Some understanding of wood grain would also be a good idea. I'll loan
you a book or two if you're interested.
The short version of understanding wood movement (aka
expanasion/contraction) is that you should think of any piece of wood
as a bundle of microscopic straws, sucking in or expelling moisture as
the ambient humidity and temperature change. As it does so, it swells
or shrinks.
Maybe hoses is a better analogy, because most straws don't usually
expand or contract that much.
Anyway, the fiber expands or contracts much less in the longitudinal
direction, i.e. the longest dimension of the fiber.
In fact, there are three directions and it makes plenty of sense once
you think it through. Remember tree growth rings?
If you cut a tree trunk in half and look down at the cut face, you're
looking at all these concentric growth rings.
The wood expands/contracts LEAST coming straight at you, i.e. along
the length of the tree trunk.
Second least is diameter expansion, i.e. the width of the tree trunk,
if you measure from the center of the trunk's diameter to the outside.
The official name for this (see below) is radial, but to me that
always sounds like they're talking about the circle expanding.
Third is indeed the circle expanding, called "tangential" (which is
almost certainly chosen to describe how the saw cut's angle relates to
the growth ring's angle). If you think about a
circle expanding, obviously the circumference is going gain more
inches - by a ratio of pi. If the tree trunk expands 1 inch in
diameter, it'll expand 3.14etc inches in circumference.
But remember, cutting the board out of the trunk is tangential to the
growth ring, so the board's tangential expansion/contraction is less
than 3.x times as much as the radial expansion/contraction.
According to the links below, the average ratio of movement is 0.1%
longitudinal, 4% radial and 8% tangential.
Here's a pretty good explanation of it:
http://workshopcompanion.com/KnowHow/Design/Nature_of_Wood/2_Wood_Movement/2_Wood_Movement.htm
...and also an excellent description of how boards are usually cut out
of a tree, with diagrams!
http://workshopcompanion.com/KnowHow/Design/Nature_of_Wood/1_Wood_Grain/1_Wood_Grain.htm
Btw, "Understanding Wood" by R. Bruce Hoadley is an excellent book. I
highly recommend it, but it's expensive. You can probably get it
through the library.
On Mon, Apr 25, 2016 at 9:36 PM, Andrew C. <soshumasamune@xxxxxxxxx> wrote:
Bob,
That's a pretty cool trick, that would definitely work.
I just need to learn how to glue it all together and expect it to stay
together. I imagine there
are joints involved, or at least more to it than just gluing square blocks
together. I keep thinking
just glue wont be enough- there has to be wood keys of somekind between
them. But I don't know.
-Andrew
On Mon, Apr 25, 2016 at 8:10 PM, Robert Berger <bob@xxxxxxxxxxxx> wrote:
You could surface it with a router attached to a long board, as shown
here:
http://www.woodworkersjournal.com/surface-rough-lumber-witha-router/
- Bob
On Apr 25, 2016, at 4:57 PM, Andrew C. <soshumasamune@xxxxxxxxx> wrote:
I would gladly make my own butcher block top- but I have no idea how,
other than
gluing blocks together. Plus, we don't have anything big enough to surface
it after
gluing, I'd need a large mill to flycut the top and shape it.
Chad mentioned someone had done it at hack, made their own butcher block.
Was it you James Hyde? Anyone who can make these, I'm interested in
learning.
-Andrew
On Sun, Apr 24, 2016 at 11:49 PM, Steven Owens <stevenjowens@xxxxxxxxx>
wrote:
On Sun, Apr 24, 2016 at 11:10 PM, Andrew C. <soshumasamune@xxxxxxxxx>
wrote:
Normal butcher block isn't thick enough for me... I want to build an
ergonomic custom bench here that
will survive centuries as a true piece of serious furniture. I want to
go
all in on it, without breaking my
bank... Maybe a lumbermill can cut me something 1pc out of cherry or
hickory
or oak, 3" thick? But
I'm afraid it would warp... It needs to stay very flat for some of the
other
work done on it....
Thicker butcher block is gettable, or not that impossible to make
yourself, which might be kind of cool for you.
If you want to go the lumbermill route, I can talk to some of the
people I've used. One place, I bought a really nice, two full inches
thick plan of white oak from, for a particular use. That stuff is
very massive.
I love big, solid pieces of wood too,but the big problem is cracking
and warping - the thicker and bigger the piece is, the more that's an
issue. I talked to one of the lumbermills about getting a "round"
(i.e. an entire slice of trunk, a big disc). Never did try it, but he
warned that it was very, very likely to split or crack as it dried
out.
Wood "moves", i.e. it expands and contracts with moisture. Wood
*always* moves. Carpenters tend (or at least carpenters have told me)
to avoid large single pieces of wood for that reason. They make more
cuts and they play the grain of the different pieces off against each
other, or they design the bigger pieces to "float", like an old
fashioned door or a nice tabletop.
--
Steven J. Owens
stevenjowens@xxxxxxxxx
puff@xxxxxxxxxxxxx
412-401-8060
