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View cathyb's profile

why so up tight!?

by cathyb
posted 1269 days ago


26 replies so far

View Dez's profile

Dez

1113 posts in 2683 days


#1 posted 1269 days ago

You never know when the universe is going to reach out and slap you up alongside the head!
That is why it pays to PAY attention!
Unfortunately you don’t always no what to pay attention too!
Excellent advice!

-- Folly ever comes cloaked in opportunity!

View spunwood's profile

spunwood

1194 posts in 1442 days


#2 posted 1269 days ago

Thanks for the post. Helpful reminder /warning.

-- I came, I was conquered, I was born again. ἵνα ὦσιν ἓν

View GaryK's profile

GaryK

10262 posts in 2594 days


#3 posted 1269 days ago

My trick to cutting tension wood is to cut it until I start to see it move. Then back it out all the way and start again. That should remove more material to get rid of any binding. As long as the piece it’s too bad I keep repeating this until I’m through it.

I also use a splitter built into my ZCI to keep it from pinching the blade.

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

View cathyb's profile

cathyb

757 posts in 1850 days


#4 posted 1268 days ago

Gary, I couldn’t agree with you more. My riving knife on the saw is my best friend. In this case, it didn’t come into play because I was cutting a dado. Like I said, if I had known that there was tension in that wood- cutting a dado would have been, and certainly was, living on the “wild side”. Oh well….......

-- cathyb, Hawaii, www.cathyswoodworking.com

View ScottN's profile

ScottN

259 posts in 1285 days


#5 posted 1268 days ago

last winter I was doing a dado on a 7hp table saw when I heard the saw starting to bog down and decided to just let go and let the board go flying,But before I could let go… the board was ripped out of my hands and cutting 2 fingers and 1 thumb.

-- New Auburn,WI

View Sawkerf's profile

Sawkerf

1730 posts in 1674 days


#6 posted 1268 days ago

I’m not sure that there’s any way to identify tension wood just by looking at it. I had a piece of pine explode several years ago and it sure spooked me. No injuries, and it hasn’t happened again, but…..... – lol

I have had long boards open up 2” – 3” as I ripped them, but not explode.

-- Adversity doesn't build character...................it reveals it.

View Lee Barker's profile

Lee Barker

2163 posts in 1456 days


#7 posted 1268 days ago

This discussion has really got me to thinking. I can imagine, clear headed and deliberate, short circuiting the cutting of a board if I had clues it was about to become dangerous.

However, I can also imagine that late in the day, on a project with no comfortable cushion of extra material behind me and a looming deadline, not making the wise choice. I hope this story helps me adjust the latter.

My first experience with tension wood was ripping a long piece of 4/4 western cedar decades ago. In the course of that 10’ cut, the two pieces spread way apart and then came back toward each other and crossed!

Kindly,

Lee

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View cathyb's profile

cathyb

757 posts in 1850 days


#8 posted 1268 days ago

Wow!!!!!! That was have been something to see. You just can’t respect wood too much. It’s not a piece of plastic and can be temperamental…...

-- cathyb, Hawaii, www.cathyswoodworking.com

View Vasko's profile

Vasko

271 posts in 1292 days


#9 posted 1268 days ago

Wow, this is a great place to learn. I’ve never even heard of tension wood, I didn’t know it could do that! There is so much to learn, it is mind-boggling. When you’re like me, and don’t know any wood workers, it’s hard to learn. There is a man a few towns away that teaches a week long course for $400.00, but that’s hard to come up with…if I ever do take the class, he may come to hate all my questions, but I’ll be armed with a bunch.

-- - Cindy, texture freak -

View cathyb's profile

cathyb

757 posts in 1850 days


#10 posted 1268 days ago

Vasko this is a wonderful journey. I had no instructors except for books and hard knocks. I am not afraid to fail and know that every project teaches me something new. Keep working at it and one day you will be amazed at how much the process teaches you. Best of luck…....

-- cathyb, Hawaii, www.cathyswoodworking.com

View blockhead's profile

blockhead

1451 posts in 1914 days


#11 posted 1267 days ago

I’m still relatively new to ww. I have not yet come across tension wood. What are the main causes? Knots, figuring, how it is milled, combination? Are there any species more prone to it than others? A couple of people mentioned pine and cedar, so I’m guessing it is seen more in a more knotty type species. Any info would be appreciated.

-- Brad, Oregon- The things that come to those who wait, may be the things left by those who got there first.

