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Wood warping and attaching table top to skirt

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Forum topic by etrain posted 12-17-2015 02:44 PM 565 views 0 times favorited 5 replies Add to Favorites Watch
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etrain

2 posts in 784 days


12-17-2015 02:44 PM

Hello all:

First, I’m new to woodworking, so I will get that out of the way before I proceed. I just recently put together a table top, first one I have made. I milled down 4 pieces of pine to 7” wide by 1 3/8” thick. I joined the pieces/edges using 3/8” dowel pins and of course glue. The table top, now (approx. 27” wide by 40” long) has some warping. It seems like some of the pieces cup warped after I milled them. So I would like to ask some questions if I could and maybe someone could be of some help.

1. Can the table top be flattened? She’s about 1/8” to 3/16” off where she’s warped.

2. Will attaching the skirt help flatten the table? The table will support a miter saw, about 65 lbs. or so.

3. Is it a good idea to use Z clamps or should I use pocket holes when attaching the skirt? Is there a good way to keep paint out of the 3/32” groove for the Z clamps…tape?

4. When I buy lumber, should I set it flat on the floor of my basement (concrete), on its’ edge, stand it up, floating on a magic carpet? 

5. How long should I store it before milling? Watching the wood I have, it appears it may take 3 weeks to acclimate. I do use a dehumidifier.

6. When using dowel pins or biscuits, do I need to use the method, if you will, where I used parallel clamps and cauls (spelling?)? I’m just learning about this method.

Thanks for reading!


5 replies so far

View SirIrb's profile

SirIrb

1239 posts in 690 days


#1 posted 12-17-2015 03:07 PM

Problem 1 is that if this is construction grade pine the moisture content was probably too high at the time of purchase to put into action. Next time let it set in a nice dry climate for some time.

Problem 2 is you want to flip the boards for glue-up. if you are looking at the end grain then one is a smile the other is a frown the next is a smile and so on.

But its cupped…. I know. How to resolve the issue? Thats why you posted. I would rip the top back into separate boards and follow the above #1 and #2.

-- Don't blame me, I voted for no one.

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SirIrb

1239 posts in 690 days


#2 posted 12-17-2015 03:08 PM


Problem 1 is that if this is construction grade pine the moisture content was probably too high at the time of purchase to put into action. Next time let it set in a nice dry climate for some time.

Problem 2 is you want to flip the boards for glue-up. if you are looking at the end grain then one is a smile the other is a frown the next is a smile and so on.

Problem 3 is you need to alternate clamp location. If you have 8 clamps on it you want the first on bottom the second on top the third on bottom and so on.

But its cupped…. I know. How to resolve the issue? Thats why you posted. I would rip the top back into separate boards and follow the above #1 and #2.

- SirIrb

Sorry, tried to edit and made a dumb post. see #3 in the above for edit.

-- Don't blame me, I voted for no one.

View a1Jim's profile

a1Jim

115201 posts in 3036 days


#3 posted 12-17-2015 04:01 PM

etrain
Like sirib said the kind of wood you using makes a difference ,construction grade material still has a lot of moisture in it,your better off build with wood that has been kiln dried,this will limit the kind of cupping your now experiencing. Another reason wood cups is because one side is drying faster than another so it’s best not to have wood laying flat on a bench because the top will dry quicker than the side laying flat. To try and flatten out your table top use a damp sponge and dampen the convex side of the cup., you might have to do it more than once to get results.
You never want to screw a table top down with pocket screws. I know there are people on line that do this but it’s asking for trouble,because of wood movement. Here’s a link that will help you understand about moisture content and wood movement.

http://toddpartridgedesign.com/sr_pages/documents/UnderstandingWoodMovement.pdf

-- http://artisticwoodstudio.com Custom furniture

View OSU55's profile

OSU55

1056 posts in 1449 days


#4 posted 12-17-2015 06:57 PM

If you use cauls they will align the pieces. Dowels don’t add strength and biscuits don’t do much of anything. Edge joints provide all the strength needed and cauls are much easier to use vs fritzing with dowels. Cauls are easy to make from 2×4

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HokieKen

1735 posts in 598 days


#5 posted 12-17-2015 08:02 PM

All of the above is good information. If it were me, I’d let it sit until I was sure it had stabilized before I fixed it. You could take that amount of cup out with a hand plane. Your aprons might also pull it out. Just attach the aprons on the cupped (concave) side and pocket screw them on AT THE CENTER ONLY. Use Z clips, buttons or figure 8s on the ends to allow for movement. Normally I wouldn’t even use screws at the center but if it pulls the bow out for you then I’d go for it. I’d get some stabilized 8/4 kiln-dried lumber for the aprons. If you use construction lumber, it may exaggerate the bow you already have.

-- Kenny, SW VA, Go Hokies!!!

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