Back when there were only a few TIG torch manufacturers (and none of them imported from Asia) the cost was very near prohibitive for a home shop. Lack of common sense supplemented with a truckload of determination make this a small mountain to climb.
I wound resin-saturated fiberglass tape around a waxed wood dowel form to get the basic shapes. Finished the shapes with a disk sander.
Belt Sander ?? What's that?
I made the metal parts from brass plumbing fittings chosen for their size and shape. With no handy source of raw materials, it was cheaper and easier to use a 1/2 inch brass pipe plug than to procure a chunk of round brass stock that size. IIRC: The collet was made from a small brass plumb bob. Since I was using borrowed lathe time, I minimized machine work in any way I could. A habit that I have yet to break after 30 years with my own lathe.
The cups were commercial items chosen for price and availability. I turned and threaded the brass collet tungsten holder OD to more of a "screw-it-on-so-it-stays" situation than "to fit" the cups.
I have never claimed it to be beautiful but it did work. I still have it. It still works.
And, I still can't get over what some people (me) will do when they have more time than money.