I had a problem with a missing knob on the feed box for my lathe. The previous owner used a drift punch in the arm to lock the selection in.
This just don't cut it on a machine designed to make parts.
Looking thru my junk stuff pile I found a 5lb dumb bell with a knurled handle. The weights unscrew from the handle and a file test told me that it was easily machinable..
Hack sawed off the threads on one end and chucked up the handle. Drilled to size and depth for the arm and cleaned up the ends. Next problem was what to use for the engaging pin. A hinge pin seemed to be the perfect fit.
The end was cut off the right length to retain the flange in the arm when the pin was completely engaged. the cutoff end was then welded to the back of the flange. Next was the spring. A salvaged spring from a destroyed china bb gun was the right size. A 1/4" pipe nipple was cut off and threaded and screw driver slot put in to install the assembly in the arm. A side hole was drilled and tapped in knob and a set screw installed on the shaft.
Cheap and dirty works for me. While doing this knob I decided to make a new knob for the elevation knob on the tool post grinder that was broken. I turned, drilled the 3/8 bore and removed from the lathe. Drill press and x block for the retainer pin hole and installed.
I think I'll get 2 or 3 more knobs from this handle. I wish people would throw more of them away.