I have some 2 inch square pieces of hard maple into which I'm cutting
1/2 inch wide by 2 inch long through mortises. These pieces make up
a base for a workbench top. For added strength I'm planning to wedge
the tenons, which is something I've heard about but never done.
My understanding is that I need to taper the mortise so that it is
wider on the "outside" side of the stock -- something like 1/8 inch
wider per inch of thickness, so that's 1/4 inch wider for my 2 inch
stock. Therefore the "inside" length of my mortise will be 2 inches
while the "outside" length of it will be 2+1/2 (1/4 wider on both
sides). Then I can either:
a) drive my wedges between the inside of the mortise and the outside
of the tenon (on both sides), sort of squeezing the tenon; or
b) cut two kerfs into the tenon and drive the wedges into these kerfs.
My understanding is that driving the wedgies into the kerfs produces
better results because the tenon actually "bends" outward so that the
wedged end is larger than the "inside" end ... locking the tenon in
place much like a dovetail joint. BUT ... you have to do this without
splitting the tenon when you drive the wedge in.
Questions about all this (keeping in mind that my tenons will be 1/2
inch wide by 2 inch long by 2 inch deep):
1. How far from each side of the tenon woud you make the kerf? 1/8
inch or so?
2. How LONG would you make the kerf? 2/3 the length of the tenon, or
about 1+1/3 inch in my case?
3. What do you think about this guideline of "1/8 inch for every inch
of mortise depth" for the question of how much to enlarge the mortise
on the "far" side? It sounds fine in theory, if my kerf is 1+1/3
inch long I just don't see how I can push the end of it it 1/4 inch
sideways without splitting it?
If anyone has experience -- good OR bad! -- making these joints, I'd
sure appreciate hearing your story. I realize that different wood
will have different characteristics, but I might still find your
experience helpful even if the wood is different.
Thanks in advance.