Gluing two sheets of 1/4" plywood together ?

[Brian Runau]

I need some 1/2" quartersawn oak plywood for a project. No one locally carries the 1/2". Can't use 3/4" or 1/4" for what I need and don't want to do a panel glue up etc... from wood. I was planning on gluing two sheets of 1/4" quartersawn together to get what I need. Plan is to rough cut them oversized and then glue them together and cut them to finished size after glue up.

My question is how much of the surface do I have to cover in glue for an effective glue up? Rather than covering one complete side in glue can I do 2"-3" around the perimeter and then a large number of wide swaths in the mid section and will this work effectively? Since plywood is so stable I did not expect a lot of movement and didn't want to go crazy covering the entire surface with glue.

Thanks.

Brian

[roger wiegand]

I expect you will have uneven bulging if you don't glue the whole surface. Cover it all with Titebond using a paint roller and then put the piece in a vacuum veneering bag to clamp it would be my approach. Titebond by the gallon is cheap.

[Ron Selzer]

I agree with Roger, don't think you will be happy with your method

[Curt Harms]

If Brian doesn't have a vacuum bag I'd think cauls would be adequate. Cauls can be as simple as 2 X 2s with a bit of a curve in them. Put the curve down and clamp the ends so there's pressure across the plywood. I wonder if you'd have to coat the entire surface, I'd think a good band around the edges and stripes of glue every few inches would do. Contact cement might work and wouldn't require clamping but you'd have to be careful to not have any bulges when you lay one piece on the other. Contact cement is not forgiving. The other thing with contact cement at least of the solvent based variety is you'd need GOOD ventilation.

[glenn bradley]

Full surface glue layer, flat reference surface, clamp with cauls or evenly distributed weight. You don't mention size but, I have laminated plywood to MDF for work surfaces using a roller to quickly distribute the glue and barbell plates for distributed weight clamping. Make one sheet to your final dimensions, laminate an oversized second sheet, use the first sheet as a template to flush the added sheet.

In this picture I have used a double row of screws to clamp the middle. These were removed after the glue set. I have since bought more weight plates at garage sales for pennies per pound and can work screw-free for show-both-sides lamination.

446198

This is larger scale but similar in operation to what you are after.

446197

446196

It sounds like yours is a 'show' requirement and the laminated 1/4" sheets should be stable to a reasonable dimension.

[Mark Gibney]

Glenn that's a Pec Blem 4" double square in your last photo and I claim my $5.

I have used just a Titebond "glue web" to marry two sheet of plywood in the past with no issues, but it was always for shop fixtures, not for clients.

[David L Morse]

In my experience it doesn't take much clamping. The veneer surface of the plywood always seems to be the weak point. It splits off easily.

When my wife had her business we would laminate 1mm ABS to full sheets of 1/4" plywood. We started with a sheet of OSB as a platen. Laid down a sheet of ply and coated with generic PVA using a paint roller. Laid down the ABS and rolled out any air bubbles, wetting the ABS at the same time. Repeat that for a batch of twenty or so then added another OSB platen on top, along with a few toolboxes and whatever weight was handy.

I periodically peeled an offcut to check adhesion. There was never less than 50% wood failure and no gaps more than about 1/2" bare ABS.

[Jim Becker]

Spread the glue evenly and use cauls to keep the assembly perfectly flat on a work surface while the glue cures. "Hit and miss" glue spreading isn't a good idea for this kind of thing. Glue is cheap, relatively speaking, so get it on there and spread it around evenly with a card, etc.

[Charlie Jones]

Cover the entire surface. You can place bricks or other weights evenly over the surface if you don’t have cauls.

[Brian Runau]

thanks to everyone, full glue surface it is. Brian

[andy bessette]

I would use WEST epoxy, coating both surfaces, and weighting it on my flat workbench using a sheet of 3/4" ply as a caul to spread the load evenly, as I have done in the past.

[roger wiegand]

I would use WEST epoxy, coating both surfaces, and weighting it on my flat workbench using a sheet of 3/4" ply as a caul to spread the load evenly, as I have done in the past.

What is the advantage of epoxy in this application? That wouldn't have occurred to me.

[Lee Schierer]

What is the advantage of epoxy in this application? That wouldn't have occurred to me.

Epoxy can take longer to set up giving you more working time for clamping/weighting.

[andy bessette]

What is the advantage of epoxy in this application? That wouldn't have occurred to me.

Epoxy has a long working time, as Lee mentioned, and does not rely on the evaporation of solvents or moisture, or the presence of atmospheric moisture to enable curing deep within the laminate.

[lowell holmes]

I would practice on scraps before the glue up.

[Bruce King]

Don’t use the fast set glue, it will start to glob up before you can get an even spread. Make sure to have plenty at the edges.

[glenn bradley]

Glenn that's a Pec Blem 4" double square in your last photo and I claim my $5.

I have used just a Titebond "glue web" to marry two sheet of plywood in the past with no issues, but it was always for shop fixtures, not for clients.

$5 to Mark for the win! :D

[Alan Lightstone]

Full surface glue layer, flat reference surface, clamp with cauls or evenly distributed weight. You don't mention size but, I have laminated plywood to MDF for work surfaces using a roller to quickly distribute the glue and barbell plates for distributed weight clamping. Make one sheet to your final dimensions, laminate an oversized second sheet, use the first sheet as a template to flush the added sheet.

I like Glenn's method. Plus you get your workout, so think of the time you save not going to the gym. :D

Personally, I think I'd use epoxy, or something like Ultra-CAT™ PPR Veneer Glue (a high-solid content, pre-catalyzed powdered resin veneer glue with an extra long open time) and put it in a vacuum bag over a good reference surface of MDF. That's how I've done it, but fortunately never with a full sheet of plywood. That will give you plenty of open time, then I keep it in the vacuum press overnight. Of course, you have to have the veneer press / vacuum / bags etc...

[johnny means]

Unless this part is going to be stressed in some way, you don't need much glue. I just run a bead around the perimeter and a couple of Xs to hold the center together. Less glue will require much less clamping force. Too much glue causes the glue to flow to areas of less pressure, leaving thick areas. This is even an issue with a vacuum press maiking 14 pounds on every square inch.

[Ole Anderson]

I would use water based contact cement on both surfaces and use some 4-6 mil poly as a slip sheet. Then roll the heck out of it with a J roller on a flat surface. If you can't vacuum bag with PVA glue.

[roger wiegand]

I did some lamination with (solvent-based) contact cement when I was first building out my first permanent shop ~30 years ago. It has now failed and delaminating and I'm having to re-make those tabletops and fixtures. (actually it failed more than decade ago and I've been slapping bandaids on it since then until I had time to re-make things). This is consistent with my observation of how long in general it takes for the Formica to fall off of old kitchen counters. So contact cement is fine for temporary things, or if you're old enough that it will outlast you. The joints in those same tables done with titebond are solid as a rock.

Is the water-based stuff a lot better than the old solvent-based adhesive? It sure stank.

[Kevin McCluney]

Do yourself a favor and buy an inexpensive brayer to spread the glue. Get one with a metal axle versus plastic as the plastic will wear out quickly when rolling a large surface.