With the mortising machine all ready to go I can start on
the leg's through mortises. The first one
is where the bottom rail will go.
Following that will be the ones for the top pair of rails. This is the view of the legs along with the
rails and all the plugs that go into the mortises. 
A cutoff from the leg is used as a test piece to center
the mortise on the leg and set a stop to limit the depth the mortise is
drilled. In this case that’s 1½” deep
which does not go all the way through the 2 1/8” leg. To go all the way through I will come back in
from the other side finishing it up. It
is possible to go all the way through in one pass but I didn’t here for a
couple of reasons. First, I am a little
leery of cutting a mortise that deep as I am concerned that going so deep could
cause a problem in getting the chips ejected cleanly. Second and more important is a concern that
when the chisel exits it could blow out that face. After the depth stop is set the leg can be
clamped in the carriage as shown below.
I like to center the clamp on the mortise to apply even pressure to hold
the part in place. Once clamped in the
carriage the black rod on the right is set so the next leg can be put in
exactly the same place. Next the
carriage is moved so the chisel is aligned to the left side of the mortise and
a stop is set so I can come back to the same point on the next leg. Now I can make the first mortising cut.
Below on the left the first plunge cut has been made and
you can see the pile of chips that comes out of the hole. After that the carriage is moved to the left,
the chisel edge is aligned with the right edge of the mortise, a stop is set
for this location and the hole is drilled as shown in the right photo. The reason the end cuts are made first is so
they are square to the leg. If cuts were
made working across the mortise you can end up with one side of the chisel
being unsupported which could make the chisel drift to that side resulting in
an out of square mortise. 
With the first side done the leg can be flipped over and
using the same stops it’s cut deep enough to make the mortise go all the way
through. This cleans out the remaining
wood in the center and gives me a nice clean square mortise.
Now it’s time to do the last of the through mortises which are at the top of the leg. The leg on the left shows their location at the top and bottom of a groove where a panel will go. These will be cut from only one side and not both as the previous through mortises. That’s because the leg is tapered and the mortise only needs to go past where the taper gets cut. If you look at the right photo which is from the front you can cee the taper line on its the left. The two marked locations are for plugs that will hide some screws. Don’t worry if that does not make sense now as it will become clear later during assembly.
At the mortising machine I don’t have to change the front
to back location of the carriage as these mortises are also centered on the
leg. All that I have to do is clamp the
leg in place then set the black rod to locate the rest of the legs in the same
place. Another stop is set for the left
mortise and one is set for the right mortise.
The top photo shows the left mortise cut and the bottom one shows the
right one cut. In it you can see how
deep the chisel goes.
All went well until the last leg. As I was checking the location of the top
hole, I noticed that the chisel did not line up with my layout line. Double checking it with the other legs showed
the layout was right. At first, I
thought the stop had slipped but the chisel lined up just fine with one of the
other legs so that wasn’t it. After some
head scratching, I found the problem.
When cutting the legs to length I used a stop on the chop saw so all the
legs would be the same length but this one is short. The only think I can think of was a chip must
have gotten caught between the leg and the stop causing it to be cut a little
short. I could have loosened both the
stops and aligned the chisel with the layout lines but decided to shim the leg
the distance it was too short and proceed using the already set stops.
Next is to move to the intersecting mortises and there
are seven of those per leg. Some use the
½” drill/chisel and some use the 3/8” one. First, are the three ½” ones since that’s the
bit/chisel set that’s in the mortiser.
Below is the drawing showing the side rails and their intersecting
mortises.
These mortises do not go all the way through the leg but
do go far enough in to intersect with another mortise. If I just set up the needed stops and cut
away when the drill/chisel broke through into the already cut mortise the back
would probably get blown out. To prevent
that a shim that fits snugly in the previously cut mortise is installed to back
up the cut. Below you can see the shim
ready to go in and installed. From here
the stops are set and the mortise cut on two of the legs.
Because the legs are mirror images of each other after
the first two had been cut the stop that locates the leg in the carriage has to
be shifted from the left side to the right.
So as to not have to reset the left/right stops I moved the carriage all
the way to the left and lined up the right side of the chisel with the right
edge of the mortise then clamped the leg in place. Resetting the black rod stop on the right
finished the setup and the mortises were cut.
Next Up – Leg Mortises Part 2 & Rail Templates
No comments:
Post a Comment