Based on the chuck removal lock primarily for the ML7 Addison Gray and myself have developed a simple indexing devices for the ML7 and S7. These use the principle of a sine bar and maths small angle approximation to make it easy to rotate and set the spindle to any angle. Intended as a marking out and drilling aid, not for milling, requires no drilling or holes to affix and no calculations, since one turn = one degree.
Peter