I am making a dining room table from air dried, flat sawn red oak now in late April, in western Pennsylvania. My house does not have air conditioning in the summer and I sometimes run a dehumidifier in the spring and summer as the house can feel damp at times. Winter has both electric baseboard and fireplace used often. Moisture content of the same oak wood now in my shop is 3-5%. Any idea about now much longer, or shorter than the table top my bread board ends should be to allow for wood movement over the coarse of a year?
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Where?
Do a web search for "calculate seasonal wood movement". You will find several sites that explain how to calculate it. Knowing the type of wood and the expected seasonal changes in temperature and humidity it will be exposed to, you can determine the max and min dimensions of your table top.
I think Mike Pekovich had something about BB ends. I did a draw leaf table with extensions and BB ends. Not totally happy with the result, some ends do not look good.
Centef pin them at a flush fit for the dry season for a conditioned home. With a/c and heat there is not a ton af variation. I prefer the look of the ends being slightly short sometimes than poking out long and being a "snag hazard".
The "snag hazard" was my first concern. Heat and humidity varies in my home and am expecting some movement. I'm thinking of making them about 1/8" short now to allow for shrinking in the winter.
I made a 15" wide end table out of flat sawn oak with breadboard ends. Air dried. In an un-air conditioned house in southern Tennessee. The breadboard ends were flush in the middle of the humid summer, and projected about 1/8" on each end in the dry winter.
Here air dried gets wood down to around 15% MC. My shop, with a dehumidifier, tends to hold wood at around 10%-11%. My house is probably drier now with summer dehumidification. If your house is humid as outdoors in the summer, make the ends flush or somewhat shorter than the width of the top, as the top will shrink in the winter. If dry in the summer as well as the winter, you will need to calculate the amount of average shrinkage and shorten the ends to match. There will still be seasonal movement, but a lot less.
Green and Green design elements included breadboard ends that were longer than the width of the table with ebony 'keys' that connected the breadboard to the edge boards of the table top. This provided for an aesthetically pleasing transition from the protruding breadboard to the outer sides of the table. It's another way to deal with and accept the seasonal variation.
Thank you! How are the G&G keys attached? Are they attached to both the table top and bb end?
When I made G&G type keys, we used either a table top mortiser or a biscuit jointer followed by a chisel. This was 20+ years ago. We placed glue in one end let the other float. Has held up just fine. If I recall, one was so tight when we test fit, we just left it in without glue and relied on the friction fit. 20+ years later and that looks fine as well.
If you are building quality furniture intended to last many years, you should not design it for climate controlled conditions. You never know where a piece might go sometime in the future. What if a future owner (one of your kids?) has to move and the piece ends up either on a truck or in a non-climate controlled storage unit. This could be enough to do some serious damage if not accommodated during design and construction.
If you are building a breadboard end just because you like the look, what you are doing is fine. Personally, I would avoid the complexity and build the table without a breadboard. Just polish and finish the end grain and leave it exposed.
You mentioned : Moisture content of the same oak wood now in my shop is 3-5%…. I would verify that again since air dried wood rarely gets under 12% until it is built into furniture and spends many years in a climate controlled environment, let alone in a non climatised house it will remain at 12 % and drop in the winter as the heat lowers the relative humidity of the cold air that enters through the cracks. To be under 5% would mean that the lumber has spent a long time in a heated place where the relative humidity was below 20%, quite unlikely in the North Est. This is an important information as it is the starting point from which to calculate wood movement.
In my experience, even kiln dried seldom gets that low. Mine is usually 8-12%
Lived there, worked there,well WVa, and summertime oak projects ,and oak in particular because it is so reactive to humid conditions ,I would avoid if possible. If not possible my solution to the problem of working in high humidity conditions was to crank up the heat. No AC no dehumidifier, 1970s and a woodstove to boot--just hot sweaty weather. If you increase the temperature in your work space you lower the humidity. Not particularly pleasant working at 100+ temperatures but you do what you have to do.
I don't see any wood work being done that is particularly better than woodworking from, oh maybe, 1750. I'm sure work continued year round for them if for no other reason than they ate year round. I would make my ends the width of the table as assembled .The idea is that they do move,or rather the top moves as the wood expands or contracts. The fact that the ends will sometimes be a bit short or long is just part of it. If your wood is stored in some over dry conditions I would try and get it to equalize to maybe something like 12% before I worked with it.
What you're looking for is called the dimensional change coefficient, in this case tangential, which for oak is ~.oo37. The formula is width x expected change in moisture content (from 7% to 14%, so use the full 7) x coefficient. So if your table is 24 inches wide, you'd have 24" x 7 x .0037 = .62"
If your 5% moisture reading is correct, and gets much past 60% RH in your home during the warm seasons, you should expect a *minimum* of 5/8" inch expansion over 2 feet.
I agree with dps13....I have used this formula very successfully.
Here in Maine the MC of my shop varies from 7% in February to 12-13% in July.
I let my wood acclimate for 1-2 weeks before taking it to rough dimensions. I then leave it an additional week before I take it to finish dimensions.
If the table top is red oak flat sawn and 36" wide then my table top will increase by .45" from February to July
Now, how long to make the bread board end? Most will recommend you make them equal the max anticipated expansion. In other words, if I make the top in February, I would make the ends 1/2" longer. If it is July, then I make them equal.
Have fun!!
Breadboard ends on table and desk tops serve many purposes, some functional and some decorative. In all events, if you want to use them then several aspects can be considered and perhaps used to make the breadboard ends fit for purpose.
As another poster mentions, the transition of the breadboard end to the table or desk top can be eased with the use of some form of plug, which also disguises any tongue & groove joinery that would otherwise be exposed.
But whatever design approach is used, it's best to give the breadboard end more than sufficient extension beyond the table edges to deal with even an extreme swelling of the tabletop from a very humid surrounding. Breadboard ends that become shorter than the table top end look not just ugly but very cack-handed.
It's essential, then, to accurately measure the true moisture content of the wood when making the piece. (3-5% moisture content seems very unlikely unless you live in a bone dry desert). You should also assume a moisture content of the surrounding location that can drive the wood moisture content up to as high as 15 - 17%. Damp underground cellars are notorious for producing this effect.
Here are some photos of various breadboard ends in the furniture I've made. There are plenty of additional approaches to making the transition from BB ends to table top. Breadboard ends can be treated as both a decoration and as a functional addition. For example, shaped and protruding breadboards can add a certain definition to a piece; breadboard ends slightly taller than the desktop can serve as stoppers to help prevent things sliding off the desk.
Lataxe
Thank you for your reply. I found the Gary Rogowski article on the Greene and Greene breadboard end and am going to try that. Thanks too for including photos in your reply.