Mastering basic turning skills

Turning and other lathe operations are the most common machining applications. A master tool and die maker once told me a lathe is the only piece of shop equipment that can remanufacture itself. Whether or not the statement is factual is not important. Having the lathe described in that manner indicates how important and universal turning is to manufacturing.

The lathe is one of the first machines tool and die students learn to operate. This is because the procedures and techniques that are learned on the lathe have application on other machine tools.

Industry has, for many years, been adopting technology that limits machinists’ interaction with the machine itself. Things like CNCs and CAD/CAM software enhanced the manufacturing environment and will continue to improve manufacturing processes but are diminishing fundamental skills.

There is a set of old-school lathe skills that every machinist, toolmaker and engineer can learn to directly impact their effectiveness in today’s machine shop. For example, machinists should learn to turn an eccentric shape on the lathe. Eccentric shapes can be made in several ways but are typically made by offsetting the workpiece using a 4-jaw chuck. Learning to master the 4-jaw chuck and understanding how to align parts has direct application on any machine tool with rotating elements.

The lathe is one of the first machines tool and die students learn to operate. Image courtesy Sandvik Coromant.

A previous employer of mine was having scrap issues with an aluminum casting that had hydraulic ports drilled using a rotary table attached to a vertical machining center. The two ports were drilled at 90° to each other, and we kept having problems with the ports being too close to the edge of the casting, leaving a wall that was too thin. After investigating, I found maintenance had replaced the collet chuck mounted on the rotary table; the collet was running out and causing the part centerline to shift by a few millimeters. Shifting a part centerline using a 4-jaw chuck produces the same situation, and I may not have found the solution had I not spent time aligning parts in a 4-jaw chuck. Similar to a 4-jaw chuck on a lathe, the collet chuck on a machining center could be adjusted using four setscrews. This adjustment allows the user to drive the axis of the collet chuck so that it is aligned to the center of the rotary table.