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.

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.