Great article on wood shrinkage.

[chopnhack]

Popular Woodworking Magazine put out a great article on wood shrinkage, very well written:

http://www.popularwoodworking.com/vi...3&rid=19343928

[cabinetman]

That is an interesting article. The inputs for determining the range do fit for the most part. It is though, a general method, and as I've found out that it seems that wood can have a mind of its own. Especially here in tropical climates, what you have when the lights go out, and get turned on the next morning can reveal some surprises.

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[BigguyZ]

Or just ask a woman about shrinkage. I think women know about shrinkage...

[leehljp]

That was interesting. I read similar in Hoadley's book "Understanding Wood" (I think that is the name.) That book really helped me understand and plan in building. This article is the same.

BTW, the reason for the wood in wood handled hammers getting loose is because the the expansion and contraction factor more than anything else. Fairly dry wood is used; it sets for a season or two in humidity changes, expands to the point it damages the cells against the metal head, then a dry season comes along and it shrinks again; repeat with a very humid season in which it expands more and more cells crush against the metal head; lastly a dry season will shrink it again and it is loose! Wood Moves!

[chopnhack]

Its been a long time since I perused Understanding Wood, but somehow this article seemed to be easily understood and digested... I guess it was quick and to the point.

[cabinetman]

Its been a long time since I perused Understanding Wood, but somehow this article seemed to be easily understood and digested... I guess it was quick and to the point.

The article was quick and to the point, but using the calculations are a bit more involved. I don't see much value other than some range of possibilities that would require me to spend the time to figure shrinkage. My point is, that the results of the calculations are more of a point of interest than necessary data.

In actuality, even with a range of possibilities, I wouldn't use dimensions arrived by that calculation for anything with an assumed predictability. What happens is that we know about and allow for movement issues, but not to any dimension.


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[leehljp]

These movement issues is why I sometimes question the beautiful checkerboards and checkerboard designed cutting boards. With each block of wood 90° to each other, I can't see how most of them will maintain a new like fit a year later. And mitered ends of frame around the checkerboard will make it even more pronounced.

Actually, before hoadleys book, I learned personally about this truth on several occasions. The book allowed me to bring everything together as to the cause and how to avoid it. I still don't see how it can be avoided because of humidity changes.

[cabinetman]

These movement issues is why I sometimes question the beautiful checkerboards and checkerboard designed cutting boards. With each block of wood 90° to each other, I can't see how most of them will maintain a new like fit a year later. And mitered ends of frame around the checkerboard will make it even more pronounced.

Actually, before hoadleys book, I learned personally about this truth on several occasions. The book allowed me to bring everything together as to the cause and how to avoid it. I still don't see how it can be avoided because of humidity changes.

The thinner and smaller in size the pieces are lessens the likelihood of movement. A good finish slows down the possibilities too.

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[woodturner]

Its been a long time since I perused Understanding Wood, but somehow this article seemed to be easily understood and digested... I guess it was quick and to the point.

I agree - this article provides a simpler way to calculate the information woodworker's need to accomodate for wood movement. Hoadley is "more complete" but the additional accuracy and detail provided is not needed to accomodate wood movement in actual woodworking projects.

The article method provides an accurate measure of annual wood movement and is sufficient to allow for wood movement when designing and building projects. I think it's better to have a simple method that people may actually use - it give better results than the usual method of just using a "rule of thumb".

[woodturner]

These movement issues is why I sometimes question the beautiful checkerboards and checkerboard designed cutting boards. With each block of wood 90° to each other, I can't see how most of them will maintain a new like fit a year later. And mitered ends of frame around the checkerboard will make it even more pronounced.

In high school, one of the second year woodworking projects was a chess board - 3/4" maple and walnut squares glued up to form the chess board. It was a good introduction to efficiency and production woodworking techniques. However, the grain ran the same way on the squares, so serious movement issues were avoided.

Sounds like you are referring to squares of the same wood with different grain orientation, and thicker wood than veneer. Unfortunately, the physics of wood movement prevent that configuration from working very well - even if you can get a reasonable end grain glue joint, the differential movement will quickly pull the joint apart. As you note, the miter joints will also open up.

If one HAD to make such a panel, my guess is that the best bet would be to glue the whole thing to a substrate with a semi-flexible glue such as titebond yellow glue. That would at least hold the pieces down and allow for a little movement, so you wouldn't have lose squares coming off the top.

[leehljp]

In high school, one of the second year woodworking projects was a chess board - 3/4" maple and walnut squares glued up to form the chess board. It was a good introduction to efficiency and production woodworking techniques. However, the grain ran the same way on the squares, so serious movement issues were avoided.

Sounds like you are referring to squares of the same wood with different grain orientation, and thicker wood than veneer. Unfortunately, the physics of wood movement prevent that configuration from working very well - even if you can get a reasonable end grain glue joint, the differential movement will quickly pull the joint apart. As you note, the miter joints will also open up.

If one HAD to make such a panel, my guess is that the best bet would be to glue the whole thing to a substrate with a semi-flexible glue such as titebond yellow glue. That would at least hold the pieces down and allow for a little movement, so you wouldn't have lose squares coming off the top.

I agree 110% . What I am referring to more than anything else is that if we notice the cutting boards that are posted here are solid. My memory may be wrong but, it seems like the vast majority of cutting boards (in checkerboard fashion) are different types of wood, in different orientation, and are not veneered. They come out looking outstanding but I have wondered about the long term viability of such.

Most open grained woods seem to move more than closed grain woods, so purple heart and maple would seem to me to be a problem in the long run. So would walnut and maple, or cherry and most oaks, or mesquite (doesn't move) and most open grained woods.

[chopnhack]

I agree 110% . What I am referring to more than anything else is that if we notice the cutting boards that are posted here are solid. My memory may be wrong but, it seems like the vast majority of cutting boards (in checkerboard fashion) are different types of wood, in different orientation, and are not veneered. They come out looking outstanding but I have wondered about the long term viability of such.

Most open grained woods seem to move more than closed grain woods, so purple heart and maple would seem to me to be a problem in the long run. So would walnut and maple, or cherry and most oaks, or mesquite (doesn't move) and most open grained woods.

Aren't most of the those cutting boards glued such that the end grain is facing up - the surfaces that are glued together are the long grain? I would think that this is a fairly stable orientation.