See how easy it is to change or replace the shaft in an SQM5 actuator. The shaft shown is the dual ended 3/8" square shaft, by far the most common. If you're working with a single ended shaft, the process is similar, save for the C-clip & washer on the non-gear end..
Written instructions are on page 7 of the technical literature: https://scccombustion.com/wp-content/...