Gluing technique

Re: Gluing technique

Jesse Cloud

Yup. You don't need to flood glue onto the wood. Even Franklin doesn't recommend that.

There was an article a few years ago, I think in Popular Woodworking, that tested the relative bonding strength of thin, medium, and heavy coats. Turned out you don't need more than a thin coating, but you definitely need it on both pieces of the joint.

When I am gluing veneer, I mark the substrate with pencil lines that pretty much cover the whole area, then spread glue with a roller. Anywhere I can't see the pencil line has too much.

Re: Gluing technique

Yonak

I, also, am interested in hearing the answer to these questions. Why clamp so tight ?

I think Mr. Tindall...

Joe in a Cleveland suburb

has written about this in the past in regards to squeeze out and clamp pressure. I think.

Here is one discussion

Joe in a Cleveland suburb

I found using a Google search on WC

http://www.woodcentral.com/woodworking/forum/archives_handtools.pl/bid/3001/md/read/id/477266

Because ??

Bill Howatt

Perhaps it's better to wipe excess to ensure you don't have to deal with a joint that fails later due to starvation.

Bill

Re: Gluing technique

Barry Irby

Bill has done a lot of research on this and knows more about it than most of us.

I have always been in the squeeze out crew. By having lots of squeeze out I am assured of 100% coverage. OTOH, recently I have gone toward the "just enough glue to wet the joint Crew". I put a tiny bead of glue down both edge surfaces and then smear it out with my finger to just barely wet the 100% edge of the board with the thinnest layer of glue I can achieve. Then I clamp the two pieces together and still get a tiny amount of squeeze out. Exactly what I want. Also does not take a huge amount of clamping pressure. Preparation is important. I lay the boards out side by side and assure myself the joint fits nicely. I look for the surfaces to be square and straight and match each other. If the joint is sprung or hollow very slightly it's good. I am looking for less than 1/100th or less.

I also joint one with the face out and one with the face in to compensate for any miss setting in the jointer fence.

The goal in joint gluing

Bill Tindall, E.Tn.

The goal- a thin a layer of glue between 100% of the wood surface, and the joint closed before water leaves the wet glue line so that optimum coalescing of the latex occurs. In the extreme, only three molecular layers of glue is necessary between the mating surfaces, but most don't machine their surfaces to that degree of flatness.

The problems in achieving this goal.

1. Surfaces are not prepared dead flat so some pressure is needed to mash surfaces together.

2. Excess glue must be applied to prevent the glue line from drying before the joint is closed.

3. Sufficient pressure is required to squeeze out excess glue.

Woodworkers are free to believe that Franklin publishes recommendations designed to increase glue usage, that furniture factories are too stupid to deviate from. Or, we are free to believe that Franklin publishes recommendations based on their research into how to best use their product.

What I believe- Any glue squeezed out is glue wasted. Any glue that doesn't squeeze out is glue that is doing something useful. The only way I know I applied enough to fulfill the needs of the joint is to add enough that some glue squeezes out. Interestingly, this is exactly the practice I see in furniture factories that make glued panels.

Re: Gluing technique

Keith Newton

Trying to go too thin with water soluble glue shortens the open time, and work time before initial grab. If you move it after the grab, isn't good.

I just did a quick look at youtube to see what methods people use to spread glue, and didn't find any that I thought were very efficient use of the time which starts when you apply the first few inches of glueline before you need to have the last clamp on.

Once about 25 years ago I was hosting a club meeting here at my shop, and somehow the subject came up about applying glue for edge gluing, and I recall asking how most were doing it. Some use flux brushes to spread the bead, others popsicle sticks. Then I did a demo of how I do it the simplest and quickest way I had figured out to get a perfect amount across the edge without much excess.

I like to have my bottom clamps already set up with the planks laying on them the way they will end up once glued. Then I stand the board on it's edge and hook my index finger over the edge so the first joint makes a wide V that carries the largest part of the bead being squeegeed along, with the glue bottle tip about an inch ahead as I move along. With a little practice, the glue will be a little thinner on both edges and heavier in the middle, but I can run down the length of a board as quickly as anyone could just laying the bead without spreading it.

The only thing extra that you need it a rag with a damp corner to clean up the finger. Give it a try, anybody can do it just by looking at what is coming out the back as you move along adjusting the amount of pressure and keeping the right amount of bead in the crook. Before long it will become as natural as breathing.

(Message Deleted by Poster)

Re: Gluing technique

Paul Leuba

That seems to me to be a very efficient and effective technique.

Thanks for posting it, Keith.

Paul in Hunt Valley, Md

Re: Gluing technique

Clint Searl

The forces that 99+% of properly mated joints will ever experience will have no practical adverse effect even if the joint is considerably starved.

I don't agree

Bill Tindall, E.Tn.

I was good friends, and a lumber customer, with the owner of a local factory that supplied glued up panels to furniture factories. I saw what he worried about and emulated these procedures in my work. I am willing to believe that the steps he took to manufacture panels glued as best they can be were important for the performance of those panels in furniture.

Can anyone ensure that their panels will not be exposed to large humidity cycles or temperature spikes, like setting in front of a window, during their service life? If not, do your best.

