Workholding Insights: 5-Axis Machining

While cruising LinkedIn last week, I came across a post with a photo that showed a vocational classroom full of conventional knee mills and lathes. In the post the author was criticizing the use of conventional machines to train modern students. The author believes that students should learn machining on ‘modern’ machines like 5 axis machining centers while using CAD/CAM software. His belief is that students will not be able to function in modern manufacturing by learning ‘outdated’ methods and therefore these old machines and methods do not have a place in the curriculum.

Of course, students need to be exposed to CNC programming, 5-axis machining, and CAD/CAM software as part of the machine shop (tool making) curriculums, I don’t think anyone would argue. However, every student should start out on the conventional machines and demonstrate competence using them before they transition to CNC machining and CAD/ CAM programming.Educational Benefits of Conventional Machines

Setting up and using conventional machine tools are critical to success when a student transitions to more complex processes like CNC machining. Workholding, cutting speeds and the creation of the correct part geometry are best learned while standing in front of conventional machine tools and cranking on handles.

A competent and willing student can learn to write usable CNC code in three days or less. I have witnessed it. Teaching a person how to secure an odd-shaped part to the mill table or in a lathe chuck takes much longer. Workholding in a real machine shop is not always as simple as putting a rectilinear block into a vise or a cylinder into a lathe chuck. Students need to be exposed to parts that require creative approaches like machining a special set of jaws to hold an odd-shaped part or using a four-jaw chuck to create eccentric shapes.

Proper use of cutting tools is best learned through the feedback of a machine tool handle. Cutting tools impact four of the five senses. And when something is wrong, one or more of the four senses will provide an early warning signal. CNC machines insulate the machinist from sensory feedback. If a student is not allowed to feel how a dull endmill behaves or hear the sound of a squealing drill that is turning too fast, they are going to struggle to properly use and maintain tools in a CNC machine.