Take the cover off at the rear of the spindle . You will see 2 proximity switches . 1 for External Clamp, 1 for Internal clamp . ) External clamp the cylinder moves towards you , Internal clamp the cylinder pushes towards the chuck . Clamp the part internally then slide the internal one so the orange light goes out . It is a safety function for the Chuck Stroke so that the chuck is not on the extent of its stroke when clamping .