Will I have any issues with the ends on my solid table top meeting at 45 degree angle

[Michael Yadfar]

I'm almost done building my coffee table, and I built the top about a month ago. The top has boards glued together making a solid slab, and a 4" boarder runs around that. On the edges, the boarder is glue sideways in the same way as the slab is glued together. On the ends on the table top, the boarder is screwed in by pocket screws since you can't glue to end grain, and I also glued anyway. The boarder meets on 45 degree angles on each side of the table. There probably isn't much I can do about it regardless, but I was curious if I would have issues with the corners pulling apart from expansion of table top. The table top is only 23" wide, so I don't see too much movement happening.

[Andrew Hughes]

Aww don't worry about silly stuff like that you'll be fine. But your table will probably push the miters open.Sorry for the bad news.

[Kevin Jenness]

Best keep it in a hermetically sealed chamber.

Considerations for further projects:

Species, grain orientation (quartersawn vs flatsawn), overall width of panel, expected range of moisture content. The expected movement can be easily found by using the timber movement calculator (Shrinkulator) at woodweb.com. Equilibrium moisture content is approximately 6% at 30% relative humidity and 10% at 55% RH.

This design can be built successfully with a veneered construction.

You can glue end grain. By itself a butt joint has little strength, but pocket screws plus glue with a reasonably narrow joint width results in a strong enough joint for cabinetmaking. Try breaking a glued pocket screwed butt joint after the glue has cured and the screws are removed and you will see what I mean. That will not save your table, though.

If your table is made of quartersawn mahogany in equilibrium with its surroundings and the RH swings are no more than 2% you will probably be ok. Flatsawn maple and 5% swings, not so much.

[Michael Yadfar]

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This isn't my table but it's basically what I did. The center is maple, and the boarder is walnut

[Dave Arnett]

I wouldn't abandon the project just yet.

I did something similar a couple years ago on some counter top.
I advised against it, but was overruled.
It's qtr-sawn red oak.

I did this...


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You might even add a few biscuits...couldn't hurt.

It's been a couple years now. So far, so good. (no guarantees)



edit: I misunderstood. Yeah, I think your miters will get pushed apart.

[glenn bradley]

Fatalistic statements (and well warranted) aside, the degree of problem will vary with the species and the variance in moisture in the air throughout the year. Most tables with this appearance come in the veneered particleboard versions where there is no movement concern or if a solid glue-up panel like yours is used, the table top is floating in the frame with room to move. Having a perpendicular assembly that is effectively glued solid is a general no-no at a certain scale. If the piece is for you, I would go with it (since, as you say, it is too late now) and see how things work out. If it fails you will have the chance to make another one and enjoy the learning process. If it is for someone else, I would re-make the top.

[Michael Yadfar]

It's not really so fatal at this point. All I have to do is cut off the ends, and it will be perfectly acceptable. Then I can just buy a bit more walnut and do a floating style running perpendicular. It's being kept in a house that's heated and cooled year round, so there aren't any rapid moisture changes. Also, what would happen? Would the whole table top fail, or would the corners of that frame just pull apart?

[Brian Tymchak]

It's not really so fatal at this point. All I have to do is cut off the ends, and it will be perfectly acceptable. Then I can just buy a bit more walnut and do a floating style running perpendicular. It's being kept in a house that's heated and cooled year round, so there aren't any rapid moisture changes. Also, what would happen? Would the whole table top fail, or would the corners of that frame just pull apart?

Assuming you just attached the borders to the table, this is the season with the lowest humidity levels here in the Midwest. The top is likely at its minimum width. I bet since you are nearer to the East Coast your humidity levels swing to greater extremes. With the pocket-screws, I'm not sure there will be enough "play" in the screw pockets to allow the top to expand. Maybe, but I'm not hopeful. This could lead to a split in the top with time. You might be able to add some play into the pockets that are more towards the edges of the table. Never tried to stretch a pocket screw hole out, but there might be a way. IMHO, the glue seam will certainly fail with time, possibly in the first year.

