LumberJocks

Pine table starting to cup. Help!

  • Advertise with us

« back to Wood & Lumber forum

Forum topic by Scotsdevil posted 10-20-2018 02:29 PM 420 views 0 times favorited 9 replies Add to Favorites Watch
View Scotsdevil's profile

Scotsdevil

4 posts in 27 days


10-20-2018 02:29 PM

Topic tags/keywords: question pine

A few weeks ago i built a 10 foot pine dining table however the edges are starting to bend upwards slightly and I’m worried it might get worse over time. The construction is 5×10 foot boards each 2” thick and 7” wide. The boards have full length tongue and grooves and are glued together. The table sits on two trapezium metal legs.

Is there something i can do now that will stop further movement?

Thanks in advance
A novice, self taught, wood worker


9 replies so far

View bondogaposis's profile (online now)

bondogaposis

5049 posts in 2524 days


#1 posted 10-20-2018 02:34 PM

Did you use construction lumber?

-- Bondo Gaposis

View Scotsdevil's profile

Scotsdevil

4 posts in 27 days


#2 posted 10-20-2018 02:45 PM

I think so it was from a timber supplier. Its Scandinavian pine that was kiln dried. Moisture content was around 14% when i began working on it.


Did you use construction lumber?

- bondogaposis


Did you use construction lumber?

- bondogaposis


View Smitty_Cabinetshop's profile

Smitty_Cabinetshop

15647 posts in 2791 days


#3 posted 10-20-2018 02:51 PM


Is there something i can do now that will stop further movement?

Thanks in advance
A novice, self taught, wood worker

- Scotsdevil

Scotsdevil, there are several truths in woodworking and none more important that this one: Wood moves.

Doesn’t matter if it’s dried for 75 years, wood has to move. Especially cross-grain, as you’re finding out. Bondo’s question speaks to construction lumber being kiln dried OR stored outdoors OR not being fully acclimated to conditions (temp and humidity) found in the room in which the table will live.

You can plane it smooth, but until it’s done with the ‘big moves’ the wood wants to make, resistance is futile. And then, when it is planed smooth, air will get to the wood and it will move again. Large furniture projects featuring solid wood are sometimes brutal teachers.

Others will certainly add their inputs. Sorry I wasn’t more positive, you’re facing a serious challenge.

-- Don't anthropomorphize your handplanes. They hate it when you do that. -- OldTools Archive --

View Scotsdevil's profile

Scotsdevil

4 posts in 27 days


#4 posted 10-20-2018 02:56 PM

Thanks for the leason smitty appreciate your honesty. I guess i will wait and see what happens after a few months and hope for the best!

Is there something i can do now that will stop further movement?

Thanks in advance
A novice, self taught, wood worker

- Scotsdevil

Scotsdevil, there are several truths in woodworking and none more important that this one: Wood moves.

Doesn t matter if it s dried for 75 years, wood has to move. Especially cross-grain, as you re finding out. Bondo s question speaks to construction lumber being kiln dried OR stored outdoors OR not being fully acclimated to conditions (temp and humidity) found in the room in which the table will live.

You can plane it smooth, but until it s done with the big moves the wood wants to make, resistance is futile. And then, when it is planed smooth, air will get to the wood and it will move again. Large furniture projects featuring solid wood are sometimes brutal teachers.

Others will certainly add their inputs. Sorry I wasn t more positive, you re facing a serious challenge.

- Smitty_Cabinetshop


View jmos's profile

jmos

891 posts in 2542 days


#5 posted 10-20-2018 04:14 PM

As Smitty said, the best dried lumber is going to move with changes in humidity. What you are trying to do in a good design is allow for that movement.

With a table top there are a few time tested methods for trying to keep the top flat and still let it expand and contract across the grain (movement in the thickness isn’t usually an issue, but does happen, , and movement along the length is usually negligible.)

You can use an apron, where you use a fastener (buttons or Z clips are common) that will secure the top to the apron. You would typically fix the top (on the edge running across the grain) in the center, and then allow the fasteners to slide back and forth toward the edges of the table. Whether it’s on long or short edges depends on how the grain is running in your tabletop. The sides that run with the grain of the board need to be allowed to slide in and out, as the table expands. When done correctly, you hold the top tight to the aprons, and flat, and constrain the motion, but you can’t stop it.

Battens are another method. You run the battens across the grain, then fasten the top tight in the center and allow the fasteners to move toward the edges. This is typically done by making the holes in the batten a slot, instead of a round hole. In your case, if you have metal legs that include a horizontal piece under the table, you may be able to use additional fasteners to hold the top down, just slot the holes so the top can still move, or something will give.

Battens can also be installed in the bottom of the table top using a sliding dovetail joint, or a tapered sliding dovetail joint.

You can also add breadboard ends to try to control cupping. If you’re not familiar with this Google and Youtube can help. Again, it’s usually fixed in the center, and allows movement out toward the edges. This only really works if the grain on the table is running with the length of the table.

Good luck.

-- John

View Scotsdevil's profile

Scotsdevil

4 posts in 27 days


#6 posted 10-22-2018 12:06 PM

Thanks for the advice jmos I will attempt some this weekend

View Richard Lee's profile

Richard Lee

185 posts in 948 days


#7 posted 10-22-2018 05:48 PM

Did you alternate the grain pattern ?

View AZWoody's profile

AZWoody

1411 posts in 1397 days


#8 posted 10-22-2018 06:20 PM



Did you alternate the grain pattern ?

- Richard Lee

With 7” wide boards alternating won’t do much. Each board is wide enough that the cupping will happen to each one. Even with alternating boards, the table will look like an oversized corrugated sheet.

I haven’t had an issue with grain alternations or kept the same as long as the wood is acclimated and prepped right.
I think the problem here is wood that wasn’t dried enough yet and still has a way to go.

View Richard Lee's profile

Richard Lee

185 posts in 948 days


#9 posted 10-22-2018 10:31 PM


Did you alternate the grain pattern ?

If you glued a bunch of 7” wide boards together without alternating the grain its going to cup almost regardless of moisture content.
Yes you will end up with a corrugated panel but it should even itself out.
Yes wet wood will always be a problem.

- Richard Lee

With 7” wide boards alternating won t do much. Each board is wide enough that the cupping will happen to each one. Even with alternating boards, the table will look like an oversized corrugated sheet.

I haven t had an issue with grain alternations or kept the same as long as the wood is acclimated and prepped right.
I think the problem here is wood that wasn t dried enough yet and still has a way to go.

- AZWoody


Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com