by tonyj » Mon Dec 31, 2007 3:21 am
Not hard at all.
The template is from a cheapo harbor freight dovetail jig. I used epoxy, but Titebond might work just as well (and dry a little faster, too). No tape needed. The joint is very strong without it.
The first critical step is in matching the ends. You will stack and cut both pieces at the same time. Sandwich the two sheets so the good sides are either placed together or on the outsides. Some people offset one sheet by one-half the measure of the width of one of the fingers on the template, but I didn't and don't think it is necessary.EDIT: You may have to offset the top and bottom sheet by 1/2 the width of the finger. The best way to determine this is to trace the template across the width of the sheet to make sure you don't have a full matching width finger on each side. Then adjust the start point to make sure you have a valley on the other side of the sheet that corresponds to the first finger .
This is one of two critical steps. Place a straight edge across the sheets equal to the depth of the template and clamp in place so the temple finger tips are at the end of the sheets. (The first photo shows the straightedge pulled back from the template--the template should ride along the straightedge). Check this measurement by sliding the template from one side to the other and making sure the tips of the fingers of the template are exactly on the edge all the way across.
Clamp the template so that a full finger is at the edge. Using a router with a flush cut bit with bearing, cut the fingers to the end of the temple, or as far as your clamps will allow. This is the next critical step--move the template and re-clamp making sure to overlap one or two previously cut fingers to make sure the alignment of the template is correct. Repeat this procedure across the sheet until all the fingers are cut. The whole process can be done in about 5 to 10 minutes.
When finished, do not--repeat--do not dry fit the pieces as the joint will be tight and trying to take the dry fitted joint apart will most likely break fingers or damage the ply. Using a brush, coat the finger edges with glue and fit the sheets together. Use a mallet or a hammer and board to fit the fingers together. Let the glue dry and you are done. You can actually move the piece around before the glue has dried, but why rush it.
The pros to this joint--it is fast and strong. You really don't even need any backing battens or framing behind it. The cons are the possibility of misaligning the fingers in which case pieces cannot be put together at all. But I had success on my first and second try.
The biggest pro for this joint--if it is left visible, all your friends and neighbors will think you are some kind of wood joint craftsman! You don't have to admit it was not that hard. Another benefit, as you can see from the second photo, I was able to change the orientation of the ply to get the bendy side on the ply on the front radius of my tear in that 4 foot section. That piece was the outer layer for my top and went from the bottom front to the hatch hinge.
Last edited by
tonyj on Thu Jan 03, 2008 3:40 pm, edited 1 time in total.
Still graced with two eyes and ten fingers (due in no small part to luck!).
Just when you think a problem is solved, an uglier result replaces it.
tony
What is the best way to put plywood together whether I use 1/2 plywood or smaller?
to your work surface.
