The pantograph mill was, in many respects, the forerunner of CNC machines that are universally used in industry today. I use it for cutting out flat parts from sheet. A large-scale pattern of the component required is made from some easily-worked material such as styrene sheet. This is mounted on the copy table at the top of the photo, and the pattern is traced by hand using the stylus that can be seen set vertically in the end of the top arm. This is connected through the pantograph mechanism to the cutting head. This holds the cutter that cuts out the part in sheet metal that is mounted on the working table in the centre of the photo. The pattern is made to a large scale so that any errors are reduced in the pantograph and very accurate parts can be cut out, and multiple parts can be cut using the same master.
The whole process is described in more detail by Tony Reynalds in Model Railway Journals nos. 53, 74, and 116. Pantograph mills are no longer made but are often available second hand from machine tool dealers. Most of them were made originally by Taylor Hobson, but mine is by George Alexander. It was built to take tool bits with a particular (and unusual) taper. I adapted it to take conventional FC3 ("throwaway") milling cutters by making a toolholder of external dimensions identical to the original, but bored to the cutter shank dimension. The cutters themselves are held in place by means of a grub screw. By turning the shank of small Eclipse drill chuck to the same dimension, I can also fit small drills and use it as a high-speed drilling machine.
The photo below shows the original toolholder with an engraving tool in place, my copy, and the nut that secures either of them to the drive spindle.