The carriage bolt screws into one end of the turnbuckle. The other end attaches to a hinge bolted to the arm drive plate. The belcrank adjusts the total throw and the turnbuckle adjust centering. My design did require the use of a lathe, but careful selection of shafts, bearings and pulleys might eliminate the need. I also used a welding torch for brazing.
Braising is rather a no-brainer compared to welding.
You do it like soldering, but at a much higher temperature. Most wood joints were made with carpenter's glue and screws. When viewed from the table end, looking across toward the arm assembly the table rotates counter clockwise, and the arm is set to swing to the left. Both motors are grounded. As the works of this machine are exposed considerable care must be exercised to prevent injury.