A few years ago I made a sof atable out of old barnwood (pine) It ended up just under 3/4 inch thick due to pre-existing cupping and twist of the boards which were about 4/4 rough sawn. I did a breadboard end to keep it flat. I thought I had alternated growth ring direction when glueing up. It was finished with shellac and the breadboard pinned throught he tenon at the center. Over the last 3-4 years the table has cupped so strongly that it actually cracked open the slot in the breadboard! I was surprised since the wood was 75 years old and had presumably dried completely. I f I glue it it will fail again. I had considered ripping it in half, flipping over half to minimize the cup and making new breadboards. I cant really plane it further without making it too thin. Any suggestions? Thanks.
Jay
Replies
Breadboards have only limited affect in minimizing panel warpage. If the panel wants to warp, the breadboard will only provide some resistance to warping at the ends. It will have no affect on the center area of the panel. Alternating end grain growth rings will not prevent warping.
Barnboard is always problematic in regards to stability. How long did you acclimate the wood to your shop or to the environment where you placed it?
Personally, I would remake the tabletop using standard kiln dried wood or barnboard that has be acclimated for 4-6 months before you mill and glue it. Be sure to equal amounts of wood off both sides if you have to joint it or plane it.
What's a breadboard?
I heart Festool
It's a way to finish off end grain -- so named because it's often used on breadboards. You tenon a pice of wood to a, for example, table top, with the grain running perpendicular to the main piece. More decorative than useful for controlling wood movement, IMHO.
Mike HennessyPittsburgh, PA
Mike said it and I think he is right....
I recall Tage Frid did NOT alternate wood grain for tops.. I could be wrong.. What I remember..
I think less stress overall along the length of of the breadboard. However if I make something it is usually plywood with a good wood on top AND sometimes the bottom I like better than th A1 side!
Will,
I just finished reading Tage Frid's Book 1. With quartersawn wood, he was concerned with having heartwood against heartwood and sapwood against sapwood, but makes no mention of grain orientation with flatsawn boards.Chris @ http://www.flairwoodwork.spaces.live.com
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
I am sure you are right!
All my teachers told me I read all sorts of things into what I just read! Maybe it is because when I read something I like I get these visions in my brain.. Somehow I must get MY ideas in the story!
Jay,
You may be able to put a couple of cleats underneath to help pull the warp out then put new bread board ends on. The cleats, if thats the right term for them, would be placed on edge and installed with screws through slotted holes to allow expansion/contraction of the top. Just a thought
Tom
Posts 42346.37 and .38 may give you an option in part, depending how the table was finished. Power Tools etc.
Edited 7/4/2008 7:01 am ET by mufti
How was the top fastened to the legs?
If you had warpage, the moisture content of the wood was not in equilibrium with the surrounding environment. It was either too wet or too dry, probably too wet since old barnwood would be air-dried from long years outside.
Thanks for the comments. The wood (pine) had significant cupping and twist and so after face fointing and planing it ended up on the thin side. (as I said, less than 3/4 inch) Therefore the tenon was 1/4 inch thick and the walls of the mortise in the breadboard were also 1/4 inch thick. Apparently not strong enough to keep the board flat, without failing under the stress. The wood had acclimated in my shop for several months and I was cognizant to plane approximately equal amounts off of each surface, but the pre-existing cupping caused more material to be removed centrally on the convex side and at the edges on the concave side. Could that have caused the glued up panel to cup? Regarding alternating boards' with heartwood up or down,; if you do, you get a tendency for a wave effect (boards cup in opposite directions), and if you don't you get a tendency for an overall cup of the panel (boards cup in the same direction). Pick your poison.
In any case, if I make a new breadboard, it will not be able to flatten the panel. My only hope would be, I think to rip it back into the original 3 boards that were glued up, re-edge joint them and re-glue them into a flat panel. I would then have to sand and re-finish, and hope that there would be no more forces tending to do the same thing again. I could re do a breadboard end of a stronger material such as maple to offset the thin mortise walls. Any other thoughts?
Thanks again,
Jay
Jay,
How does the humidity in your shop compare to that of the table's residence? With the amount of time you let the wood acclimatise, there is no reason for what happened.
Chris @ http://www.flairwoodwork.spaces.live.com
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
Edited 7/6/2008 11:11 pm by flairwoodworks
Should be the same. My shop is inthe basement of my house and both are on the same HVAC system.
Jay
If your wood had significant cupping to begin with, that's the first sign of trouble. Wood expands and contracts perpendicular to the axis of growth. How this movement affects the stick depends on where the wood came from relative to the log, and how it was sawn. Much pine is cut without a lot of attention to how stabile the boards will end up, since it's largely destined for the construction industry where it doesn't matter so much. If the wood is flat sawn from near the center of the log, the unavoidable movement will cause the wood to cup - a lot - as the moisture content changes. Letting the wood acclimatize to your shop, even for years, will do no good unless your shop has constant temp and humidity (mine sure doesn't) and you intend to keep the finished piece in your shop forever after it's built. Probably not what you had in mind. ;-)
One way to reduce the movement is to rip the wide boards into thinner boards and rejoin them, alternating the growth rings so the board gets "wavey" when it moves instead of radically cupping, as you have suggested. This works, sorta, but is, at best, a compromise. Better to use more stabile wood to begin with.
If you are going to build furniture from lumber yard pine, you'll need to learn to select good, furniture-quality stock. (Which may be a fool's errand, depening on your yard and the wood they carry.) A quick and easy way to do this is to reject wood that's cupped or twisted, and to look at the end grain and try to select boards where the growth rings are as close to perpendicular to the surface as possible, i.e., quartersawn. (Even if the sawyer's not trying to quartersaw, a significant percentage of stock from any log is naturally "quartersawn".)
If it wuz me, and it ain't, I'd toss the top, chalk it up to a learning experience, and start anew with some better boards. Otherwise, you'll just be chasing your tail.
I can't cite numbers, but the forces generated by wood as it moves with it's moisture content are pretty large -- much larger than the ability of any breadboard end to contain. Therefore, BB ends, should be considered more decorative than structural. Further, even if the BB ends could keep the top flat, the cupping movement of the wood may well be accomodated by the wood in the top splitting on the convex side.
You will NOT be able to stop the wood from moving. Your only hope is to understand and predict how it will happen and plan for it to allow for the movement to occur in a way that is acceptable to your design.
Mike HennessyPittsburgh, PA
Edited 7/7/2008 7:55 am ET by MikeHennessy
Thanks. I salvaged the boards from a 75 year old chicken house that we had on a farm property beofre it was demolished. The wood has character with worm holes and rusted nail holes. I had to go over it with a metal detector before planing. The fact that it came from our farm had some meaning, and the piece did look rustic. Otherwise, no doubt, there is better quality furniture grade lumber out there.
Jay
Some grain is just going to mean movement no matter what you do -- you can make it flat for a time, but it will keep breathing, and therefore, keep moving. Think of such planks a slow-moving pendulums -- even if you could make the board flat at one end of the swing, there's no way to make it flat at both ends of the swing.
As others have said, breadboards don't do much to prevent anything more than the slightest warping. A few sliding dovetail cleats might help some, but that's a difficult job, and may not work in all designs.
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