[OP]
Contributor
So I’m going to join the legs to the table top with dowels and glue. The board that is going to be joined is 40” long, and 2” wide.
was thinking 2 rows, staggered and 6” spacing. A shit load of dowels, but want it to be strong.
Any one see an issue othe than the meticulous layout I will have to do!
ABB0913D-C41C-4FDB-ABD7-7C0554F18393.jpg
Hopefully the top is wider than 2" wide. If you don't allow that top to expand and contract seasonally you are going to have problems and likely a failure in the form of a cracked top. Place dowels along the centerline but use figure 8 fasteners where you planned to place the other dowels.
[OP]
Contributor
The top is 2 thick. The board I am joinin to the top is 2” wide, it will be perpendicular to the top.
Top seems stable. It went a whole
Year glued up, no splitting, expanding etc. cold dry winter to hot humid summers.
Yes, but it wasn't being restrained by the 2" wide cross pieces you plan to attach it to.Originally Posted by Jim Riseborough
Lee Schierer
USNA '71
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Moderator
Um...wood movement. You can fasten secure in the middle, but you do not want to glue out toward the edges of the table or you're going to have a hot mess with seasonal changes in dimensions for that cross-grain joint. Screws/bolts in slotted holes in the cross member are typical for this task.
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The most expensive tool is the one you buy "cheaply" and often...
Contributor
Unless the RH was dead constant, it was expanding/contracting the whole time; you just didn't notice. Go put a tape across the width. Chances are it's not the same exact width as when you made it.
John
Contributor
I think it will be fine if you are really attaching just the legs. It looks like two screws per leg. Leave one hole a little big or slotted to allow movement. If you mean the legs AND the apron. It will split the top in one or more locations in a few seasons.
You say the top did not move in a year. How often and how accurate did you measure it? The human eye will notice a difference of 1/1000 inch in a flat surface like a table top. Were you measuring to that level of accuracy using correct temperature correction for your scale, gloves etc.Climate in shop, storage and end use location?
Bill D.
Moderator
Now I'm confused....I took this as attaching the leg assemblies to the table top, not the legs to the leg assemblies...'Hopefully, the OP will clarify.
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The most expensive tool is the one you buy "cheaply" and often...
[OP]
Contributor
Its the top of the leg assembly to the top.
I didnt measure it while it sat.
Its going to be in the house, and its a conditioned space, RH will be constant for the most part.
The boards didnt open up and joints, nor did they expand at the ends differently.
I will build in some expansion somehow.
Contributor
There would be no reason to expect a glued up panel of boards to split if they aren't constrained. They were free to expand/contract.
Unless you have some pretty special HVAC the RH is going to change quite a lot over the year. Best to plan and build for it.
John
Moderator
Seasonal wood movement is real no matter how well the home environment may seem to be. So do take care to allow for the top to expand and contract because it will.
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The most expensive tool is the one you buy "cheaply" and often...
Contributor
I was pretty much being sarcastic but I would like to know where does the RH not change?
Contributor
Outer space. But back here on plant earth it certainly changes. My house has central AC but in the Summer the RH can easily range from 70% when I'm not using it to as low as 40% when it's running hard. In the Winter it will go even lower unless I turn on the humidifier, and I do because I had some veneer seams split one Winter when it got down to 30%. A 40" wide table top made of plain sawn black walnut made when the lumber was at 8% MC (45% RH) will grow by 0.5" if it comes to equilibrium at 70% RH, and shrink by 0.22" if it comes to equilibrium at 30% RH. Of course, wood takes a while to equilibrate to changes in RH, and film finishes further slow the change, but wood begins to move with any change in RH and will change a lot if the difference in RH is large enough and lasts long enough. We've all seen sticky doors and drawers in the Summer and gaps in wooden floor boards in the Winter. Environmental controls can help minimize this expansion/contraction, but good design and thoughtful construction will allow the piece to survive even without controls.
John
Contributor
I live in central California so my humidity is reverse of yours dry in summer and damp in winter. I looked it up and San Francisco, whose climate does not vary that much, has a 20% change in RH over the seasons.
Bil lD
Contributor
I suppose the other constant RH is underwater. There are redwood logs buried in rivers and lakes that have not rotted or cracked in centuries but dry them out and they start to twist. Wood wine vats are over 120 years old and still hold liquids fine.
Bil lD
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