Replies

1. 
   Alan | Aug 11, 2004 01:45am | #1

   Crhis,

   If I understand you correctly, you want to make a table with a frame running around all four sides so it's like a frame around a picture.  If that's what you're doing:

   There certainly is a way to keep the corners of the frame together as the center changes dimensions with the weather: it's called "frame and panel" construction.  It's the same way paneled doors are made; and it's simple as pie.

   The idea is to run a groove around the inside of all four of the frame pieces.  The inside part, the panel, is made with a tongue running around all four edges that fits into the groove in the frame.

   In your design you will need to figure out the maximum amount your table "panel" may expand and contract, and then make things the right dimensions.  If you can expect a great deal of movement, on the long grain sides you'll need to make the groove deeper, the tongue longer, and the panel fit looser when it's at its driest.  Perhaps others will have some general rules about how much space you should allow for wood movement.

   The only drawback is that during the dry part of the year you may have a little space between the edge of the panel and the frame where crumbs can hide.

   Alan

2. 
   CharlieP | Aug 11, 2004 07:22am | #2

   I suspect the look you are seeking is best done with a "breadboard end."  A board is installed across the end of the table top, but the primary boards go all the way to the side, rather than having a frame on the side as you described. 

   The trick is that wood does not expand and contract materially in length, but the width will change by a few percent with changes in the weather.  Therefore the board(s) on the end(s) must allow the attached wood to slide.  This means that the end board is aligned with a groove for the table top, but is only firmly attached at one point - typically in the center of the table top.  At max expansion the table will be slightly wider than the end board.  At the dry season, the table will be slightly narrower than the end board. 

   There are lots of details that you might consider for a breadboard end, but if you look up that topic, you should find plenty of instructions. 

   Alan's answer is correct for the question you asked, but has the disadvantage of leaving a crack to accumulate table grunge during the dry season.

   You should consider whether you really want to use relatively soft pine for a table top.  There are numerous other things you can do with pine that don't take the abuse usually given table tops. 

   ________________________
   Charlie Plesums  Austin, Texas
   http://www.plesums.com/wood

1. 
   cashbyvt | Aug 11, 2004 02:31pm | #3

   Thanks for the help. I thought about a bread board end but didn't like the way the board is either long or short depending on the weather, but I think that's what I am going to end up doing. The floating panel idea would work, although I don't know how to calculate the expansion, I really don't want a gap. As for using the pine. It is from our house and has some sentimental value. It will be a dining room table and not see everyday use, so it should be okay. It already is pretty worn, the floors were at least fifty or sixty years old if not significantly older, so any dining damage will fit right in with the character of the boards.

   Thanks again.

   Chris

1. 
   CharlieP | Aug 11, 2004 04:25pm | #4

   The amount that the breadboard end would be too long or too short is the amount that the table top will expand/contract.  That is the amount of space that you would have to leave for expansion and contraction in a floating panel - and is the size of the gap. 

   Since plywood isn't subject to that expansion/contraction (the structure forces the expansion into an impreceptible change of thickness rather than width), if you see something that is fully framed, you know it is plywood or similar rather than real wood. ________________________Charlie Plesums  Austin, Texashttp://www.plesums.com/wood

1. 
   SgianDubh | Aug 12, 2004 09:33am | #6

   Charlie, you said, "if you see something that is fully framed, you know it is plywood or similar rather than real wood." 

   Indeed, nowadays that's what you'd expect. But it's remarkable that I sometimes see new solid wood panels with mitred framing tightly enclosing them.

   Just a couple of months ago I acted as a consultant  in a case where exactly this construction had been undertaken. About 12- 14 large dining tables were commissioned at great expense, custom made out of european white oak and installed in the summer of 2003.

   Every one was failing and splitting both along the length and at the frame mitres due to the designer/makers choice of construction technique. My report detailed all sorts of stuff relating to allowing for expansion and contraction and possible remedies. 

   The only permanent remedy I could think of was to scrap all the existing tops and remake them using a technique that allows for the inevitable wood movement. My guesstimate for complete remaking of all the tops was probably a minimum in the region of £10,000+ or ~US$18,000+

   I have no idea what steps have been taken to resolve the problem. It would be a huge financial strain on the small business that made the tables to replace all the faulty tops at no charge to the customer. Slainte.RJFurniture

2. 
   AlanTurner | Aug 11, 2004 05:19pm | #5

   The expansion is easy to figure.

   http://www.woodbin.com/calcs/shrinkulator.htm

   In Philadelphia, I usually use a range of 6% to 11%, to be on the safe side. I don't know what part of the country you live in, so it may vary.

   I used to do the calculation by hand, from Hoadley's Understanding Wood, but the shrinkulator has the math already inbedded in the program, so it is fast and easy.

   There is also a sagulator, which is also handy.Alan

   http://www.alanturnerfurnituremaker.com