I had this machine a long time ago and had a lot of trouble getting the auto tool post to lock in place.First the shaft should be locked don't mater how or were as long as it is . 2 the rotation is just a number of steps forward and locking is reverse until the steper stalls simple as that , just experiment to find how many degrees to go .3 I had to fit a stronger steper to get it to hold fast and also increased the power . All this eventually worked although the toolpost macro was as usfull as a chocolate teapot ,just set it up as a axis and set it for degrees.The whole thing is very primitive . I now have a M300 that works a great deal better