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Machine Design

Inventor's Corner: Device turns milling machine into a CNC LATHE

The Sturges Turning Head by Dan Sturges of Sturges DesignWorks, Portland, Oreg., lets users produce prototypes, one-offs, custom machines, and devices that require CNC lathe parts. Basically, the Turning Head is a lathe module for milling machines. Users get most of a CNC lathe’s capabilities at a small fraction of the price. The device incorporates a quality, yet compact, lathe headstock and a toolholder. It lets users easily make high-precision lathe parts on their milling machine.

Many businesses don’t have a CNC lathe because of the expense, infrequent need, or space restrictions. However, many companies do own a CNC milling machine. A Sturges Turning Head lets shops use their milling machines to produce most CNC lathe parts.

Before the invention, shops were either buying a full-featured CNC lathe (expensive!), farming out the CNC lathe work (with all of the associated costs and headaches), or, worse, compromising their designs to accommodate their manual lathe’s limited capabilities and repeatability.

Here is how the Sturges Turning Head works: The headstock is direct or vice-mounted on the milling table. The toolholder mounts in the spindle just like any other tool such as an end mill or drill chuck. The toolholder uses indexable carbide inserts. The headstock rotates the work and the milling spindle presents the cutter to the work, just like a lathe. However, the milling spindle does not rotate, but instead is either locked, clamped, or left in a neutral position. The tip of the carbide cutter is precisely in line with the milling spindle axis so the cutter can be presented for left or right-hand cutting without affecting the cutting edge location. Rotating the milling spindle doesn’t affect the cutting edge’s location or the CNC program. The headstock spindle also manually locks and indexes the work. This feature lets machinists use end mills, drills, and the like to perform milling operations on their lathe part, in the same set up.

Sturges got the idea because his company designs and builds custom-engineered machines and devices. A particular machine required several dozen pulleys for 3–/8˜-in.-diameter urethane belting. These parts would be impractical to make on an engine lathe and too costly to farm out. Sturges decided to use the CNC capability of the shop’s milling machine to make the parts.

Tools Sturges used in building his invention include SolidWorks 2012 CAD to design the entire system. The pulley guard was prototyped using 3D printing. The prototype model was then used as a master to cast the pulley guard from hard polyurethane. The Turning Bar toolholders were made using the Turning Head System itself.

The Turning Head spindle and Turning Bar toolholder are patent pending. Contact Dan Sturges at [email protected], (503) 233-3041.


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