 grit on your ROS will take it right off. You’ll likely see a color or sheen difference when you go through the finish.

Clamp a board to form a dam, to keep the ROS off the the Prefinish you want to keep.

[Jim Becker]

I agree with Jamie...remove the finish at the joint and use appropriate glue. (and other reinforcement if indicated) I recently worked with this material for some kitchen cabinets and made a few custom sanding blocks that had fences so I could use them to sand off the area for the carcass joints just shy of "the line" so that the TB-III could do its thing nicely while I benefitted from the nice pre-finished cabinet interior space and avoiding spraying into a box. (which is a thankless task, IMHO)

[Rick Potter]

If you are talking about glueing the corners of drawers, with table saw type glue joints, I simply used a wooden sanding block, cut a rabbet on one edge, cut a 1/2" wide strip of sticky back sandpaper, and stuck it on the rabbet.

The rabbet was cut deep enough that it also acted like a guide/fence, and a few strokes on the end of the boards gives a nice neat 1/2" wide sanded surface to glue to.

I also used melamine glue, to make sure.

Worked good on my 68 drawer kitchen.

PS: Recently attended a talk on glue by Tite Bond reps. I asked if melamine glue worked on prefinished ply. They said it did.

[Doug Hobkirk]

I've had good luck using polyurethane adhesives, depends on how much stress will be put on the joint. Scuff the finish with course grit to give the glue someplace to bite.
I don't have and have rarely used poly.


Dear Wood Loon,
Could you share a little more about what you're trying to build and the design that's requiring gluing to the finished face of the BB?
Is it a corner joint we're talking about? Or are you trying to face glue to achieve a greater thickness?
The reason I ask is because I'd like to visualize whether a dowel, biscuit, domino(floating tenon), dado or rabbet joint would meet your needs.
Edwin
I am building a rolling laptop desk with two sliding vertical pieces of 1/2" ply and a 1" maple arm that's 5" wide. I plan to partially "half lap" the joint by cutting 1/2" into the maple. Since the PVA glue bond is so strong ("stronger than the wood itself"), I don't expect I'd need to reinforce it. It will be a 5x5 surface of raw maple mating to a 5x5 surface of the plywood. The design is by a nutcase I love, Mathias Wendel, and his choice for this joint is a freaking dual huge long tenon (cut with a Pantarouter). See at 4:45 in his video (https://www.youtube.com/watch?v=JowgzxJR-xc).


I trust titebond wood glue and it’s equivalents from competitors. It wants bare wood. Sand off the pre-finish. If is like the stuff I get, the film is only a couple thousandths thick: 80 grit on your ROS will take it right off. You’ll likely see a color or sheen difference when you go through the finish.
Clamp a board to form a dam, to keep the ROS off the the Prefinish you want to keep.
Good suggestion on the dam. Better than the blue tape I'd planned.


I agree with Jamie...remove the finish at the joint and use appropriate glue. (and other reinforcement if indicated) I recently worked with this material for some kitchen cabinets and made a few custom sanding blocks that had fences so I could use them to sand off the area for the carcass joints just shy of "the line" so that the TB-III could do its thing nicely while I benefitted from the nice pre-finished cabinet interior space and avoiding spraying into a box. (which is a thankless task, IMHO)

Thanks, all. I wanted to be sure and now I am.