I’m looking for a solution to take the twist out and put a table top back to flat. I built a small table using Doug Fir 2″ slabs dried to 6%. These were book matched slabs about 16″ wide and straight lined and than glued together. They were flat and sanded, after the table was completed the twist started. I’m looking for a way if there is one to remove the twist and bring it back to flat. Any ideas?
Edited 11/26/2009 12:44 pm ET by djmcnutt
Replies
The amount of stress that a 2" thick slab creates when it decides to bend (twist, warp, cup, etc) is tremendous. Depending on the amount of the twist, it could literally take hundreds of pounds of force to brign the slab back to flat.
And just as soon as you remove that force, the wood will return to the shape that it has chosen.
Your best bet, IMO, is to use whatever tools and talents you have to flatten one side. You could then run it through a wide planer (maybe a nearby cabinet shop has one???). As an option, after flattening one side, you could shim the underside as you re-install it to the base.
I won't be laughing at the lies when I'm gone,
And I can't question how or when or why when I'm gone;
I can't live proud enough to die when I'm gone,
So I guess I'll have to do it while I'm here. (Phil Ochs)
Douglas fir is a moderately stable wood but any flat sawn 2" thick 16" wide plank will move quite a bit as it gains and loses moisture. Part of your problem may have been that you started with wood at such a low MC, it probably would have gained quite a bit of moisture in most environments. Where do you live and are you sure it was at 6% MC when you started?
Wide flatsawn planks are very sexy but almost always twist or cup with changes in the humidity. If the top wasn't finished as well on the underside as the top surface the warpage would be made worse, but other than keeping the finish equal on both surfaces there isn't anything you can do to keep such heavy planks flat.
Shop Manager for FWW Magazine, 1998 to 2007
How is the table top attached to the base ?
If the top was not allowed to move across its width it may have had no where else to go but twisted and such .As has been said Fir 2" thick can have a mind of it's own and it will move , we need to design with movement in mind .
regards dusty
Out of curiosity, what was the immediately prior history of the pieces. If they were bookmatched, was a wider piece resawn, if so how long were the pieces allowed to stabilize before being worked further? When the pieces were flattened, were the rough pieces twisted? If so, how significantly, and were the pieces allowed to stabilize after initial flattening?
Not trying to nitpick. If flattening was rushed, good results might be possible by starting over. If flattening included time to stabilize, the pieces may include reaction wood and never want to cooperate.
Seasonal cupping might be expected with wide flatsawn pieces, but I'm wondering if twisting should be. Hoping some with more knowledge and experience will address the twisting question.
Well, if it were me, I'd get a couple winding sticks and a #7 jointer and go to town and take it back flat. Since you have 2" top to start sacrifice some thickness to get it flat. I'm afraid thats about it. Now you did not menetion how you finished or how you attached it to the base. If the finish was not equal you could have some action goin on there or if you did not allow for some kind of movement stuff can happen. If you still can remove the top from the base get it back flat and let it sit for a while and refinish and reattach. I had a similar issue with a top I made out of red oak for a chest that was a wide board. I was afraid it being flat sawn (georgous grain pattern), it would get funky and move. I purposly left it thick at 1 1/8" knowing I'd need to take it down. Sure enough after letting the large panel sit it twisted. I used the winding sticks and LN to knock it down to a finished thickness around 7/8". It was not perfectly the same thickness all around but pretty darned close and you can't tell unless you put calipers on it. Finished it carefully both sides and its been ok since. I was scared to death too. It was made in St. Louis and now resides in my nieces house at the eastern shore of md. Wish I had an easy solution to tell you. Good luck.
...Advice is a form of nostalgia. Dispensing it is a way of fishing the past from the disposal, wiping it off , painting over the ugly parts, and recycling it for more than it’s worth – lyrics from the song wear sunscreen
Thank you to everyone for your responses. Just to fill everyone in on the questioned asked. These slabs were sawn from one log and they are the center two slabs. For the most part they would be as close to quarter sawn being from the center of the log. Only the very edge was sawn off of one side to have them book matched, the other edge still has the natural edge on them. The top is bolted to the base and can be removed. It sounds like maybe I should have some kind of slot in the base to allow for movement. I have not not finished the piece because of the problem. I did not want to do this in case I need to rework it. What would everyone think of using a CNC to flatten the top on one side than plain and sand the other to match the flat surface?
Just a wild guess, but how about a series of "kerf-cuts" in the underside of that slab? maybe 1/2 to 3/4 the way through. This would allow the top to be "pulled" flat by those bolts, without a lot of stress to the top itself. " Although I have the right to remain stupid, I try not to abuse that right"
Thank you for your reponce. This was one of my thoughts, except I thought maybe of filling them with epoxy once it was flat to keep it that way.
Do the boards include the center of the log, or close to it so that the rings near the center of each board are very small radius? In either case that would be the source of your warpage.John White
Shop Manager for FWW Magazine, 1998 to 2007
How close to the pith or how small a ring is supposedly safe?
The sawyer I worked with would cut a cant down until about a 4x4 or 5x5 would be left dead center and call it garbage. He used them to start a stack of lumber. He called them wooley boogers just never know how they are going to react. ...Advice is a form of nostalgia. Dispensing it is a way of fishing the past from the disposal, wiping it off , painting over the ugly parts, and recycling it for more than it’s worth – lyrics from the song wear sunscreen
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