View ken_c's profile

ken_c

260 posts in 1768 days


#12 posted 1267 days ago

@ blockhead: The tension comes from within – the cell structure of the wood – there is no way that I have ever heard of to tell if the board will cause trouble. As stated above, all you can do is start to mill and watch/feel closely, then react. Treat each rip – in your head at least – as if it is going to move so you are prepared. I rough cut all my boards oversize before I finial mill – that is length, width and thickness. that way when they move I can still bring them into the right size – but that is a different story then the tension discussion here…

View JJohnston's profile

JJohnston

1577 posts in 1897 days


#13 posted 1267 days ago

Tension (also called “reaction”) wood usually comes from branches. A branch is under continual bending stress its entire life, moreso the more horizontal it is. The wood on the bottom is under compression, and the top is in tension. These stresses are locked in as it grows, so it does crazy things when the bending stress is relieved. This can also happen with a trunk that grew bent, or not vertical.

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

View cathyb's profile

cathyb

757 posts in 1850 days


#14 posted 1267 days ago

Tension wood results from a tree growing under significant mechanical stress. For example, if it somehow survived while growing on the side of a steep hill or exposed to high winds or any situation which forced the compression of the tree fibers. Think of the fibers like a straw. The pressure on those fibers creates a compressive load that forces the fibers to compress and really creates a spring. When those fibers are cut on a saw, the cut releases the stress and it opens up from energy released. It is not common, but it does happen. The thing to remember is that if you have a piece of lumber that is just contemptible and no matter how hard you work to get it milled it just won’t stay flat and it won’t stop twisting- it’s got some tension and stored up and it could come back and bite you. To be sure not all tension wood has so much tension that it will actually hurt you, but you have to be vigilant.
If I can’t cut tension wood into thin strips on my band saw, I toss it. It’s just a shame that I didn’t know that this piece of mahogany was a trouble maker. It was only 14” long, but when it came apart and hit the blade. Those projectiles sure were scary. I found fragments on the other side of my shop and yesterday found one in the wall about six feet behind my saw. That is very scary. I consider myself lucky to have walked away with a cut finger.
Be careful, don’t be spooked, just pay attention to your wood. If it seems more trouble then it’s worth, it just might be. Best of luck to you….........

-- cathyb, Hawaii, www.cathyswoodworking.com

View dbray45's profile

dbray45

2482 posts in 1382 days


#15 posted 1267 days ago

I had a piece of walnut explode when ripping. Felt or heard a piece of it go by my ear. I pulled the 4” sliver out of the wall about 20’ (6+ meters) away. Wakes you right up.

-- David in Damascus, MD

View blockhead's profile

blockhead

1451 posts in 1914 days


#16 posted 1267 days ago

Thank you all for your info and sharing your personal experiences! There is such a wealth of knowledge here. I realized some time ago that, the more I know about ww, the more I have to learn. This makes me even more happy that I ordered my Shark Guard. Thanks again

-- Brad, Oregon- The things that come to those who wait, may be the things left by those who got there first.

View miles125's profile

miles125

2179 posts in 2611 days


#17 posted 1267 days ago

Never heard the term tension wood. I’ve always called it banana-ing. As in in springs into a banana shape when ripped, sometimes rather startling. Cottonwood is the worst i’ve ever experienced doing this. But all woods are susceptible.

-- "The way to make a small fortune in woodworking- start with a large one"

View JJohnston's profile

JJohnston

1577 posts in 1897 days


#18 posted 1267 days ago

I’m not surprised to hear that cottonwood does this. There are lots of cottonwoods around here, along the Rio Grande, and the big, mature ones almost invariably have multiple trunks that curve continuously outward to become their own branches at the top.

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

View EPJartisan's profile

EPJartisan

1048 posts in 1731 days


#19 posted 1266 days ago

From what I understand about trees… and I love researching tree species. Reaction wood comes in only a few forms but mainly in two we woodworkers worry about: Compression and Tension. A bit of knowledge anyone can verify… Conifer woods (gymnosperms) can not be in tension, only in compression, and then mostly under the horizontal branches, so cedar and pine will still twist and fold but only in order to expand not relax. Conifers are more “simple” in cell structure than hardwoods, lacking parenchyma cells and acting much more like sponges than structures. Angiosperms have both tension and compression and can form in the wood anyplace the tree was bent, twisted, burled, and Tension wood is always above the tree branch and Compression below. If you study enough wood grain and research how trees grow, you can actually learn how to identify reaction wood before you cut and how to work with them. NO system is perfect and each tree is unique, but over all I can tell where a board will warp, twist, bind or split just by observing the grain and knots.

-- " 'Truth' is like a beautiful flower, unique to each plant and to the season it blossoms ... 'Fact' is the root and leaf, allowing the plant grow and bloom again."

