Wood cup/warp

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Forum topic by cdhilburn posted 10-28-2011 12:54 AM 1890 views 0 times favorited 10 replies Add to Favorites Watch
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102 posts in 2648 days

10-28-2011 12:54 AM

Topic tags/keywords: maple cupping warp

I spent most of last night planing some maple in preparation for beginning to build some Christmas gifts. I went out to the shop a couple of hours ago and the boards are warped, cupped, crooked. They are so out of shape I don’t know if I can use them. I have only been actively woodworking for a year or so hence I am basically a newbie. It hasn’t rained, the temp is about the same. What am I missing? Thanks – Darren

10 replies so far

View reggiek's profile


2240 posts in 3234 days

#1 posted 10-28-2011 01:15 AM

First of all…is that wood dry or green? Has it been kiln dried, air dried? These factors affect how much moisture is in the wood fibres at any time. Wood fibres are pliable in water (as any steam bender knows)....but when the water is forced away – through evaporation perhaps….the fibres stiffen and contract….this contraction goes towards wherever there is room for them to go. Along with the reduction of moisture….there is also internal stress – as a tree grows….the limbs become extremely heavy….and the wood grows in directions to support them….when the limbs are removed….there is alot of tension released…and the wood moves. Alot of these forces can be worked with so that the wood does not become a crooked mess…..

To remedy some of these problems it is recommended that you get an idea of the moisture content of the wood you buy, cut or are given. If it is above 15% or so….you will need to dry it a bit before working (wood that still needs to dry will always bend somewhere). Once the wood is down to around 10-12% it is ready to work…..I still recommend that you let wood acclimitize….sit in your shop for awhile so that it’s moisture content matches the ambient humidity in your shop. If you must work the wood prior to letting it acclimitize…I recommend that you rough out the piece…let it dry completely….and then finish.

If a board becomes cupped or warped….you can still cut it to smaller pieces and use it. You would need to follow the above and then re-mill the smaller pieces. When I have had this problem in the past….I would mill the wood flat again (in smaller pieces) and glue it back up into sizes that I need.

-- Woodworking.....My small slice of heaven!

View cdhilburn's profile


102 posts in 2648 days

#2 posted 10-28-2011 01:25 AM

It was kiln dry before I bought it. It has been in my shop for almost 9 months and I have used 2-3 boards for other projects with no problem. I had to take it down alot. I am going from 13/16 to 5/16. My bandsaw will not resaw that high and I haven’t found anyone locall yet to help me out. I wonder if going doen to 9/16 and then waiting a couple of weeks to finish it will help? BTW….I was sick when I saw the first board warped on my table saw.

View chrisstef's profile


17305 posts in 2970 days

#3 posted 10-28-2011 01:53 AM

Darren, you took off about a 1/2” of thickness and my guess is that you may have exposed some undried timber which when drying in your shop twisted up on you. This is my best guess and im sure someone else will chime in soon enough. Either that or the board had some stress points in it and once exposed went hog wild on ya. Good Luck man.

-- Its not a crack, its a casting imperfection.

View ChuckV's profile


3110 posts in 3491 days

#4 posted 10-28-2011 02:02 AM

Did you plane equal amounts off of each board face? In other words, did you remove about 1/4” from each side. This helps to keep things in equilibrium.

I wish you the best.

-- “Big man, pig man, ha ha, charade you are.” ― R. Waters

View cdhilburn's profile


102 posts in 2648 days

#5 posted 10-28-2011 02:06 AM

Thanks fellas. This all makes sense. I took material off of each side but to say equal I really don’t know. Wifey called me in for dinner about halfway through and all progress was forgotten. I think I will try another board tonight and just take a little off each side and then wait a few days. As long as I get to this in the next 3-4 weeks I should be okay. I have other gifts I can make out of the thicker stock. Maybe its time for the riser block for the bs.

View cdhilburn's profile


102 posts in 2648 days

#6 posted 10-28-2011 12:11 PM

Thanks…the knowledge is what is great about this site.

View MoshupTrail's profile


304 posts in 2445 days

#7 posted 10-28-2011 12:53 PM

I have seen wood do that but mostly when it was a poor piece to begin with. By that I mean the tree was growing on a slope, or perhaps the wood was taken from a branch. In both those cases the wood contains large internal stresses that will make it bow and twist every time you take a slice off either side. You say it sat there fine for many months and only moved after you took some off. That definitely means there were internal stresses. Yet, other boards did not do this. Were they all from the same tree? I am suspicious of your wood source.

Cutting it smaller and re-gluing might help – especially if you can re-glue it reversed – so it counter stresses itself, but that can add a lot of work to a project.

I would not buy wood from that source again. Oh, by the way, if I’m right, taking more off will not help.

-- Some problems are best solved with an optimistic approach. Optimism shines a light on alternatives that are otherwise not visible.

View WDHLT15's profile


1731 posts in 2440 days

#8 posted 10-29-2011 01:57 PM

You wood in the inside was not in equilibrium with the temp and humidity in you shop because cup and warp result as a drying defect. When you planed the wood down to the narrow dimension, that exposed the middle interior of the board. Because it was not in equilibrium, moisture was gained or lost and that created the stress to cup and warp.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT40HD35 Sawmill. Nyle L53 Dehumidification Kiln.

View jeepturner's profile


939 posts in 2756 days

#9 posted 10-29-2011 02:09 PM

When I cut maple, kiln dried, acclimatized to my shop, I expect movement. With any other wood treated with the same respect for drying I don’t get the same effect. I expect that I will have hidden stresses in maple.
I am not discounting what was said above about how to mill your maple, I am just advising to expect maple to move, and mill accordingly. Cut wait and cut again, then sometimes repeat and calculate waste accordingly.

-- Mel,

View EPJartisan's profile


1118 posts in 3089 days

#10 posted 10-31-2011 09:11 PM

LOL.. ditto for all of the above. I honestly think of wood as still alive and I must think it can hear me for how much I yell at a board. I got some hickory flooring from a client. needed to plane it down from 3/4” to 1/2” and 1/8” with each cut the boards twisted one way.. then the other, and the next day I could cut 1/16 (or less) off it again until I made a stable core. added a few extra days on the project.

-- " '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."

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