Let’s go over what my dimensions are:
I used scraps I had around the shop,
Base 32×16 x 3/4 melamine
table 36×12 x 3/4 melamine
Arms 36×3/4×5/8 oak
arm support (rides on top of the arm) 30×5/8×1 1/2
tower 2 1/2×7/8×13 from the base
You can see the arm top and arm are glued together perpendicular to each other for strength.
The arms are attached about 4” in from end with the lower arm 3” off the base and the upper 8” off the base. This is the critical dimensions, a scroll saw blade is 5” so when the blade is attached to the middle of each arm, it is close to being square( actually rectangle). The trickiest part is to keep the arms parallel and get the maximum stroke.