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Just learned somethign about grain....

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Forum topic by harriw posted 12-13-2012 12:36 AM 725 views 0 times favorited 8 replies Add to Favorites Watch
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harriw

85 posts in 863 days


12-13-2012 12:36 AM

Hey folks,

I just learned something the hard way that I’m sure most of you already knew. But I thought it was interesting so I figured I’d share :)

I’m ripping some 1” thick strip of maple around 3 1/2 feet long. One piece was going to become strips 2.5” and 1” thick. I looked closely at the grain, and saw it was fairly straight for most of the board, then curled around quite a bit on the last inch. I figured making the cut there would make for 2 uniform, but uniquely different end grains for the board.

Well, I went ahead and made my cut, and the 2.5” piece looks great. But when I picked up what was left to shave it down to 1”, I was surprised to find it’s now badly curved! Almost 1/4” off in the center of the board.

I should note here that all the lumber was jointed, and I made sure I ran the opposing edge through the saw to make sure all the boards were true and parallel on both edges before I started ripping.

I think what happened is that the straight grain was keeping it in line. As soon as I removed it, the curly grain on the side bent the way it naturally wanted to, now that the straight grain “next door” was no longer attached.

Oh well – fortunately I have enough extra to make a new 1” strip. But I’ll definitely be on the look-out for that in the future! I never would have expected the board to move out of true simply by removing part of it :)

-- Bill - Western NY


8 replies so far

View WDHLT15's profile

WDHLT15

1130 posts in 1132 days


#1 posted 12-13-2012 03:14 AM

It was caused by growth stress in the lumber. Nothing that you can do about it except when you see it, rip your stock oversize. Once the growth stress is released, you can joint the boards straight.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT15 Sawmill. Nyle L53 Dehumidification Kiln

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Tedster

2271 posts in 867 days


#2 posted 12-13-2012 03:37 AM

I learned about growth stress when doing a compound miter cut on a 2×12. The wood pinched the blade so tight I couldn’t finish the cut or even lift the blade out of it. I had to lift the board, still attached to the blade, and use a hand saw to cut the board from the other side just to get it off the blade. Oddest thing is the board was straight as can be. Never would have seen that one coming, even now that I know about stress.

-- I support the 28th Amendment. http://www.wolf-pac.com/28th

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a1Jim

112096 posts in 2233 days


#3 posted 12-13-2012 03:41 AM

Even wood that’s dry still can have surprises for us.

-- http://artisticwoodstudio.com Custom furniture

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harriw

85 posts in 863 days


#4 posted 12-13-2012 03:56 AM

Nice to hear I’m not the only one that learned that one the hard way :) I was actually able to use it anyway – the pattern i was making had some thicker strips (~3”) on each end so I was able to easily pull it back true with the clamps during glue-up. Thanks for the explanation!

-- Bill - Western NY

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Tedster

2271 posts in 867 days


#5 posted 12-13-2012 04:15 AM

Jim, the wood I was cutting was bone dry. I guess one edge wanted to bend and the cut I started finally allowed it to.

Bill, grain stress can cause a lot of not-so-good things to happen. For instance, it could pinch the back edge of a table saw blade and throw the lumber right back at you – a very dangerous thing. I do a lot of carpentry work. One thing I’ve learned is with my worm drive saw to always hold the saw as if it could kick back at any time without warning. Even when a board is cutting like soft butter, I hold the saw as if I’m fighting with it, just in case I suddenly have to.

-- I support the 28th Amendment. http://www.wolf-pac.com/28th

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bondogaposis

2528 posts in 1007 days


#6 posted 12-13-2012 05:23 AM

There can be a lot of internal stresses in wood that are released when ripping. They can cause kickback too, so be careful.

-- Bondo Gaposis

View Nomad62's profile

Nomad62

710 posts in 1614 days


#7 posted 12-13-2012 11:28 PM

Indeed wood does have that tendancy, especially if it is dried too quickly and develops a case hardening; oak is really bad. Ripping boards is always testy, the stress unloading and clamping down on the blade can send said board across the room or right at you. Some people I know do not rip long boards on anything but a bandsaw for that reason. Thanx for the info on your experience, it helps us all.

-- Power tools put us ahead of the monkeys

View WDHLT15's profile

WDHLT15

1130 posts in 1132 days


#8 posted 12-14-2012 01:00 PM

Here is a link to a good article on growth stress.

http://www.fs.fed.us/ne/newtown_square/publications/technical_reports/pdfs/2004/316papers/Cassens1GTR316.pdf

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT15 Sawmill. Nyle L53 Dehumidification Kiln

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