View JJohnston's profile

JJohnston

1577 posts in 1897 days


#20 posted 1264 days ago

I’m not so sure about the “compression only” thing in conifers. It’s a law of physics that if the bottom of the branch is in compression, the top will be in tension; otherwise, “static equilibrium” is violated (all forces add to zero. If there is a force not countered by an equal and opposite one, there will be an acceleration, per Newton’s laws).

I do know that the reaction woods of the conifers and hardwoods have different characteristics, but I don’t remember what they are, or where I read it.

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

View cathyb's profile

cathyb

757 posts in 1850 days


#21 posted 1264 days ago

Hmmm, interesting. Without actually seeing the tree standing before it becomes lumber, it’s hard to anticipate what kind of energy is bond up in those fibers. Thanks so much for making sense of it all….......

-- cathyb, Hawaii, www.cathyswoodworking.com

View EPJartisan's profile

EPJartisan

1048 posts in 1731 days


#22 posted 1264 days ago

Well, gymnosperms lack a few cell types to create real tension (pulling force) in the wood cells. No or few lateral fibers or lateral parenchyma vessels, they also do not have short enough vertical tracheid cell formation in the Xylem layer…. also all branches on gymnosperms start directly from the pith of the tree, no matter how old it is, not from meristem cells in the cambium layer. I am not sure if this explains much, but the physics involved, means each branch is held up from below, not from above, which would cause tension wood. Angiosperms have long fibers and short vessel trachieds making more of a brick AND lattice work holding the tree up from below and from above. It is a matter of biology and cell structure. But like I said.. it can be verified, which is the nice thing about science. But seriously cathyb, looking at a whole tree one may see where the more obvious stresses can be, but external examination can easily miss internal aspects like over grown knots and cell decay. The only way most of us woodworkers will ever know is by learning the material and how much is totally up to the individual. And like I said, every tree is unique, meaning each board can be a surprise… which is why I love the medium, love knowing things, love making things.. and love being wrong or making mistakes to refine myself. :)

-- " 'Truth' is like a beautiful flower, unique to each plant and to the season it blossoms ... 'Fact' is the root and leaf, allowing the plant grow and bloom again."

View JJohnston's profile

JJohnston

1577 posts in 1897 days


#23 posted 1264 days ago

Even living things obey the laws of physics without exception, and physics says that a branch will have an equal amount of both tension and compression FORCE at any particular cross section. Now, the wood may not be able to bear as much tensile STRESS (not the same thing as force) as compression; this would mean that greater than half the cross-sectional area is in tension and less than half in compression (and the point of zero stress would be below the center). Average tensile stress would be lower than average compressive stress, but since there would be proportionately more area under tension than under compression, the magnitudes of the tensile and compressive FORCES are equal.

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

View EPJartisan's profile

EPJartisan

1048 posts in 1731 days


#24 posted 1264 days ago

You are correct in your logic for structural building and it can apply to angiosperms (after a fashion), but it does not really fit for gymnosperms. Think a stick in a sponge. Sorry I could not explain it better for you. peace.

-- " 'Truth' is like a beautiful flower, unique to each plant and to the season it blossoms ... 'Fact' is the root and leaf, allowing the plant grow and bloom again."

View EPJartisan's profile

EPJartisan

1048 posts in 1731 days


#25 posted 1262 days ago

I found it… “The Tree” by Colin Tudge

HANDS DOWN the best resource for anyone who wants to learn the full biology of the “tree” part of the plant kingdom. Also includes shrubs, vines, bananas (because they aren’t really trees.) It will give you the full low down on the cell structure and the evolution of those cells from ancient Ginkgo fern trees to complex new species of Angiosperm. Includes why the trees grow where they do and how they do. Utterly fascinating!!!!!!! And he even explains why gymnosperms don’t really develop tension wood while living and why Angiosperms need to stay adaptable to changing environments. I should post this in the reviews area. :) ~ enjoy

-- " 'Truth' is like a beautiful flower, unique to each plant and to the season it blossoms ... 'Fact' is the root and leaf, allowing the plant grow and bloom again."

View Dark_Lightning's profile

Dark_Lightning

1676 posts in 1715 days


#26 posted 1262 days ago

Based on the physics, tension wood would (heh heh, I said wood twice without repeat!) close on the blade, and compression wood would (heh heh, twice, again!) spread open. The tension wood is your real problem, what with pinching the blade. I’ve had it happen. I generally shut off the saw, if it’s bad enough. Never had it explode, though.

One thing, though: It’s the power tool’s energy, not the wood, that is the problem. If you were hand sawing it with a rip saw, it’d get ugly, but there would be no flying pieces.

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