Replies

1. 
   ring | Mar 03, 2007 08:54am | #1

   When you say "apron at each end" it suggests to me that you're making a trestle style table, and that there's no apron along the sides, right?  The table base must be perfectly solid without relying on the top at all.  You must use some attachment that will allow for expansion-contraction of the oak top across-grain.  The simplest means are cleats of steel or wood.  Fancier attachments involve sliding dovetails, etc.

   David Ring

   http://www.touchwood.co.il/?id=1&lang=e

2. 
   Lataxe | Mar 03, 2007 04:37pm | #2

   .....or do you mean that the table top will have breadboard ends? 

   The same principle applies - the main table planks will expand and contract across their grain (with humidity changes) by 2 - 2.5 X compared to the expansion/contraction in length of the long grain of the breadboards, so you must allow for the relative movement.

   There are several method but all see the BBs glued to the top only in the centre 3-4 inches with some form of moveable mechanical fastening towards the table edges. 

   Personally I like to make a tongue on the table end, a groove to match in the BB and use slotted holes in the tongue to match round holes in the grooved part of the BBs.  Dowels put through both hold the BB to the table top but allow one to slide sideways agin the other, with the glued bit at the centre staying still and the ends moving in or out, relative to each other.

   The above is the most usual method but there are others......

   Lataxe

1. 
   PBH | Mar 03, 2007 06:32pm | #3

   Thank you.  This is precisely the question (breadboard end), and sounds like the answer I needed.  Very helpful.

   Someone suggested also sealing the ends of the lengthwise boards to retard moisture.  Any point in that?

1. 
   Dano | Mar 03, 2007 07:21pm | #4

   Well, since you state that you are using quarter sawn stock for the top you've pretty much negated any wood movement issues, sealing the ends would be pointless...

   Dano"Form and Function are One" - Frank Lloyd Wright

2. 
   JeffHeath | Mar 03, 2007 08:58pm | #5

   Quartersawn wood will still move, although not as much as flatsawn.  By abiding by joinery techniques that allow for this movement, you will find that problems with your work will not occur. 

   When you attach the table top to whatever leg system you're using, you will also need to allow for seasonal movement of the table, via a fastening system, or elongated screw holes, etc.....

   Jeff

3. 
   Lataxe | Mar 04, 2007 02:56pm | #6

   P,

   There's little point in hoping the sealing of the table top ends will retard longer term moisture changes to any useful degree.  Generally this is done to planks that are being dried, to even out moisture loss from the ends with that of the rest of the planks (end grain dries quicker than long grain because the end grain cuts across the water-transporting "pipes" of the wood).  You have to slap on quite a thick coat of impermeable goo, such as latex-based paint.

   The planks still dry out and shrink.

   In the longer term, the wood of the table top will gain and lose moisture along with changes in the humidity of the air in which it resides.  It cannot be stopped although some finishes are said to slow the process down. 

   If it's covered with a breadboard end, the end grain of the table top is likely to gain/lose moisture to/from the surroundings at a similar rate to the long grain.

   When BBs are not used, it is accepted practice to create a slight gap in the middle of the boards being joined to form the table top.  This causes a slight "crushing" effect at the board ends, when the planks are glued up.  When the table top subsequently loses a bit of moisture, the end grain will lose it faster than the long grain.  Without the gap/crushed-ends technique, you often see tiny gaps open up on at the table ends.  With the gap/crush, these gaps do not usually appear.

   I can verify this from personal experience.  I own a large solid oak table (not made by me) with no BBs and in which no gap/crush technique was used. It has small gaps in the ends, from having been put in a hot conservatory at one time, where the wood dried out a bit and the gaps appeared.  The ends had dried faster than the middle.

   None of my table tops that are sans-BBs (but have gap/crush) have suffered this fate, despite (in one case) going from a relatively damp cellar room to another rather dry conservatory.

   Lataxe

   Edited 3/4/2007 6:59 am ET by Lataxe

1. 
   PBH | Mar 05, 2007 09:23am | #7

   Lataxe

   I really appreciate your advice.  Thank you. 

   I had not heard of the "gap/crushed-ends technique".  Since this will be a dining table, I would hope that the 'gap" wouldn't permit utensils from falling thru!!  Fortunately, mine will have the breadboard ends so I needn't worry.

   Any thoughts about the fundamental difference between red and white oak...same thickness, both quarter sawn?  Any price difference is irrelevant.

   Thanks

   paul

    

1. 
   Lataxe | Mar 05, 2007 05:22pm | #8

   Paul,

   Them gaps is tiny ones - created usually by swooshing a plane or a belt sander over the middle sections of the planks'edges until daylight around 0.5mm wide (exact amount depends on the plank lengths) appears in the middle (none at the ends) when the planks are stood up edge-to-edge.

   White oak is a pleasant enough and hard-wearing wood- also durable.  I never used red oak but it is said to be rather more coarse and isn't durable.  Still, dining tables rarely rot, unless the beetle lives in your house or it is very damp. (I often slobber on our dining table, I confess - its the ladywife's delicious viands wot causes it; also I am reaching dribbling age).  :-)

   I have found white oak prone to splitting more easily than European oak.  I once made a white oak coffee table, all with proper movable joinery and buttons to attach the top, but the cursed thing decided to develop a split in the top anyway.  It almost seems to want to rive itself - nothing in this coffee table had moved anyway, as the humidity in our house changes very little. 

   Has anyone else noticed white oak's propensity to split, I wonder?

   Lataxe

2. 
   Dano | Mar 07, 2007 06:46am | #9

   Paul,

   The so called "gap/crush techique" is more commonly referred to as a sprung joint, which is probably why you haven't heard of it....So don't feel bad, I've got nearly a half century under my belt doing this , first I've heard "gap/crush technique" too.

   Red Oak is more open grained than White, less dense, you will not get the rays and flecks with quarter sawn Red Oak either,  and it doesn't have near the amount of tanin which makes it totally unsuitable as an "exterior" wood....FWIW.

   Dano"Form and Function are One" - Frank Lloyd Wright

3. 
   PBH | Mar 07, 2007 06:59am | #10

   Thanks Dano

   I'm blown away by all the helpfull comments from folks like you.  I may have nore questions in the future.

    

   Paul