With this series of chairs, my control of leg and spindle angles is much improved. I've changed how the holes are bored in the arms and the seats. I made a new jig, shaped like the arm, into which the arm nests and is clamped down. It is made of particle board, and is half round, the same diameter of the seat back. On the face are parallel lines; these I align with the pencil marks the on the arms, where the 5/8" holes will be bored. With an odd number of spindles I always start by marking the location of the center hole. Then the others are marked out with a compass/pencil at 2 1/4" on center. I have a number of elm blocks, some 2" x 6" x 8", each end of which is cut to a different angle. I rest the block on the pencil line on the particle board, and keep the auger bit to the correct angle by eye. We must get some photos. The holes bored next are those in the seat. Their location is marked on the seat in the same manner as the arms, however I no longer drill them straightaway. I've made a frame to the height of the short spindles, about 9". I clamp this frame to the seat, and them clamp the arm to the frame. I am thus able to hold the arm in its final position, i.e., it's neither to the left or the right. Then I slide in the long spindles and see just how they really do line up with the marks I've already made. Rather than having to cheat a spindle in place after boring a hole, I can move the marks around a bit, this minimizing having to force any spindle into place. And I can more readily maintain the symmetry of the spindles.
The holes for the short spindles are bored next. The angle is usually 7 degrees, but is somewhat a function of the width of the arm. Coming off the glue and steam bending clamps, the arms can spring not at all, or more than not at all. At 8 1/2" above the seat, and at varying widths, the angles of the spindles change. (The math is easy to figure out; and I keep it written on the sheet rock in the shop.) Having said all that, there is a lot of wiggle room with the short spindles, and it's better to move them to fit the arm, rather than the other way round. Again, I have a piece of ply with pencil lines, and a block to guide angles and uprightness of the spindle holes. However, having bored these, I put the frame back on the seat, with the short and long spindles in place, and see just where the former end up in comparison with the marks I've made, where I 'think' they should go. Again, anything too far out is easily spotted, and I can adjust things. The 1/2" holes in the arms for the short spindles are the only holes made not using my Millers Falls brace. (The Makita cordless is a very nice drill.)
Another favorite seat. Note the grain lines on the seat, left and right where the short spindles go in; not by accident. Also, but only barely visible are the matching grain lines on the front of the seat, left and right.
Spot on legs!