cnc turned parts--First we will machine the overall diameter to size.

 
To do this, we need to skim the diameter and check the size. Take a fine cut along the bar, using the fine feed if you have one. Measure both ends of the bar. If you have set the lathe up correctly , the bar should be parallel. If it is not, adjust the tailstock before continuing. Assuming the bar is parallel, take an- other cut or two so that you are about 0.1mm larger than the finished diameter. Now move the tool in until almost at finished size and take a light cut about 10mm long along the bar. Repeat this cut to ensure the tool is not pushing off. Measure this diameter; you will probably have to wind the tailstock barrel back to get the mi- crometer onto the end of the bar. Only move the barrel back, do not slide the entire tailstock back. Measure the bar to find out how much to remove from the diameter. Take another short cut and check for size. When the bar is cutting to size, machine
all the way along. You will probably have to take two or three cuts at the same set- ting until the bar is machined to finished size.
 
Now we will turn the steps on the ends. To ensure that the steps are the correct length, we will use the bed stop. Set the bed stop, then wind the top slide so that the tool is just touching the end of the bar. For this exercise we will make the steps
12mm long. Wind the top slide along until the tool is just touching the end of the turned bar. Wind the top slide along 11.9mm. We can now rough out the step at each end. Turn the end down to about 0.2mm above the finished diameter. You can use the fine feed but make sure you knock the feed off before the carriage reaches the stop and finish up to the end by hand. Repeat for the other end. Wind the top slide along the remaining 0.1mm to 12mm and finish each end in the same way as you finished the main diameter. Don’t forget to clean up the face of the shoulder you have just turned. Congratulations, you have just turned an accurate shaft. Don’t worry if the shaft is a tiny bit undersize, you can probably make the mating holes to fit.