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Forum topic by spunwood posted 01-16-2012 04:55 AM 1592 views 0 times favorited 19 replies Add to Favorites Watch
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1202 posts in 2830 days

01-16-2012 04:55 AM

Topic tags/keywords: shrinkage movement mitre miter miters open opening gap question help

Here is a microwave shelf I made:

And here are the miters a few months later in winter:

I used dried wood (barnwood).
I may remember the pieces for the miters being a hair too small or big, but working in the glue and clamping.
Is it the wrong size wood miters, no biscuits, any thoughts?
Would you repair them?

Appriciate your insight,

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

19 replies so far

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1202 posts in 2830 days

#1 posted 01-16-2012 04:59 AM

Could the microwave be increasing the drying effect?

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

View doughan's profile


96 posts in 2585 days

#2 posted 01-16-2012 05:02 AM

can you take a picture with a straight edge held up to the sides?

my guess is that the wood continued to dry,the middle of the edge moulding between the miters stayed glued up and the area near the miters the glue joint popped …can we see what it looked like when it was first down to rule out carpentry skills(yeah I’m kidding)

View Nighthawk's profile


556 posts in 2350 days

#3 posted 01-16-2012 05:09 AM

You say later in winter when there is more moisture in the air…? It looks like it has expanded> Something is not sealed properly… and moisture getting in…

maybe hard to say…

-- Rome wasn't built in a day... but I wasn't on that job? ...

View EEngineer's profile


1102 posts in 3607 days

#4 posted 01-16-2012 05:21 AM

Hmmm, how wide is this piece? Wood tends to grow/shrink across the grain. In winter, the air is drier and the wood will shrink. It looks like that is exactly what happened with your mitered corners. The center panel shrank across the grain and the end pieces, being with the grain didn’t shrink or didn’t shrink as much.

Did you seal the top and bottom of this shelf? It helps to seal it all but the wood will still grow and shrink with changes in humidity. With this design there is probably not much that will help. Next time, leave the edges along the grain as they are and try simple caps on the open end grain. Fasten the caps securely in the center and allow the ends to “float” using slotted screw holes. You can also use a simple dovetail joint, glued in the center with both ends unglued to allow the center panel to expand and contract.

-- "Find out what you cannot do and then go do it!"

View Grandpa's profile


3259 posts in 2669 days

#5 posted 01-16-2012 05:27 AM

Oak plywood for the center would have probably prevented this but then you would have a barnwood shelf. I have made these using plywood with no problems. I would probably band the ends and the front leaving the back open.

View a1Jim's profile


117086 posts in 3571 days

#6 posted 01-16-2012 05:44 AM

It looks like your dealing with wood moment.

-- wood crafting & woodworking classes

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4717 posts in 2345 days

#7 posted 01-16-2012 06:05 AM

The problem is that the wood shrank across it’s width, the end pieces did not because wood shrinks not at all longitudinally, you have to allow it to “float” with every change in humidity. The fix is to not confine wood movement in a frame like you have here. A better solution would have been to leave the frame off and rout a nice profile on the edge to give it a more finished look, a simple chamfer would do.

-- Bondo Gaposis

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47 posts in 2339 days

#8 posted 01-16-2012 06:38 AM

Depending on his location, winter can be drier months. When it gets cold, air can’t hold as much moisture. Which would suggest drying and shrinking. Wood changes dimension most on the face grain (tangential) of plain sawn boards. The next greatest change is radial (the width of quarter sawn boards). The least change is longitudinal (along the length of any board). When your wood dried more, the most severe shrinkage was along the width of your figured board, due to the presence of many layers of grain that are tangential to the face. The longitudinal shrinkage was minimal, making the face boards pull away from your mitered border. You’ll notice that your mitered joints are still very tight, that’s because your did a good job, and the longitudinal shrinkage of the joined boards cancelled each other out. Solution? Quarter sawn boards (boring) or, spring joint, in which you have a little extra wood on the ends where it tends to pull away because of the weakness of end grain gluing. I would go the spring joint route. – Rich

-- - Rich

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47 posts in 2339 days

#9 posted 01-16-2012 06:40 AM

Looks like I was beat to the punch! – Rich

-- - Rich

View fussy's profile


980 posts in 3044 days

#10 posted 01-16-2012 08:05 AM


It’s hard to tell for sure, but I laid a straight edge across the screen and it loooks as if the molding bent at the corners. Pictures 3 & 4 shows the bend quite clearly. The miter joints themselves are just fine. The material itself warped. Could the short side have been too long allowing the moisture introduced by the glue have caused the long sides to bend at that end? My vote is too long short side forcing long sides to bend. I would put the microwave back on and not mention it.


-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

View spunwood's profile


1202 posts in 2830 days

#11 posted 01-16-2012 01:54 PM

Fascinating. Some interesting suggested solutions too.

EEngineer—what do you mean by ‘caps’?

Thanks, next time I build something similar, I will take my design to LJ’s first!


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

View Dusty56's profile


11819 posts in 3682 days

#12 posted 01-16-2012 02:22 PM

Mother Nature versus Man….seasonal movement is a real bugger to deal with.
I believe that EE was referring to “breadboard” ends. Google it : )

-- I'm absolutely positive that I couldn't be more uncertain!

View tbone's profile


276 posts in 3678 days

#13 posted 01-16-2012 05:50 PM

Breadboard ends IS a good solution, but it’s a lot of trouble for a microwave shelf. I think I’d just leave off the mitered frame and do a nice routered edge. Dried or not, that flat sawn red oak is going to move with the climate no matter what you do, so just give it some room to move and you’re done.

-- Kinky Friedman: "The first thing I'll do if I'm elected is demand a recount."

View rance's profile


4258 posts in 3154 days

#14 posted 01-16-2012 06:05 PM

A1Jim and Bondo have properly identified the cause. Wood is constantly moving, and will until you burn it. You assembled a ‘cross grain joint’. If you like this design, you’ll have to accomodate for the wood movement such as has been mentioned(breadboard ends). You’ve just had an education and experience in ‘Fine Woodworking 101’. Learn from it and accomodate for it in your next project. As another example, look in to how they make raised panel doors for kitchen cabinets. The panels are loose to accomodate for wood movement. As it has also been mentioned, plywood can be used to prevent such problems. You’ve got the cause identified. Now you’ve got some googling and reading to do. Let us know if you have any more questions.

Fussy-FWIW, the trim did not warp and cause the problem. What you are looking at with the trim is a result of the problem, not the cause of it.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

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153 posts in 2673 days

#15 posted 01-17-2012 12:12 AM

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