Laminating Boards Into Blocks.

[Steve Garrison]

A lot of my sculptural woodwork starts off by gluing up thicker blocks of wood from walnut, cherry, and/or maple. I use a 6" jointer to flatten the faces and sometimes follow up with sanding on a plate of glass with 100 grit before gluing just to make sure the joint surfaces are perfectly flat. If I glue boards up face to face (original Titebond) they still somehow manage to get small gaps in the joint and also have a tendency to slip around as I tighten the clamps. The blocks are not very large, maybe 4 or 5 board feet at the most. How do most woodworkers handle this?

[Joe Jensen]

There are a few more things to consider when gluing up like this.
1) If the board is flat, but the thickness is not consistent, it will tend to slide when you clamp.
2) Some clamp types have more play, and when tightened they move the boards. I used to use pipe clamps I had these issues when clamping. I now use Bessey K body clamps and it's less of an issue

[glenn bradley]

If they were not for carving, or if you can deal with them being in there "somewhere", I use small brads pounded into one surface and then snipped off with side cutters. This leaves small "pins" that keep the pieces I am laminating from slipping around.

[Angie Orfanedes]

Some old timers (like me) shake a few grains of regular table salt on each surface before clamping. The roughness of the salt will hold the wood from slipping too much. Even doing it that way, you are better off to cut your pieces oversize and trim the glued up assembly after it has cured.

Regarding the gaps, you just have to screw those clamps tight - use scrap wood on each side, so you can really clamp those pieces tight without worrying about damage to the faces. Yes, there are some that say you can starve a joint of glue this way - but that has never been a problem for me. There are so many microscopic hills and valleys for glue to hide in - especially when using 100 grit - that glue starvation is not likely to happen.

[Warren E. Johnson]

Another possible explanation for the gaps is that when you apply glue to one surface of the board you are adding water. That water will cause the board to expand a bit and perhaps warp. Uniform clamping presure is necessary to solve this problem. When face gluing I have sometimes found that a light spray of water on the unglued face will minimize the warpage.

[Walter Plummer]

[QUOTE=Steve Garrison;1231378] If I glue boards up face to face (original Titebond) they still somehow manage to get small gaps in the joint and also have a tendency to slip around as I tighten the clamps.

Not to hijack, but how come glue is slippery and grease is sticky?:rolleyes:

[Tony Bilello]

Several things will make your boards slip. One of them is too much glue and another is that the boards are not an even thickness all of the way around and another is using cheap clamps and also gluing too many boards at one time and you lose control. If boards faces are not parallel to eachother, you will need a planer. If you are using too much glue, well, you can control that. Cheap clamps not pulling perfectly at 90*? You can watch how they are moving before final tightening and apply clamps opposite eachother as you go along. Gluing too many boards at once? Only you will know that.

As for the gaps, have you ever checked with a straight edge to see if you are joining the faces flat? No ripples from the joiner? Maybe you should be using a planer also?

[Steve Garrison]

I like that idea of adding a few grains of salt to help prevent slipping. The blocks get cut up on the bandsaw afterwards and I doubt that it would hurt the blade.

I have suspected that the moisture in the glue is the cause of gaps from warping. Thicker boards don't warp like thinner pieces. If the blank is small enough I use a hydraulic press i bought recently instead of regular clamps. Thanks for the help!

[Bill Arnold]

Using cauls will help with consistent clamping pressure across a glue-up. A caul with a slightly curved side toward the glue-up works best to distribute the pressure more equally.

Another thing I've used even for flat glue-ups is my vacuum pressing system. With this, I get dead even pressure across the glue-up whether it's curved or flat.

[Steve Garrison]

Yes, I also use a planer after the jointer - gluing up tapered pieces would just be asking for trouble. I glue the boards up in pairs - let dry then pair them up and so on.

I do check the flatness with a straight edge and correct the problem if any light shows through. I scribble a pencil line all over the surface and sand it off with the 100 grit on a glass plate. Any graphite left will show where the low spots are.

[Tony Bilello]

It is possible as well as likely that when gluing up in pairs, the pairs are not perfectly flat for whatever reason. The minute 'out of flatness' of the two pair would account for the small gaps because the stress of bending 2 double thick sections together would be more than the clamps are capable of doing and more than the wood and glue could handle. This couls also account for the excessive slipping if the two pairs were mated on a convex to convex position. Or........I'm all wet and am completely wrong, which gets us back to the excessive glue thing. A good glue joint only requires a 1/1000th of an inch thickness or so and more likely less than that.

[Steve Garrison]

After discussing this with you guys I think the gaps formed from warping from the moisture in the glue. Each pair of blocks have the next joint surface flattened by sanding on the glass plate just before being glued together. Either my clamps were not strong enough or I didn't use enough of them - and the warping occurs. The hydraulic press is far stronger than any clamps I have and I get better results using it. Some of my old 3/4" pipe clamps are bent from tightening them down so much trying to keep gaps from forming.

I use enough glue to easily spread completely over the joint surface. There might be a few small drips, but mostly I get a uniform row of beads along the edge of the joint squeezing out. The roughness left from sanding with 100 grit - or sometimes 80 grit I think is sufficient to retain enough glue in the joint. Thanks!