Gluing after finishing - How strong is it?

[DaveD]

I'm making this big (10'W x 9'H) wall cabinet out of esentially 14 different sized boxes made out of veneered 3/4" plywood. They will have 1/4" veneered plywood backs. The whole thing will then get a face frame put on it.

My question has to do with completely finishing the individual panels for the boxes and then gluing it all together.

Do I have to (in general) mask off where the glue joints will be (to get a stronger joint) before I spray on the stain and 3 coats of poly? Or will the intergrity of the glue joint be sufficient that I can glue right on top of the finish.

Common sense tells me to mask off where I will be gluing, but thats over 200' of masking I'd rather not do if I don't have too.

All joints will also be fastened with narrow crown staples. The glue will be Titebond III unless someone sees a problem there.

All advice welcomed.

 

[Monty]

Do I have to (in general) mask off where the glue joints will be (to get a stronger joint) before I spray on the stain and 3 coats of poly?

I'm afraid so... :icon_thum

All joints will also be fastened with narrow crown staples. The glue will be Titebond III unless someone sees a problem there.

I would just use TB-I or it's generic equivalent. TB-III is too expensive, without any benefit for this application (unless I'm missing something).

 

[Monty]

Just wanted to add... if you were going to do McRabbetted™ joints, I suppose you could apply the finish without masking, then cut the McRabbets™.



But, you would run the risk of marring your finished surface with the machining. To get the most possible glue surface, though, you would still have to mask off a little of the mating piece.

 

[DaveO]

Yes definitely mask off the areas to be glued. I will attest to the fact that glue will not stick well to poly. I screwed up once and forgot to mask off an area and the glue barely held at all.
Dave

 

[Howard Acheson]

As said, any finish, except a water based or alcohol dye stain, will interfere with adhesion. Water based woodworking adhesives require virgin wood to effect a good joint. No wood glue will adhere to a film finish like shellac, lacquer or varnish.

 

[jeff...]

I would think if you want to finish then glue, mask the glue joints, so you won’t get finish on them. Glue really does need a porous surface to form a strong bond; bare dry wood is the ticket to success…

 

[DaveD]

Thanks folks. I'll be masking off the areas that require glue.

 

[junquecol]

You could sand off finnish in glue up areas. It is a simple process, and greately speeds up things. Recent issue of Fine Homebuilding has an article on doing this. ROO glue and Titebond Melamine glue will probably stick to areas coated with poly, but strength of joint will depend on bond of poly. Go by local Lowes and look at book/ magazine from FHB on tips. Article on cabinet making with prefinnished panels is in that too. It is MUCH EASIER to finnish panels on flat rather than in box.