I had a job recently where I needed to machine some features and a thread on the end of some 3 ft sections of square bar. I made a headstock spider some time ago, but it was mostly for hex bar and occasional round bars, so it only had three screws. By drilling and threading three more M8 holes and making an extra brass-tipped lockscrew using my lantern chuck, I can now use hex, round, square and rectangular stock that's longer than the headstock tube but keep it centralised. Obviously I never let more than about 30x the stock diameter to stick out without using support rollers to avoid any risk of whipping. Where I'm making a load of custom nuts or bolts from hex bar, or washers/spacers from round stock, or indeed, odd things from square or rectangular bars, having the facility for three or four point support is useful. In general for washers, I use locknuts and set the screws so they are only just supporting the material so I don't have to release and retighten them every time.
Neil
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