Replies

1. 
   flairwoodworks | Jan 18, 2008 01:49am | #1

   I recently complted a dining room table of dogwood.  I used kiln dried boards 4-6" wide.  I don't particularly like the look of breadboards in the middle of a table top.  At the ends, it's okay.  I opted for battens mounted to the underside of the leafs and tabletop.  I needed them to be flush, so I routed out a cavity and screwed the battens in.  Check out my website for pictures.  http://www.flairwoodwork.spaces.live.com

   Chris @ flairwoodworks

    - 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

1. 
   woodworks | Jan 19, 2008 02:29am | #7

   Chris,

   Thanks for the information as well as the inspiration.  Your table is beautiful .

   Good idea with the battens hollowed out to keep the underside flush. 

   Good Luck on the tool chest

                 Woodworks 

2. 
   mapleman | Jan 18, 2008 04:43am | #2

   woodworks,

   with a little more info I could pin down pretty closely how much your board will move. Knowing how much it will move wll help you decide which construction method is best.

   Is this Honduran or African Mahogany?

   What part of the US do you live (state?)

   Flat sawn or quarter sawn lumber ?(I am assuming flat sawn if it's 32" wide)

   I would highly recommend AGAINST attaching a 32" wide board to mdf or anything else which will restrict expansion/contraction. You will likely need some sort of cleats screwed to the underside of the top with oval/slotted screw holes. The breadboard ends, should you use them, should be attached with a full-length mortise and tenon (or multiple smaller mortise and tenons) but only the center should be glued, allowing the outer edges of the board to expand and contract. The tenon should be on the tabletop itself and the mortise should be cut in the breadboard ends. Note that the breadboard end will not contract at all (or imperceptibly) while the wide mahogany may expand/contract quite a bit, so the breadboard end has the possibility of extending past the top during some parts of the year.

   Hope this helps

   Lee

1. 
   woodworks | Jan 18, 2008 06:43pm | #3

   Mapleman,

   Thanks for your help.   The board is Honduran  Mahogheny- not African.  I live in Northeastern  Ill.  McHenry County. -about 30 mi. south of the Wisconsin line and abour 25 mi. west of Lake Michigan.   The board is flat sawn and already sanded to 3/4 inch thickness. 

   The board is  about 10 feet long ,and I may not use  a breadboard on the ends.  However, I would like the option for design purposes.  Therefore, the amount of movement becomes inportant. 

                                       Thanks for your help.

                                        

    

     

1. 
   mapleman | Jan 18, 2008 07:49pm | #4

   wooworks,

   Using the Lee Valley wood movement reference guide, and assuming you have a MC fluctuation of 4.7 points (figured by avg temps and relative humidity) in your area:

   flat/plainsawn Mahogany (swietenia macrophylla) has a .0024  per inch Chart Movement Value. CMV is the amt of movement per unit of width (inches) per 1% MC change.

   SO,

   32" width X .0024 X 4.7= .36096 inches of movement

   Keep in mind this is the absolute maximum. The chart says this is for unfinished wood - and that wood finished with urethane, paint or varnish will have a much smaller expansion/shrinkage. Make sure you finish both sides of the top equally to help prevent cupping.

    Also, your area may not have that 4.7% swing in MC, but the chart says"as a general rule, the most fluctuation will occur in a climate with a cold winter and a humid summer" it also goes on to say that in Boston, Mass. interior woodwork will experience at least 6% and up to 10% seasonal MC fluctualtion. Florida and the gulf coast states normally have less than 1% MC fluctuation, and the entire west coast of North America from Mexico to the Alaskan panhandle will typically experience a MC fluctuation of between 2 and 4%

   Probably more info than you wanted to know, but hope this helps

   Lee

    

2. 
   HowardAcheson | Jan 18, 2008 11:06pm | #5

   Help me understand what you are planning to do. Is the table going to be a standard pull out table with slides in the center? What direction will the grain run--across the short way or along the long way? Normally, pull out tables have boards that run across the short way. The grain of the leaves runs in the same direction. You would not have a breadboard edge on either the main part of the table nor on the leaves. As has already been said, you can not laminate a solid wood to a composition material substrate without causing real big warping problems.I would suggest you get a good book on building tables. Taunton has a couple I am sure. There are a number or engineering considerations that need to be worked through. In addition, be sure you get some info on dimensions from floor to underside, space per person for chairs and seating, etc.Howie.........