It is so trivial to get optimum joints that I am unsympathetic to anyone not striving for this quality.

Claim backed by Franklin data

Bill Tindall, E.Tn.

I did a test where I tried to "starve" a joint by clamping it to the maximum force I could muster in a full sized machinist vise. Testing revealed the joint was adequately "fed" . Subsequently, in correspondence with Franklin tech staff they said they have never been able to starve a joint by clamp pressure either. End of story as far as I am concerned.

It is so easy to do what is recommended why are we having a discussion that might encourage someone to do something different? If anyone claims to know more about gluing than Franklin they are suspect. Ditto for furniture factories gluing panels . But then some believe we didn't land on the moon.

Belt and suspenders

If, indeed . . .

Yonak

it's true that glue is stronger than the wood itself, is it necessary to clamp the boards as tight as one can get them or, is it as good, or better, to not clamp so tight and leave a little thickness of glue in the joint ?

Re: If, indeed . . .

AZ in Colorado Springs

Clamp it tightly. The glue contains a lot of water, so "leaving some thickness" of glue isn't going to work out when the water evaporates. That's why it's no good for filling gaps in joints.

I use a toothbrush to spread the glue after it's squeezed out of the bottle. A row of little"pinheads" of squeezeout is the target.

Two more glue questions for Bill and others

Barry Irby

I have heard something about 70% coverage for the surface. My dim recollection is that this is for veneer. Does this apply to edge to edge joints in panels? (I understand it does not mean the first 70 inches of a 100 inch joint has 100% coverage and the last 30 inches has none)

The second question is on jointing with a Jointer. I run my boards IN and OUT meaning I switch which face is against the fence to cancel out any error in the fence, but I have seen it argued the knives leave little scallops on the edge and you should clean them up with a handplane. If you run the boards fairly fast you do get scallops, but if you run the last pass slowly the edge seems very straight and free of scallops. Also, I suspect if you rub the joints left to right any remaining scallops will nest into each other. What say you?

What is the reluctance to clamp tight? .

Bill Tindall, E.Tn.

I don't understand this discussion. There seems to be some reluctance to clamp tight. Why? What is the down side? Clamp as tight as your clamps can muster without distortion of what is being clamped. There is no downside. Franklin recommends as high as 300 psi for maple.

As described, glue is about 60% water. leave a layer of glue between mating pieces and when the water evaporates what is left behind is foam- glue with 60% air. Foam not strong.

answers

Bill Tindall, E.Tn.

There must be a UTube somewhere of panel assembly in a furniture factory. I am willing to believe they know what they are doing. Trust that they have optimized the process. Be impressed with the clamping employed.

"I have heard something about 70% coverage for the surface." ...Where do these notions come from!?! What theory led to this recommendation? It boggles the mind.

"but I have seen it argued the knives leave little scallops on the edge and you should clean them up with a hand plane." Must be necessary for hot hide glue for this is the environment where one would find such foolishness. Franklin tech literature emphasizes the need for sharp knives and proper feed rate but I have never seen a hand plane in a furniture factory panel assembly line.

Proper gluing is not hard-3 rules

Bill Tindall, E.Tn.

In fact it is probably the easiest operation in woodworking.

1.Apply sufficient glue to wet both mating surfaces

2.Get joint assembled before any surface drying occurs

3. Apply sufficient clamp pressure to bring mating surfaces together and squeeze out all excess glue

Many in the beginning ensure 1 and 2 by applying more glue than needed. With experience an optimum will be found. But be wary of point 2 in the effort to optimize technique.

Agree

Bill Tindall, E.Tn.

Belt and suspenders...and I would add, applied to well fit trousers.

Agree and disagree both...

John in NM

No need to worry about scalloped edges. Feed rate and sharp knives prevent them. Although I like handplanes myself, I always chuckle at those who feel the need to invent reasons that they are essential - they are not essential, just another tool that has some advantages to go along with its disadvantages. All tools and methods have both.

Factories, however, are not the be all and end all of quality. They are bulk manufacturers who may well have different goals than you or I. I have zero doubt that they have optimized the time vs quality equation, because time does equal money for them. I may want to take a little more time and achieve a little higher quality product - time is not money to a hobbyist, so our equation is not the same as theirs.

In theory, there is no reason why the average factory could not maximize quality while minimizing time, so from a theoretical point of view looking at factory methods can be very beneficial - but I think skepticism is always required because the individual builder tends to have a different goal than the factory. The factory owner or manager is probably not going to worry too much if he finds out their joints will last 50 years as opposed to 200 or more.

Re: Two more glue questions for Bill and others

Jesse Cloud

I am deeply skeptical about a 70% coverage rule for veneer. I guess it assumes that the dry spots will be wetted by pressure from the platen...

Sounds like a guaranteed way to get bubbles in your veneered panel.

I was taught that every bit of the substrate needs glue and before you apply the veneer to inspect it at different angles to look for dry spots.

Reality

Clint Searl

Re edge joining: since the result will be a panel, more or less, that'll never be under destructive duress, it's silly to obsess over 100% coverage and 1000psi. The objective is better directed to perfecting the dry fit with stable material.