Gluing finished surfaces

[Tom Porter]

Several months ago, during the lockdown, I decided to build a new bench. Because I didn't want to go get lumber for the top due to pandemic concerns, I had the bright idea to try layering up a bunch of hardwood flooring I had on hand. Maybe I should have run the boards through the table saw to skim off the finish but I didn't, figuring I'd sort out how to remove the finish from the flooring later. I glued them up, edge to edge, into panels narrow enough for my planer but subsequently decided the whole thing was a fool's errand and decided to not use them for the bench top. Removing the finish so the glue would adhere was not worth the time and effort with the equipment at my disposal, despite my desire to reuse materials rather than waste them.

But out of curiosity, I'm wondering what others might have done to glue up layers of finished hardwood flooring and whether there was an approach I hadn't thought of (which is usually the case).

[Prashun Patel]

I'd rough scrape them with a card scraper and maybe a jack plane (depending on the type of wood) before running them through a planer.

All the hw flooring I get is grooved on the underside, so my stuff would be so thin as to not justify the time and labor to reuse it. Also, if your flooring is random length, it'd complicate the glue up.

[Jamie Buxton]

I'd be cautious about running prefinished wood flooring through my planer. Some of the really durable floor finishes are that durable because they contain very finely powdered aluminum oxide. Aluminum oxide is what's on most sandpaper.

[Frank Pratt]

I'd be cautious about running prefinished wood flooring through my planer. Some of the really durable floor finishes are that durable because they contain very finely powdered aluminum oxide. Aluminum oxide is what's on most sandpaper.

Very true. Even running just a few feed through will completely dull a set of knives, unless you have carbide cutters.

I like to use every last bit of hardwood that finds it's way into my shop, but prefinished flooring just isn't worth the effort. Unfinished flooring can sometimes be useful, but mostly not.

[Brian Tymchak]

If you have a drum sander, several light passes with a heavy grit might do the trick, assuming the light passes keep the finish from gumming up the sand paper. But for all the reasons Prashan mentioned, IMHO, this would be a waste of time.

[Bernie Kopfer]

I think the OP has raised a marvelous question. How to glue together finished surfaces. Sometimes the best option of removing the finish is not possible/practical, so is there a glue or technique that will bond these surfaces together and how strong will the joint be. I’ve used epoxy on roughed up finished surfaces but in a non shear stress situations. Not a fun job, would like something better.

[Tom Bender]

So we're looking for a chemical that will melt and reactivate the finish and make it act as an adhesive. Acetone might be worth a test.

[Alan Lightstone]

I was thinking drum sander, then if not completely removed, epoxy.

How many layers of flooring were you planning on using? Seems like a ton, with thin wood flooring.

[Tom Porter]

It would have been 5 layers thick. As I said, it was during lockdown and I was in a "use what you have" state of mind. I had the time, the glue and the flooring. What I didn't have was the intelligence or foresight to see that it was an idea not worth the glue or the time.

[mreza Salav]

I won't expect it would be a worthwhile effort either but I would skip gluing them. Remove the tongue, put them on the edge side by side (so width of it becomes thickness of your bench top) and then riddle them with nails together from the face. Faster and skips spending other resource to remove the finish.

[Bruce Wrenn]

Titebond Melamine glue. That's what I use on prefinished plywood. Tried another brand with less than stellar results. Glue melamine boxes together with this stuff.

[Edwin Santos]

I might have tried clamping the hardwood strips into sandwiches and while clamped, drill and glue dowels in the stacks. Alternatively you could use screws as clamps and remove them later. Or use screws instead of dowels if you don't mind having metal in your wood.
Once the sandwiches are cured, run them through the planer on edge to clean up the edges. Now you have a whole bunch of narrow boards to use as you wish.
To make a bench top, edge glue them and use cauls to keep it all flat.

You could use the same procedure on the panels you've already glued up, and use the table saw to clean up the edges. If the hardwood flooring is grooved on one side, it shouldn't matter.

[johnny means]

Titebond Melamine glue. That's what I use on prefinished plywood. Tried another brand with less than stellar results. Glue melamine boxes together with this stuff.
Plus one. I use melamine glue on just about anything smooth or glossy.