1. 
   woodworks | Jan 19, 2008 01:46am | #6

    The table will be a pull out with one or two leaves.  I am working with a single  large  mahoghany board (approx. 31 " wide and 10' long) that will run lengthwise and form the center of the table.  I will  cut the board in half to form the center panel for each pull out end. I should also have enough material for one or two leaves.  All from the same board with continuous grain run in the center  from one end to the other.  The board is only 3/4 " thick, so I will use a composite panel underneath to strengthen  and support the overall top, and get the desired 1 1/2 " total top thickness.    I agree on the lamination problems, and will probably attach it underneath with slotted screws to accomodate lateral movement of the center board.  I want the total width to be approx. 41" so I intend to glue boards on each side of the center panel.  They will be approx. 1 1/2 thick. which is the dimension I want for the entire perimeter of the top.  Therefore, I am thinking of breadboards on each end.    The expandable  table will be approx. 41 X 66 with a 15" leave, plus and additional 10-12" leave. The legs will be 3" to 3 1/4 diameter- some of which will be turned- and a taper to approx 2-2 1/2 at the bottom.     

   I appreciate your comments -especially the need to look at space for seating, floor to underside, etc.  I am in the process of finalizing the design and will certainly look at those issues.   What engineering factors are critical in your opinion? 

   Thanks for your interest and comments

                               Woodworks

                                        Woodworks

    

1. 
   dherzig | Jan 25, 2008 02:26am | #15

   All of the tables I have seen of that type have the grain running the short way. However, with such a beautiful piece of wood, you might consider not having it open in the middle and preserve the board. Instead you might consider having free-standing extensions that can be added to either end. The other possibility would be to have the table top lifted at either end and have the extensions slide out from underneath (with pull out braces to support them.) I have seen a number of A&C tables made that way as well as some Danish Modern styles.

2. 
   woodworks | Jan 27, 2008 07:09pm | #16

   Thanks for the  ideas on the table design.  I had not considered free standing extensions. Sounds like a good idea, but I can't use it now.   I have already cut the board into the main segments and they are in the basement now.  I have cross braced them and they are stacked to allow for adjusting to the new environment.   I about a month,I plan to begin working  with them. 

                                   Woodworks

3. 
   JeffHeath | Jan 19, 2008 09:30pm | #8

   Chrissakes, where are you at in McHenry county????

   I'm in Crystal Lake.  Come on over to my shop, and I'll show you exactly how to make that table top so that it doesn't blow up on you, and I'll show you a few different ways to attach the top to the base to allow for seasonal movement, which we get plenty of around here.  The construction methods you are describing in your original post will blow up on you.

   The offer stands, let me know.  I'm in my shop every day, but tomorrow I'll be watching football.  You can come early, if you like.

   Jeff

1. 
   woodworks | Jan 20, 2008 12:14am | #9

   Jeff,

   This is scary.  I live in Crystal Lake and would very much like to talk with you.  What is your phone number.  I'll call you on Monday.

                                          Woodworks

                                      Joe  O'Malley

    

1. 
   JeffHeath | Jan 20, 2008 02:12am | #10

   I sent you an email.

   Jeff

3. 
   blewcrowe | Jan 24, 2008 05:36pm | #11

   up to 1" per yard

1. 
   woodworks | Jan 24, 2008 06:14pm | #12

   Thanks for the input.  I will try to design the support system to accomodate the potential for considerable movement.  I intend to finish both sides of the table top to help keep the movement down a bit.

    

                              Woodworks 

1. 
   blewcrowe | Jan 24, 2008 06:35pm | #13

   I wasn't overly clear on that.

   Wood movement varies with species and the way wood has been sawn, etc etc etc.

   But commonly, 3-4% can be the case, which equates to an inch per yard (36").

   Now, keep in mind, that is movement across the whole piece, so if the piece is fixed at the middle point, then you could get up to 1/2" to the left of it and 1/2" to the right of it.

1. 
   saschafer | Jan 24, 2008 06:43pm | #14

   That's true in general, but Honduras mahogany has a very low expansion coefficient, so it would take an extremely large change in moisture content for it to move that much (over 12% delta MC).

   -Steve