Stolen without permission from:
"A 36" wide top, made with flat sawn lumber, can move more than an inch
with a 10% change in moisture content."
That comment was included in the following paragraph:
"Allow tops to move freely. Attach tops with Figure 8 Connectors, Z clips,
shop made blocks or elongated screw holes. All of these methods will
securely attach the top but all (sic) it to move across its width. A 36?
wide top, made with flat sawn lumber, can move more than an inch with a 10%
change in moisture content."
I'm pretty sure that a Figure 8 connector is not going to handle movement
of "more than an inch" unless it's a *really* big one. ;-)
Well, it's not a mistake in terms of what's possible, but it assumes the
10% is an absolute MC, not relative to dry. Absorbing 10% absolute
moisture would require soaking it and maybe not even then...
The amount of shrinkage calculated is:
1 3/32 inches
(rounded to nearest 1/32 inch)
The information you entered was:
Width: 36 inches
Initial Moisture Content: 0.1 (decimal percentage value)
Final Moisture Content: 0.2 (decimal percentage value)
The type of lumber you chose was: Flat Sawn
The Shrinkage Percentage Value used for
the species you chose (Oak, Northern Red) was: 8.6%
If you assume 20% of stable, so 10% to 12%, you get the more reasonable
answer of something like 1/4"...
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An inch sounds like a lot ver just 36". But depending on the wood and
amount of moisture content it can happen.
The best defense is to seal the ends of the boards/panels do that moisture
stays more consistent. Sealing all exposed surfaces is even better.
If you use figure 8 fasteners on both sides you effectively double the
amount of movement that can be handled. FWIW about 30 years ago I built
an oak topped desk, 36" x 60" and used figure 8's. No issues so far.
Not sure any wood would change 10% after coming to equilibrium. 10%
would be a huge change, more like 2-3% ...would be normal, I would think.
So if 10% change, yea maybe 1".. but that's not a practical moisture change.
When my biscuit jointer was new, that's the first thing I tried doing.
It didn't work out so well. Too much slop in the joint. The biscuit
was pretty much useless. The jointer has now been used *once* and
it'll likely stay that way until my heirs sell it on ebay.
Puckdropper <puckdropper(at)yahoo(dot)com> wrote in
Is a bisquick joiner something you use in the kitchen? ;-)
I used mine, right after I got it, for a couple of panel glue-ups, and concluded that it provided
no advantage over edge-gluing and clamping -- in fact, it took longer, was more work, and
produced sloppier results.
And then it sat gathering dust.
Until it was time to remodel the kitchen, and I had a whole bunch of face frames to make.
Then, it got used a *lot*.
I've also found that the #20 setting is ideally suited to cutting slots in the apron of a table, for
inserting z-clips to attach the top.
There's enough play in the biscuit slots, and enough variability
in the thickness of individual biscuits, to allow for noticeable
misalignment in an edge-to-edge glue-up, enough to leave a ridge
that's too big to remove with just a few passes with a card
scraper. I found that I can get better alignment, faster, without
I understand how that can happen but I've not really had problems with
it. I've been using Porter Cable biscuits and keep them in a pretty
stable environment so they don't swell.
I did once use a bag of generic biscuit and found more variation though.
On Fri, 19 Aug 2016 02:49:04 -0000 (UTC), Doug Miller
If I couldn't trust it to align flat panels to each other (with the
help of clamps and cauls), I figured there was no point in even trying
anything more complicated. There are too many other joinery
techniques to bother with it anymore.
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