Replies

1. 
   jazzdogg | Jun 13, 2006 08:58pm | #1

   I can't tell from your description whether you'll be joining the two species end-to-end, or if one will be perpendicular to the other.

   More info, please,

    

   -Jazzdogg-

   "Don't ask yourself what the world needs. Ask yourself what makes you come alive, and go do that, because what the world needs is people who have come alive." Gil Bailie

2. 
   JohnWW | Jun 13, 2006 09:18pm | #2

   Wood movement probably won't be a problem but that depends on details you haven't supplied.  If you want a more precise answer about the wood movement question, I would have to know the grain orientation of the two woods and the length of the joint. 

   That will be a weak joint structurally, hopefully there will be a support, like aprons, underneath the top to provide strength.  Also, the top will have to be mounted to the understructure in a way that will allow the entire top to expand and contract with humidity changes, otherwise you will still have potential cracking problems.

   John White, Shop Manager, Fine Woodworking Magazine

1. 
   71Atlas | Jun 14, 2006 05:58am | #4

   The board will be a total of 40" long by 10 1/2" wide. The zebrawood will be 30" long by 10 1/2 wide joined on each end with walnut  5" long by 10 1/2" wide. The grain will be all in the same direction along the 40" length, joined end grain to end grain.  I plan on using a total of six #10 biscuits at each joint between the walnut and zebrawood for strength. The ends will be unsupported by 5" on each end. The table is not going to be supporting any heavy loads and will be used mostly for displaying small objects. The expansion that I am concerned about is in the 10 1/2" direction where the walnut and the zebrawood is biscuited together.

1. 
   Rich14 | Jun 15, 2006 01:23am | #7

   71Atlas,

   Whenever I try to discourage someone from using bicuit joints I cringe, because people asking for advice about them seem focused on employing them, no matter what.

   First, I have absolutely no use for them. There are far better ways to mate 2 pieces of wood, under any circumstance. That said, and my bias clearly known:

   Don't use them in this application. They are the wrong solution to the task. You are describing a joint already fraught with problems as, other than the glue area provided by biscuits, you have no long grain to long grain glue surfaces. There is no strength to a wood glue joint without long grain surfaces.

   The way to create your long piece is with a mortise and tenon joint, or second choice a spline joint between the two species. You can hide the joint or leave it visible for visual interest. Either specie could be the mortise or the tenon piece.

   Commercial lumber is joined in this way using finger joints which expands on the M&T joint concept, with increased gluing surface. I've never seen different species mated this way, though.

   The 2 species will move against each other in width with changes in ambient humidity. The movement is inevitable. The relative movement should be very small, nowhere near that which would occur in breadboard construction.

   Rich

   Edited 6/14/2006 6:31 pm ET by Rich14

1. 
   71Atlas | Jun 15, 2006 06:55pm | #9

   Thank you all for your suggestions but since I am always in too much of a hurry, I have glued the pieces together with BISCUITS and hope for the best. I put two biscuits one above the other in the middle and glued them solid. At each end I glued the top biscuit to the one side of the joint and the bottom biscuit I glued it to the other side of the joint. I am hoping that this will give the necessary relief for movement to prevent cracking. I have also chamfered where the joining takes place as suggested. I will report back next year if it works.

1. 
   Rich14 | Jun 15, 2006 08:07pm | #10

   from msg 8

   ". . .Whenever I try to discourage someone from using bicuit joints I cringe, because people asking for advice about them seem focused on employing them, no matter what. . ."

   Let us know.

2. 
   cadiddlehopper | Jun 15, 2006 02:45am | #8

   Doorboy, ring, & rich14 make excellent points & suggestions. There is another approach to construction IF & ONLY IF you must have a perfect joint between zebrano & walnut & that is to use veneer over a one-piece substrate. My guess is that it is too late for that. For solid wood, may I suggest polyurethane glue & M&T joint followed by a very shallow v-groove or other reveal feature dead over the glue joint. Do some clamping along the joint to prevent glue expansion from breaking anything. A discontinuous tenon is a good idea for that purpose, too. Poly glue seems to force itself into end grain as it expands thus filling small gaps nicely. If you use a spline instead of M&T, keep its grain parallel to table top grain.CadiddlehopperCadiddlehopper

3. 
   BruceS | Jun 14, 2006 04:59am | #3

   Are you intending on doing a bread board edge ??  Give us the length and width of both pieces of lumber, and grain orientation.  We'll go from there, thanks.

   Work Safe,  Count to 10 when your done for the day !!

   Bruce S. 

    

4. 
   doorboy | Jun 14, 2006 05:35pm | #5

   It's just an educated guess, but I am pretty sure you WILL have a crack at that joint. End-grain to end-grain joinery is not a good glue application. The biscuits will help, but they will not stop the wood from moving with the seasons. ANY two pieces of wood will move at different rates from one another and even a miniscule amount of movement will create a line--or crack--in the finish.
   That being said, I would go for it since you will not be laying out a major amount of money. Goodluck

   "Kinky for Gov. of Texas"

5. 
   ring | Jun 14, 2006 07:49pm | #6

   You're going to have a very small amount of differential movement.  Not enough to be intimidating, but enough to spoil your enjoyment of the piece if you were expecting a perfect continuity of line.  I would bevel the edges ever so slightly at the butt joint to create a purposeful transition and hide the slight movement that will inevitably appear.  Maybe consider using that slight bevel throughout the piece as a design element.

   DR