Replies

1. 
   mrbird90 | Dec 08, 2004 08:58pm | #1

   Burt, regardless of size, all table tops will shrink and grow with humidity. On small tables I use corner brackets and drill a hole about 1/16" larger in diameter than the screw shank. This allows for dimensional change in the top. On larger tables I use a slot in the aprons and use a floating piece of wood to retain the top. One part of the wood cleat is screwed to the top and the other end floats in a slot in the apron. Also you can buy special metal clips which do the same. But be sure  to allow for shrinkage and expansion on all tops. A plywood top has less movement and is not so sensitive to movement.

2. 
   douglas2cats | Dec 08, 2004 10:25pm | #2

   Burt. Here's an example of what can happen when you don't factor in wood movement. I'm almost too embarrassed to fess up to this but it happened about 25 yrs ago when I was just starting WW and didn't know any better. I'd rather have someone else learn from my mistake.

   Someone gave me an oak table (w/ 2 pullout extension leaves) and chair set because they had spilled something on the top causing some very large dark stains. The staining went very deep and no amount of stripping or sanding could get past the stains. It wasn't an especially nice table and knowing I was interested in WW, they gave it to me as I thought maybe it could be salvaged.

   I didn't yet own a benchtop planer - and the 2 main halves wouldn't have fit anyway -but I did have a hand power planer, so I preceded to start taking off about 1/64" at a time across the tabletop trying to get past the stains. Just to keep things consistent, I did the extension leaves at the same time even though they weren't stained. I finally succeeded then cleaned things up with belt/disc/hand sanding but had to remove almost a 1/4". This left a top thichness of 1/2" which seemed way too thin and likely to sag under use.

   Here's where things started to go wrong. I rationalized that if I attached a 1/4" layer of something on the undersize and then added an edge-banding so that the sandwich wasn't visible I'd be all set. So I proceeded to put a layer of 1/4" Oak plywood underneath and glued it on with Titebond. I then firmly glued on a 3/4 x 3/4 Walnut banding (yup - no breadboard ends here either). I got everything refinished, patted myself on the back, and set up the table in my finished basement. This was around the end of July - very humid in Michigan.

   Now the weather starts turning cold, the furnace starts running regularly, and the humidity in the house gets increasingly dryer. Around September/October the table starts talking to me. Not enough to really get my attention or even to distinguish it from the pops and grunts coming from the house settling, but that table was getting real chatty. The 1/2" original oak was trying to shrink across the grain and the much more stable 1/4" ply and the walnut banding didn't want to go along for the ride.  By November I was hearing pops loud enough to finally realize where they were coming from. But close inspection of the table didn't reveal any problems - not that I could have done much about it at this point anyway. One Saturday morning, I'm drinking my coffee sitting about 20 ft from the table. All of a sudden it sounded like someone had set off an M80 firecracker in the house. I jumped up (spilling hot coffee all over myself in the process) and after realizing where the sound had come from, went over to check out the table. Here were 2 very large cracks - as wide as 1/16" in places - running almost completely across the table, where the top had finally surrendered to my ignorance.

   Moral of the story: Wood wants to expand & contract with humidity. The biggest change is across the grain. There's some miniscule movement length and thickness-wise too, but cross-grain is the one you've really got to worry about. If you lock your tops into position on the base, the top can't move across it's width.

    

1. 
   BBob | Dec 08, 2004 11:28pm | #3

   Well, this brings up another point. All of the tables will be made from salvaged fence wood. The widest I can get is about 5", maybe 6" or a very few select boards. I was planning on gluing the narrow boards to make wider boards and in some instances where the boards are very thin, making sandwiches.So, now it looks like I have 2 problems. What would you have done differently today with your 1/2" oak? I know that I will end up with a lot of 1/2" boards. Is it OK to sandwich them if they are from the same board, or "lot?"Thanks,
   Burt

1. 
   CharlieP | Dec 09, 2004 05:44am | #9

   In answer to the part about gluing up several boards to make a thicker or wider set, it should be no problem if you keep the grain going the same way.  No cross boards for support - they will cause the problem.  Almost all of the expansion and contraction is across the grain, and if the adjacent board is similar, no problem. 

   All the material should be stored together until it is "acclimated" before any processing.  ________________________Charlie Plesums  Austin, Texashttp://www.plesums.com/wood

2. 
   douglas2cats | Dec 09, 2004 03:44pm | #10

   "I know that I will end up with a lot of 1/2" boards. Is it OK to sandwich them if they are from the same board, or "lot?"

   Charlie pretty much answered this, but now you've got to ask yourself 'Do I care if the seam and glueline are visible from the edge?' If you do, just be careful how you cover the edge. Gluing a solid strip of the same stock (or even a contrasting wood) on the edges running with the grain is OK. When you tackle the edges that run across the grain, you need to use something like a breadboard end or sliding dovetail end so that the top can still move.

   "What would you have done differently today with your 1/2" oak? "

   If I did it over again today, I would keep the 1/2" oak for another project and build a new top and extensions. Realistically it would be less work anyway. Since I don't have more of the same-board stock available, even trying to glue on a 1/4" layer of the same species (Red Oak) is slightly risky - although nowhere near as stupid as my plywood fiasco.

    

   Here's another top fastener option for you -  depending on what tools you already have. This type needs a slot cut with either a biscuit jointer, router w/ slot cutter, or table-saw blade raised slowly up into a clamped down board. I've used these on quite a few tables about the size you're doing and they work well.

   http://www.vandykes.com/product/02367325/

    

3. 
   budreaux | Dec 08, 2004 11:39pm | #4

   I have used once and seen many uses of a small figure 8 metal washer to attach the table top.  It allows movement.  Got mine from Woodcraft.

4. 
   BobDallas05 | Dec 09, 2004 12:01am | #5

   I was taught to use the technique described by Mel. Make at least four "L" shaped wood pieces, about 1 1/2 inch wide and 3/4 inch thick, 3 inches long. The long side of the "L" is the length of the piece. Cut a tenon 3/8 inch thick and about 1 inch long to make the "L". Then, cut a 3/8 mortise in the apron, about 3/8 inch from the top to match your tenon. Put the tenon into the mortise and screw the "L" to the table top. You don't want the tenon to go to the bottom of the mortise to permit movement.

5. 
   Pondfish | Dec 09, 2004 12:29am | #6

   My vote for easiest and works is the figure 8 clips from Woodcraft.  Good hardware, all you need is a drill press and Forstner bits for drilling a nice hole on the table skirt.

   Paul

1. 
   dlaporte | Dec 09, 2004 01:10am | #7

   If you are not concerned with authentic reproductions, figure 8 fasteners accomplish a secure top while still allowing all the expansion you want.

1. 
   Pondfish | Dec 09, 2004 02:26am | #8

   Stickley used figure 8 fasteners, so even for authentic reproductions (of A/C furniture), they're OK.  Stickley probably did not buy his on-line from Woodcraft, most likely....