Replies

1. 
   BobSmalser | Dec 12, 2003 09:56pm | #1

   I'm having a hard time picturing your "caps"...but neither poly nor aliphatic will glue well over top of old glue.  A good boatbuilder's epoxy like West System does that a bit better and is much more flexible.  I don't like miter joints for the reasons you state...and I always try to spline them...usually with 1/8" or 1/4" plywood scraps.

   “When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.

2. 
   Robin | Dec 12, 2003 10:13pm | #2

   First off I will admit to being a novice - but is there anyway you could use those  little figure-eight things (I'm sure they have a name) that are used to attach a table top so that any movement is allowed without causing a problem??  With the height of your columns you might have to glue up three of the sides, attach the top from underneath, and then glue up the fourth side.  Just a suggestion.

   Of course this might not be an option with the columns you've already made, right, duh???  But maybe for future projects.

   Robin, Molly & Sadie (the Wonder labs!) And yes, it's still football time in Tennessee at least until Jan 3!

   It's football time in Tennessee!  Go Vols!!!!
1. 
   eddiefromAustralia | Dec 13, 2003 03:28pm | #7

   those  little figure-eight things (I'm sure they have a name)

   Table top connectors.

   Cheers,

   eddie

1. 
   BobSmalser | Dec 14, 2003 02:09am | #9

   Buttons in a groove?

   Like these shop-made ones?

   Tabletop Buttons“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.

1. 
   BillCummings | Dec 14, 2003 06:51pm | #10

   Bob, thanks for responding; the buttons would work perfectly except the pedastal is 48" long and only 18" square so I cannot reach the end to screw the buttons on. also my delema is after I put the first end cap on, the box is sealed on all sides so i could not get to the screws for the second end cap.

1. 
   TomMGTC | Dec 14, 2003 10:26pm | #11

   This peice seems like it would be much better suited to plywood construction. It is destined to fail if made from solid wood. Why not make some replacement pedestals from plywood and miter all the joints including the tops and bottoms. No movement issues and no call backs. I would cut my losses and remake them if I wanted to retain the client.Tom

   Douglasville, GA

2. 
   BobSmalser | Dec 15, 2003 01:40am | #12

   Am sure it can be made to work from solid stock...I just need to see some sort of pic or diagram to fugure out what the problem is.“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.

3. 
   BillCummings | Dec 20, 2003 12:51am | #17

   Bob i am working on getting a picture for you to look at. I had some but cannot locate them on my computer may have to go to gallery and take some more.

4. 
   BobSmalser | Dec 20, 2003 01:25am | #18

   The other trick I use when I'm absolutely forced to use the hated miter joint is spline them using a 45 degree jig on the tablesaw and Luan doorskin 1/8" splines.

   That and boatbuilder's epoxy for max flexibility.“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.

5. 
   BillCummings | Dec 20, 2003 01:38am | #19

   Every place I used the lock-miter joint  is just fine and has not moved or split at all. Just the tops split where I did not use a mechanical joint.

6. 
   BillCummings | Dec 20, 2003 12:50am | #16

   Tom, thanks for your thoughts. I rellay cannot afford to replace all 16 pedestals at this time - $$$ and hours - So I have to experiment with replacement top solutions.

3. 
   jackplane | Dec 12, 2003 10:17pm | #3

   Bill,

    I suspect the real problem here is moisture content.I'd bet the mc of lumber in your shop is a good bit higher than in the art gallery where they've been sitting for a year, in a temperature and humidity controlled environment.

     Without seeing pics,maybe you could alter the design of the pedestals to minimize the gaps,or eliminate them with a new veneered top.

1. 
   BillCummings | Dec 12, 2003 11:05pm | #4

   I'm going to try the spacer thing first and then if it still moves will replace the caps with plywood or painted MDF but that will be expensive and all my profit from the job will be down the drain. I should have planned better before the final assembly last year.

4. 
   MikeRooney | Dec 13, 2003 06:17am | #5

   Your problem is wood movement and no glue, no joint is going to stop it. Wood will always move. You need a mechanical solution. Think of the top like a tabletop and sides are like the apron on a table.

   
   

   ---

   Edited 12/12/2003 10:22:36 PM ET by Mike

1. 
   15Broad | Dec 13, 2003 02:30pm | #6

   I agree with Mike and Lab-Girl.  Buttons are probably the way to go, or something like them.  What about a decorative trim rail with slotted screw holes to allow the pieces to move?  I don't know if that would be a feasible solution, as I'm fairly new to this trade, but everybody gets to play, right?

5. 
   eddiefromAustralia | Dec 13, 2003 03:41pm | #8

   Bill,

   I'm having a hard time visualising where the problem is - the way that I understand your description, you've built the lock-mitred pedestal with the top rebated flush into the sides.

   My immediate thought is that the rebate should hold the load, so it shouldn't be glue failure a/c ordinary loads

   Now, is the crack on the endgrain of the top (shrinkage should be approx the same in top and side) or is it between the side grain of the top and the pedestal side (differential shrinkage)?

   Is the pedestal under heavy load (cracking due possibly to deflection), or have the tops cupped away from the sides a/c humidity changes?

   These are a really rough few possible causes that I came up with as I'm typing.

   A bit more info might help others give you some pointers.  As alluded to, it's always better to have a shadowline between two different components to avoid this problem.

   Hindsight's always 20/20, and if you have to redo, I'd look at a barefaced tongue and trench, with the show edges bevelled approx 1/16 and no glue.

   Bear in mind that the differential shrinkage between humid and dry conditions is approx 1% (I don't work with maple, but this is an approx number).  Across 18" width where the top and the sides have grain misalignment (long and cross grain), you will get approx 3/16" difference in width to accommodate.  Hope this makes sense.

   Cheers,

   eddie

6. 
   JohnWW | Dec 15, 2003 02:04am | #13

   Bill,

   Your problem is with wood movement, the sides of your pedestals are expanding and contracting with seasonal changes in the weather, this is totally unavoidable and can not be fixed with a finish. 

   If your case is in a climate like New England (bone dry winters and humid summers) the sides are a full half inch wider in the summer than they are in the winter.  As you've discovered, if a design doesn't take this movement into account something breaks.  Your idea of using a spacer that runs cross grain to the sides will likely result in the sides splitting in the future.

   I'm presuming from your description that the pedestals were meant to look like solid cubes, with seamless sharp corners, no moldings and no overhang of the top.  The only way that design could work would be if the pedestals were made out of plywood or MDF because those materials respond differently to changes in moisture.

   To salvage the existing solid wood pedestals, you need to change the way the tops work.  The simplest solution would be to make new tops that overhang the sides, using one of the techniques commonly used by cabinetmakers to allow the new tops to float. 

   The alternative is to put a ledge inside of the top edge of the pedestal and drop in a new top with enough room around the edges of the top to allow for additinal shrinkage in your area's dry season if it isn't already that time of the year.  Note that the ledge piece can't restrict the movement of the sides, it needs to be vertical grain also or broken into several smaller pieces.

   Hope this helps, there isn't a really simple solution at this point.

   John W.

    

1. 
   MikeRooney | Dec 16, 2003 03:49am | #14

     I'm thinking maybe magnets here."If we're treading on thin ice,

     Then we might as well dance."

2. 
   BillCummings | Dec 20, 2003 12:45am | #15

   John, thanks for your ideas, the next set I do will be plywood - I cannot afford to replace all 16 pedestals with a new set of plywood ones. The floating top seems like a good idea - gotta think about how to do that tho. I will dig up some pictures and post then here but you seem to understand exactly what I tried to do. All the sides on the existing set are lock mitered and have not split at all - just the tops and bottoms. Since they are in an climat controlled art gallery I though movement would not be a problem. More when I get some pictures to post.

3. 
   BillCummings | Dec 21, 2003 07:33pm | #20

   John I am leaning toward your solution of putting a series of wood brackets inside and screwing the top through holes in the top that will be plugged after. I will use four or six screws or eight if the four do not seem to hold. I will make the support brackets small so it does not restrict the sides from moving. I will also elongate the holes through the top to allow small movement in the top.

   I have attached a photo of the pedestal with a test top installed. The test top has a spacer between the top and the sides, but I will not be using this method because it will restrict the movement of the sides. I cannot glue the top to the sides.