The main frame is made from 0.100" x 0.7" x 7.0" aluminum bent to form a 3" overall length.
The threaded rod is just some 5/16" fine all thread that I had. The entire unit is 4" total length.
The square steel piece that grabs the pinion is indeed steel tubing.
My shop is in the basement and has all of my stuff that I would consider my shop machining, and clockwork.
Size is about 10' by 12 '
Work area is in two groups, One is tall where I can stand and work and is about elbow height when I am standing. The other bench is traditional heavy...
If you have a dollar store near by, you can get a retractable usb cable, key chain, pet leash or anything else that is small and retractable and take the return spring out of it. Even a piece of feeler gauge.