face gluing boards

Re: face gluing boards

Dick Coers

How many clamps do you have? If enough, just clamp. Not enough, use cauls to apply load between clamps.

Re: face gluing boards

Ellis Walentine

To add to Dick's reply, it's fair enough to discuss what constitutes enough clamps. The old rule of thumb I used to follow is to imagine the clamping pressure radiating outward from the clamp pads at 45 degrees in all directions. Using that assumption, you need enough clamps that you can space them at a distance apart such that the pressure areas overlap slightly, or at least intersect.

Dick mentioned cauls, which are just additional pieces of wood that increase the distance of the clamp pads to the glue line, thereby increasing the size of the area where the pressure is concentrated. This means you need fewer clamps to apply equal pressure to the same area. Keep in mind that clamping pressure is less per unit of area when it is distributed more widely by cauls. This means you need clamps that are strong enough to apply the recommended pressure per square inch to your glue line. I can't recall the specific recommendations for different glues, but if your surfaces are milled flat and can be brought into close contact -- barely visible is usually best -- you should be okay, regardless of the glue type.

You didn't mention how thick your boards are, but if they are, say, 3/4" thick x 7" wide, without cauls you would need clamps roughly every four to six square inches for 100% coverage. If you sandwich your boards between two 2x8s, you can do it with a clamp every six inches down the center of your lamination.

Ellis Walentine, Host

Re: face gluing boards

mark

Thank you both for the helpful replies. It was very helpful since i've never face glued boards this wide. 1 board is about 3/4 and the other is about 1/2, in order to plane it down to 4/4.

Ellis, this is off topic but I'm sure it probably has been discussed on here before but it was saddening to learn of American Worker's demise. I know it would have survived if all of you guys would have remained. You, Jim Cummins, Dave Sloan and the rest. So sad. Ever Since you started this message board not long after Readers Digest take over, I always would have loved to have met you. By the way, when American Woodworker magazine sent me a subscription request before RD's takeover, that inspired me to take up woodworking.....thanks to you guys!

Re: face gluing boards

Keith Newton

Mark, another option is to use epoxy for the glue, which does not require high pressure as long as the glue from both sides are making good contact.

I’ll be making some 5’ x 8’ x 2.25” doors soon and I’will need to glue up the stiles and rails. I may just use the vacuum bag for the clamp pressure, which will be 14 psi, which is a ton per sq foot.

It occurs to me ..

Derek Cohen (in Perth, Australia)

.. that this is a time for a reversed spring joint (just made this up - not tried it). In this case, create a one-shaving hollow at the sides of one board (hand plane works best). This will leave the centre one shaving high. Clamping the sides will act like a caul.

For boards up to 3" wide, all I have needed was flat surfaces and a rub joint.

Regards from Berlin

Derek

Balanced lamination

Dick Coers

When you have to remove 1/4" to make your final thickness, take it off the 3/4" board so you have two 1/2" boards glued together. When I do that, I'd remove approximately 1/8" off each face before laminating. It's a safety factor so you don't expose a wetter surface one one side if the wood has not been dried properly. I said approximately since you likely will want to surface after the lamination. You should also be concerned how you support that length of stock during glue up. If you don't support it on a flat surface, you will likely have a permanent issue with whatever curve you had during clamping.

Couple things

Ellis Walentine

I see. Your final piece wants to be surfaced to 1" and you're starting with two planed boards, roughly 3/4" and 1/2" thick. I suggest you make your final jointing and thicknessing passes after glue-up so your final result will be flat and of uniform thickness.

There's an interesting, and pretty academic, aspect of this lamination that involves moisture gradients in your laminates, and, as Dick suggested, whether or how much to remove from the thicker board in order to result in the most stress-free joint. If you just laminate the two pieces as is, and then take roughly 1/4" off the 3/4" board to bring it down to your 1" finish thickness, and the 3/4" board is drier on the outside than the inside, that final thicknessing pass will cause the lamination to cup. Then, as it acclimates, it might flatten out again -- or not. The movement may be irregular, or not. It may be affected by the orientation of the rings or the figure in the two individual boards. In short, it probably doesn't pay to overthink this. Assuming your boards are relatively dry and stable, I'd just glue them up and thickness them down.

As for your salute to American Woodworker magazine, thank you for the kind words. Everyone on that team really enjoyed what we were doing, and I think it came across. Our rapport with each other, our readers and our advertisers was pretty special. Most of us are still alive and well, some are still actively involved in woodworking journalism, and we still reminisce occasionally about the good old days at Rodale Press. Lotta memories there. I'm glad you enjoyed the mag and that it may have inspired you to get into woodworking. That counts a lot.

Cheers,

Ellis

AW magazine

David Yoho

As I'm sure I mentioned to you in the past, I always loved the Rodale Press days of the magazine. It was the best one going. Funny thing - I was just telling my son, who has just become interested in working with wood, that when I started out there were no YouTube videos or much help on the Internet. I had no one close to go to for answers or use as a mentor. I started, like many others, by watching Norm. AW magazine was the single source of many answers for me. As early online chat groups developed and then WoodCentral, I learned a ton of things that helped me grow as a woodworker. Now I can pass on that knowledge to my son,. which will be a great feeling of satisfaction.

American Woodworker

Bill Houghton, Sebastopol, CA

Another vote for the glory days of American Woodworker. I don't have space to keep many magazines, and I didn't have money back in the Rodale Press days for a subscription. But the couple of copies I have from then are keepers.

Re: face gluing boards

John McGaw

Sandbags or other weights?

Re: Balanced lamination

mark

Both boards have already been planed and have been in the shop for a few years. I said the boards would be 70" but will only be 60" which is a little different. I'm making three of them which will house raised panel boards.

Re: Couple things

mark

Yes, I plan to plane the 3/4 board once laminated. The 1/2 boards were planed on both sides about a year ago, so that is why I decided to use those boards. The boards will house raised panel boards for the foot board of a bed.

No question, I had no interest in woodworking at all until AW sent me the subscription request, and when I got my first issue, I was hooked..I went straight out and bought me a Craftsman Contractor table saw....and it was on. I was in my early 20's then. A bunch of new tools later and now I'm pushing 54...lol

Re: American Woodworker

mark

LOL, I think I still have all the ones I had. As long as I have the room, I will keep them.

45 degree "rule" is not useful guide

Bill Tindall, E.Tn.

clamping pressure radiating outward from the clamp pads at 45 degrees

How far the force of a clamp propagates depends on the stiffness of that being clamped. A clamp force F will fall off with distance from the clamp face according to some function that involves stiffness. This fact is easy to visualize. If you were clamping foam, the clamp force F would only be significant under the clamp pad. If clamping 2" thick steel the clamp force would spread for many inches or even feet.

The way to properly think of the clamps needed is to decide what clamping force per square inch is needed, total square inches to be clamped and from these values calculate the number of clamps needed. Distribute the clamps uniformly and rely on the stiffness of the wood to distribute clamping force more of less uniformly across the surface.

However:

If what is being clamped is limber, some sort of backing will be needed to distribute the clamp pressure.

A problem face gluing lumber is the response of the surface to the water from the glue. The boards are going to want to curl at the edges of the assembly. Hence, additional clamping along the edges is necessary to keep the assembly together.

Keeping the assembly together over its useful life could depend on the grain orientation of the opposing pieces. Keep in mind that radial response to moisture gain or loss is about 1/2 that of tangential grain.

Because of the problems with face glued assemblies they should be avoided.