Edit: reread your first post more closely - I use a rule of thumb of 1/8" expansion per 12" of width (Kiln Dried) for design constraints and take the time of year into account to understand where the lumber is in its contraction/expansion cycle (a lesson I learned the hard way when building my workbench tops.. split top with boxes stuck in the middle during the summer..:() If you put a breadboard style of end on with some play in the attachment points, that should keep the top from splitting. That also avoids any miter joint opening up. However, for part of the year the top might expand out beyond the length of the bread boards.

[Michael Yadfar]

The pocket screws attach the table end to the edge of the border, the end border is not attached to the edge. Right now, the top is unfinished and not attached to the table. I have a few options that I feel I can do, either just finish the table and wait it out, maybe nothing will happen, or cut off the ends and find a new way to incorporate the same design. The top was the quickest part of the project, maybe took 1/4 of the building time, but is probably about $80-100, so I don't want to completely restart

[Kevin Jenness]

If the center panel expands the miters will open. If it contracts significantly, the pocket screws in the end borders may cause splits in the maple. Time will tell.

[Michael Yadfar]

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Here's what I'm working with just for reference

[Sam Murdoch]

Dave Arnett yours is a good system for your project ( I have done similar with bar tops) but not really relevant to the set up the OP has created.
His miters will inevitably open up or crack the top as others have suggested. A veneered ply or mdf substrate would accept a mitered border but not a center piece made up of solid wood. Michael - I'd be inclined to cut the perimeter boards off, apply new side pieces and bread board ends.

[John TenEyck]

Route a 1/4" slot through the top down the center panel, or one in each of those walnut strips, and the expansion/contraction will all happen towards the center of the panel. Otherwise, keep that top in a very well controlled environment or risk the wrath of Mother Nature.

John

[Michael Yadfar]

I think my best option is cutting and doing the breadboard ends. Considering the amount of hours that went into this, and the finish work to come, I would rather get this done right. I was considering the possibility of reusing the ends I cut off, but I'm still thinking of how I would hide the miter joints or work them into the design. I do have a short length of walnut in my basement though

[Dan Hahr]

Your only workable option is to cut the ends off and add new breadboards. I would do it soon before the top shrinks and splits the top down a glue line or weak section. You will need to make a tenon on the end and use a wider piece of walnut on the ends if you want to keep the same dimensions. It will end up looking better IMO.
Dan

[Brian Tymchak]

I think my best option is cutting and doing the breadboard ends. Considering the amount of hours that went into this, and the finish work to come, I would rather get this done right. I was considering the possibility of reusing the ends I cut off, but I'm still thinking of how I would hide the miter joints or work them into the design. I do have a short length of walnut in my basement though
The only way I can think of to keep mitered corners in the design is to create a frame and float the center panel in a groove (known as frame and panel construction). But this will likely create a small gap between the frame and panel during some part of the year. This can be a real crumb and dust catcher. Unfotunately, since solid wood expands and contracts, you have to always compromise in some fashion.

[Darrin Davis]

The mitered corners WILL open up or the inner part WILL split. Just depends on the time of the year. It will happen. Period!!! Especially if your mitered ends are glued or connected with screws with no play.

Generally speaking, wood expands or contracts approximately 1/16" either direction per foot of width. That's a total wood movement of 1/8" per foot and in your case close to 1/4" of movement.

I built a few table tops that were 24" x 24" out of red oak, maple, mahogany, and walnut to test out. All, without exception, varied in width by approximately a 1/4" at opposite times of the year. (they varied from 23 7/8" to 24 1/8" in width) That's why they say breadboard ends line up perfectly twice a year. This experiment with all the tops were done with my high school classes and measured each month and recorded. The kids were amazed how much they expanded or contracted.

Good Luck.

[Michael Yadfar]

I have no doubt now that I will do breadboard. I will have to research the technique, but it should work out. The ends I cut off can just be reused later for another project, so it's not really much of a waste.

[Sam Murdoch]

I have no doubt now that I will do breadboard. I will have to research the technique, but it should work out. The ends I cut off can just be reused later for another project, so it's not really much of a waste.


Congrats on your evolution. You'll make yourself a really sweet table :cool: