All,
I need a bit of guidance from anyone with an idea. here’s the scenario: about 2 months ago, made an extension table for a tablesaw. It is constructed of two 1″ sheets of MDF and laminated on one side. I used contact cement for both the laminate and laminating the two sheets of MDF together. The size of the table (without edge boards) is 23-3/4″ X about 65″ . I flush trimmed the laminate to the MDF. Then, I attached one edge board (2″X1-5/8″X23-3/4″ hard maple) to one of the short edges. I then had to leave town for a while as some of you know. Well, I am home again and started working on it. I had leaned the piece against a wall in my sister’s garage before I left. I get the edge boards for the long sides together and get ready to assemble (gluing with biscuits). I go over to the board and the laminate is larger than the MDF now. All three exposed sides show the same amount of overhanging laminate. The amount is enough that I will need to flush trim again. To top that off, the MDF sheets are not aligned anymore on the other short side (the side that was on top while is was leaning against the wall. It is not as though I was leaning it at a 30 degree angle, the bottom was about 3″ from the wall….
Any clues? Did the MDF shrink that much (about a total of 1/16″)? The MDF was in MY garage for at least a year prior. Laminate was new from Home Depot.
-Del
Replies
Del, you don't say how the one edge with the maple lipping attached has been affected. By your description, this edge was on the floor. It might be worth having a close look there between the edge of the two bits of MDF and the face of the Maple. You've experienced glue creep by the sound of it, contact cement being a renowned creeper because it is always rubbery. It sems likely that if you lean the board the opposite way against the wall, it'll 'creep' back into alignment again, given time. You can replicate this effect by using sash cramps and some imaginative blocking to achieve the same result in a couple or three days.
As to the plastic laminate, many people fail to appreciate how volatile it is: they assume it is stable, as they assume MDF is stable. Neither are entirely, and plastic laminate expands and contracts at a different rate to MDF in the same conditions. Bridges and roads are made with expansion plates to accomodate size changes due to heat, cold, humidity, loading, etc., and even MDF and plastic laminate need some allowance for the same factors. Plastic laminate expands quite a bit under conditions of sustained humidity-- How hot and humid is the garage it was stored in? If you trim the overhang and then use the table top in a fairly dry atmosphere there is a chance that it will shrink back from the edge later. Try putting your top in a dry place for a few days first and see what happens before you trim the laminate.
Of course, you could just place your panel in a dry atmosphere for a few days, leaned up against a wall perhaps, and then trim all the edges a bo'hair to make the whole thing 1/8" to 3/16" smaller. Slainte, RJ.
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