This probably applies to many lathes. I've just bought a very old circa early 1960s Boxford 4.5" AUD. The circumstances and price of sale didn't allow me to examine the machine in detail, and I now find that the fitted 3 jaw chuck is well and truly stuck to the mandrel nose. Have tried the lathe in locked backgear with a bar through the chuck jaws, but the torque applied (without success) makes me fear for the backgear teeth. Are there any other tips that are tried and tested, e.g.. heat, other ways of locking the mandrel etc. Does anyone have any idea of a safe torque to apply before damage to the mandrel itself. I believe if everything fails I could turn the chuck backplate away from the mandrel. has anyone done this, and has any tips to minimise risk to the mandrel threads and register.