# Glue Joint Failure



## winluck7 (May 7, 2008)

Hi I'm still a newbie in woodworking and looking for some advise on glue jointing at least 1 1/4" thick wood.

I already have a glue joint bit bought at mlcs and this solves my glue joint problems before but it's only good for up to 1 1/4" thickness. I'm wondering if glue jointing lets say a 1 1/2" thick will bring me again the same problem before if i just do it with my jointer.

I'm afraid with glue joint failures specially when it gets hot in here. Are there any glue joint bits in the market that can be used for at least 1 1/4" thick?


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## GeorgeC (Jul 30, 2008)

Glue is a pretty strong medium and it does not often come apart.

Just what kind of joints is it you want to make?

G


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## woodnthings (Jan 24, 2009)

*Glue joint failures*



winluck7 said:


> Hi I'm still a newbie in woodworking and looking for some advise on glue jointing at least 1 1/4" thick wood.
> 
> I already have a glue joint bit bought at mlcs and this solves my glue joint problems before but it's only good for up to 1 1/4" thickness. I'm wondering if glue jointing lets say a 1 1/2" thick will bring me again the same problem before if i just do it with my jointer.
> 
> I'm afraid with glue joint failures specially when it gets hot in here. Are there any glue joint bits in the market that can be used for at least 1 1/4" thick?


Most tests of quality wood glues like Woodworker Original, 2 and 3 result in the wood failure rather than glue separation. The splines, and profiles and bisquits are used more for alighment than for their structural properties. However, a spline running the same length and direction as the long grain, is stronger if made with "cross grain" stock, since a long grain will have no greater strength than the wood itself. But, I think this is more for peace of mind than any real structural advantage. Your stock at 1 1/2" is plenty stout and since you didn't state your application, it's had to predict the conditions of use here.:smile: bill


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## winluck7 (May 7, 2008)

woodnthings said:


> Most tests of quality wood glues like Woodworker Original, 2 and 3 result in the wood failure rather than glue separation. The splines, and profiles and bisquits are used more for alighment than for their structural properties. However, a spline running the same length and direction as the long grain, is stronger if made with "cross grain" stock, since a long grain will have no greater strength than the wood itself. But, I think this is more for peace of mind than any real structural advantage. Your stock at 1 1/2" is plenty stout and since you didn't state your application, it's had to predict the conditions of use here.:smile: bill


Thanks for the info's , actually the one that I'm going to glue joint will be used as bed rails and it will be my first try, my lumbers are short in width. 

without using my glue joint bit, a part separation happens when temperature exceeds a lot higher than room temp. as experienced from my previous work. This force me to buy a glue joint bit and fixes my problem but it's only limited up to 1 1/4 " stock


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## cabinetman (Jul 5, 2007)

Typically, "glue joint" router bits are recommended for use in router tables. For a larger stock with comparative machining for "glue joints", a shaper would be a better bet. You could still get a satisfactory joint with just glue and clamps with that much gluing surface. If more than that is thought necessary, you could still just use a slot cutter and a router for creating spline grooves.


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## KevinG (May 8, 2009)

What makes a "glue joint" different than just a plain old "butt joint", is that it increases surface area, i.e. more contact area. There is no magic locking joint, it's the glue that does all the work.

With stock as thick as you are using, I would just butt joint them together. I've done hundreds of butt joints on 3/4 material, and as long as I have applied glue correctly and clamped correctly, I have had no failures.


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## GeorgeC (Jul 30, 2008)

"without using my glue joint bit, a part separation happens when temperature exceeds a lot higher than room temp. as experienced from my previous work. This force me to buy a glue joint bit and fixes my problem but it's only limited up to 1 1/4 " stock "

Your bed will be in temperatures higher than room??????????

The people that are saying a but joint is good for 1 1/4" stock know what they are talking about.

You must be making some type of mistake if the joint is coming apart. Or else you are letting the temperatures get above 400 degree.

G


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## Webster (Mar 6, 2009)

Would you be gluing up teak? or something similar???


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## KevinG (May 8, 2009)

I used to run a high production finish line, and our curing ovens ran in the range of 200 degrees Fahrenheit. The only "glue" separation problems we ever had were starved joints. To prove it, every run we had with high "glue failures", were split open and 100% of the time the problem was the lack of glue, not the "high" temperature of the oven, nor the failure of the glue itself.

PS. All butt joinery were used in the construction of our solid panels.


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## winluck7 (May 7, 2008)

I live in a tropical country and the highest temperature as of this year was 37 degrees Celsius, I believe at this temperature all my lumbers would be dry for such a time, for those who are using digital moisture meter may i know what's the best moisture range of wood for gluing up? 

i don't have any moisture meter and i'm planning to buy one. Correct me if I'm wrong, I believe that too much dryness or wetness of wood contributes to the failure of a joint.


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## GeorgeC (Jul 30, 2008)

Just because the ambient temperature reaches 37 deg. celcius (98.6 deg farenheit) does not mean the wood is dry. Most tropical countries have a high humidity. The wood, if outside, is probably reasonable moist. If the wood is inside in an air conditioned environment than it is less damp. Your local tropical temperatures are about what we see in the Southeast in the United States.

Any reasonable range of moisture conditions in wood are not going to effect how well it maintains a glue joint. If you use a glue like Tightbond III even water is supposedly not going to be a problem.

G


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## KevinG (May 8, 2009)

If you are dealing with lumber that has a high moisture content, than glue joint failure is only the beginning of your headaches. As the wood dries out you will see splitting, cracking and your finish will be spotty at best. 

Even attempting to correct a glue failure related to moisture problems with a glue joint bit is not a satifactory resolution. If it is failing because of moisture, it will fail with a glue joint as well.


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## rrich (Jun 24, 2009)

From what you are describing, it sounds like clamps would be of more use than a glue joint router bit. Unless you are using a very "oily" wood.


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