Longest cross-grain glue joint?

[Bennett Ostroff]

I'm working on some prototypes for twenty award displays I'll be making. This is 3/4" kiln dried walnut and all the pieces are being cut by a CNC for precision assembly. The only joint where the grain direction doesn't match is the circled joint which is just under 7". I used Titebond no-run no-drip glue. I called Titebond and they said their glues do have a small amount of flex and that a 7" joint should probably be okay. These displays will be in a modern office building, so refrigerated air year round, and a very dry climate (Denver).

I'm wondering if you all think a glue a joint this size with opposing grain directions is safe. I know I could just glue a couple inches in the middle but I don't want gaps at the ends. I suspect the hypotenuse joint should be fine even though it's not quite parallel grain directions. I know glued M&Ts are also opposing grain, but usually not this long. Is there a more flexible adhesive that would still be very strong? Thanks in advance!

[Mel Fulks]

I see no problem. Stable wood that is kiln dried. Span is short. I think Titebond will be fine.

[Doug Dawson]

I'm working on some prototypes for twenty award displays I'll be making. This is 3/4" kiln dried walnut and all the pieces are being cut by a CNC for precision assembly. The only joint where the grain direction doesn't match is the circled joint which is just under 7". I used Titebond no-run no-drip glue. I called Titebond and they said their glues do have a small amount of flex and that a 7" joint should probably be okay. These displays will be in a modern office building, so refrigerated air year round, and a very dry climate (Denver).

I'm wondering if you all think a glue a joint this size with opposing grain directions is safe. I know I could just glue a couple inches in the middle but I don't want gaps at the ends. I suspect the hypotenuse joint should be fine even though it's not quite parallel grain directions. I know glued M&Ts are also opposing grain, but usually not this long. Is there a more flexible adhesive that would still be very strong? Thanks in advance!

I would suggest a pair of floating M&T's on each side, glued at the front, slightly undersized and pinned at the rear. Here's that excuse you needed to buy a Domino. Heh, when you have a Domino, everything looks like a floating M&T.

Or you could use pocket screws, but that's not very romantic, not very romantic at all. (Good for building jigs that you might repurpose.) Elongate the rear screw guide.

[William Young]

According to a chart on line, flat sawn walnut should move (worst case) just a hair more than 1/64" over 7". IMO you should be OK. If you want to be extra safe, you could glue a spline into the side piece then insert the spline into a groove in the end of the top piece dry and peg it from below through elongated holed in the spline (like a breadboard end).

An alternative would be to make the triangular sides as frames with floating panels.

[Doug Dawson]

According to a chart on line, flat sawn walnut should move (worst case) just a hair more than 1/64" over 7". IMO you should be OK. If you want to be extra safe, you could glue a spline into the side piece then insert the spline into a groove in the end of the top piece dry and peg it from below through elongated holed in the spline (like a breadboard end).

An alternative would be to make the triangular sides as frames with floating panels.

Using the charts from "The Encyclopedia of Wood", dead-tree edition, the potential movement is as much as 1/8", but probably closer to 1/16", which is enough to be concerned about.

If the piece is constructed under conditions very close to where it will be used, and those conditions are always tightly maintained, this will be less relevant. That's how Norm would think about it. :^)

[Mark Bolton]

People will argue tooth and nail but it's not uncommon to see entire high end stair assemblies with 12 inch and wider cross grain nosings applied all day long and they last through and through. We have pushed super wide rails on furniture style vanities out to well past 12" with a cope and stick joint and never had a failure.

My gut feeling is 16-18 inches is where your going to be losing money. 12" and under would be safe zone.

[Bradley Gray]

As long as the wood you are using is used to your low humidity you will be fine. I am always afraid to send furniture to your part of the country because of the low RH. Wood in my world rebounds to 10% no matter what I dry it to.

[Richard Coers]

Not safe. Glue joint isn't the problem, it's the wood that will give. The sides will split, or they will shove the front away from the top. Can't fool with Mother Nature.

[Dan Friedrichs]

You'll be fine in Denver. I built a coffee table with breadboard ends, there, and after a few years of watching it not ever move, thought, "Well that was a lot of work for nothing". Then I moved to Minnesota and the table field grew 1/4" in a few weeks. Then I understood.

You, on the other hand, should enjoy the blissful life of never having a concern about wood movement...