Replies

1. 
   BG | Dec 09, 2009 01:34pm | #1

   essdog,

   I'm going to take a stab at this, maybe others have better advise.

   The real question your asking is 'does my 20"wide by 7/8" thick panel require additional support to prevent warping'. Breadboards, cleats or maybe the apron that it will attach to may be adequate. The key to deciding how much additional support may be required is a function of the wood cut; flatsawn, quartersawn, radial...with flatsawn having the highest propensity to curl as the MC changes.

   All that aside, I like breadboards on coffee tables, easier on the shins.

2. 
   MikeHennessy | Dec 09, 2009 02:18pm | #2

   Purely a question of esthetics. Your call.

   Mike Hennessy
   Pittsburgh, PA
   Everything fits, until you put glue on it.

3. 
   Lataxe | Dec 09, 2009 03:46pm | #3

   Shawn,

   Quite a lot of my tops have BB ends, whether they needs 'em or not!

   And that's the real nub of the matter, as the traditional explanation for the use of BB ends is to prevent a large panel (often made of glued-together boards) from warping as the boards cup because of moisture changes.  But many (including me) also use them purely as a design-element.

   Cupping boards are most likely if flatsawn (sometimes called through & through-cut) boards are used.  When a top is made of such boards that do not alternate their ring-curve direction (between up-facing and down-facing) the tendency to cup will be even greater.

   If you use quarter-sawn boards for the top, there is much less tendency for it to cup across it's width when there are moisture changes.

   So, wide tops made of flatsawn boards that do not alternate ring-direction will have the greatest propensity to warp.  BB ends are then most appropriate as one countermeasure to control the potential warping.

   But as others have pointed out, securing the top (with buttons or other clasp-mechanisms) to the underlying aprons, cabinet carcass or whatever, also serves to control the warping.  A 1" thick top will be held flat by attachment to a substantial underframe.  Only if the underframe is itself thin or flexible will a warping top pull it out of shape instead.

   So, BB ends are often a belt&braces to top-warp prevention, which is mostly provided by firmly attaching that top to the underlying structure.  However, the thicker a top with an inbuilt propensity to warp (one made of flatsawn boards etc) the more contribution will a similarly thick BB end have in helping to counteract the warp-force.

   When the BB end is a significant contributor to anti-warp, it will have most effect if the BB end timber is itself straight and not prone to warp - in particular, free from a tendency to bow in the same dimension as the top might cup.  Making the tongue&groove joining BB end to top quite deep will also help (but make sure potential wood movement differentials between the two are catered for).

   If the aesthetics of the piece allow, using BB ends that are thicker than the top will also make them stiffer and therefore more able to counteract top-warp.  You often see this style in Greene & Greene pieces, for example.

   ****

   But all that being said, I find I often use BB ends where they are not needed for anti-warp purposes but instead provide a better aesthetic.  Some pieces do not look "right" if the top-edges reveal long lengths of end-grain.  It depends on the design-style but also on the timber-type.

   Lataxe

    

1. 
   essdog | Dec 09, 2009 08:08pm | #4

   Thanks Lataxe and others,

   Very good explanation.  I think I'll go with the breadboard ends unless I happen to find quartersawn walnut at the local dealer.  I think flush breadboard ends will be better.... but I'll do the thicker ends as you suggest on my next arts and crafts table.

   thanks!

    

   shawn

4. 
   DonStephan | Dec 10, 2009 04:19am | #5

   Like the more learned contributors before me, I find breadboard ends very attractive.  One point to keep in mind is that the ends of the breadboard ends will often not match up with the width of the table field.  The WIDTH of the field will expand and contract with humidity changes, the LENGTH of the breadboard ends will not change.  It's a minor point unless the table will have a very formal look otherwise.  Trick is to guess where in the annual humidity swing the wood is when the top is constructed, to know how long to make the breadboard ends in relation to the width of the field at that particular time.
   Applying equal coats of finish to top and bottom of the field of the top will minimize its changes in width.

1. 
   Lataxe | Dec 10, 2009 02:40pm | #6

   Don,

   Ah yes - the pulsing width of large tabetops.......  in fact, there are all sorts of little snippets about BB ends that are important. 

   BB ends do need to be longer than the table is wide, as you describe.  With a 3 foot wide top I generally add 1/8" minimum to the each end of the BB ends (1/4" in all).  Even this defeated me with a certain pitch pine table.  It went into a cellar which had a high humidity level.  The tabltop width expanded beyond the BB ends and I had to do a bit of careful top-edge planing to make the thing right.

   Attachment of the BB ends must be carefully done.  It is easy to glue and pin too much tongue to groove.  Happily that cellar table was glued/pinned in only the central 4 inches of the joint, as otherwise there might have been a crack opened up in the top.  Even an unglued tonge&groove joint can be be so tight it jams and causes a top-crack rather than sliding the tongue agin the groove.  I usually wax the unglued portions of the BB end T&G joint to help it slide.

   I like to pin through the BBend's T&G joint but, again, the outlying pins need to have slots in the tongue to allow the T&G joint to slide if it needs to.

   Finally, the edges of the BB end and the top, where they meet, need to be well made and without gaps or raggy edges (all too easy to make on the end-grain of the top's edge) as otherwise the join looks naff.  I find it helps to put a very slight bow in the BB end's edges so that they have to be cramped up to the top to close the resultant small gap in the middle - at the same place where the two will be glued together.  This helps to ensure that there will be no gap open up along the whole BB end/tabletop joint.  Along a 3 foot BB end/top joint, a dip of about 1/16" in the middle is usually enough.

   Lataxe