What is a Turning?(milling titanium Marvin)
- source:WEINBERG CNC Machining
How Does Turning Work?
Turning employs a single point cutting tool, usually made of high speed steel, carbide, ceramic or diamond. The cutting tool is held rigidly in a tool holder that is mounted to the machine's tool post. The axis of the workpiece is aligned with the axis of rotation of the spindle. The spindle rotates the work at a constant speed while the cutting tool is slowly fed into the work axially, cutting away material to create the desired diameter.
The depth of cut is set by adjusting the cross slide, which moves the tool perpendicularly to the spindle axis. The feed rate determines how quickly the tool moves towards the spindle during the operation. After each pass of the tool, the tool is retracted, the cross slide is adjusted to give the next depth of cut, and the process repeated until the final diameter is achieved.
Types of Turning Operations
There are several basic turning operations, depending on what needs to be accomplished:
- Facing - Smoothing and squaring the face of a workpiece. This is usually done first to create a smooth reference surface.
- Straight turning - Reducing the diameter of a cylindrical workpiece to a specific dimension. This can be done from external to internal or vice versa.
- Taper turning - Creating a tapered diameter by turning at an angle to the spindle axis. Done by offsetting the tailstock or tool post.
- Grooving - Cutting narrow, grooved cuts into the workpiece. Used to cut grooves for O-rings, seals, parting cuts, threading, etc.
- Undercutting - Forming a recess in the workpiece by overhanging the cutting tool past the outer diameter. Useful for ornate shapes.
- Parting - Separating a workpiece into two parts by cutting entirely through it. Uses a specially shaped parting tool.
- Boring - Enlarging the internal diameter to precise dimensions. Requires boring bars to reach internal surfaces.
- Drilling/counterboring/reaming - Creating holes by feeding rotating cutting tools axially. Reaming is used to enlarge and finish holes to tight tolerances.
- Knurling - Creating a textured pattern of small ridges pressed into the workpiece using a knurling tool. Provides better grip for handles, fasteners, etc.
- Threading - Cutting helical threads into workpieces using thread cutting tools. Many pitch sizes and thread forms possible.
Turning Machines and Equipment
The most basic turning machine is the engine lathe, which firmly holds the workpiece between two points called centers while it rotates at speeds up to 2500 RPM. Tooling is mounted on the cross slide and tailstock for feeding and support. Engine lathes can handle work up to several feet in length. Smaller, more basic machines are called bench lathes.
For high volume production, computer numerically controlled (CNC) lathes automate the process. CNC machines use programmed instructions to control feeds, speeds and tool paths. This enables fast, consistent results with minimal operator input.
Chucks are used to hold non-cylindrical workpieces. Popular types include 3-jaw, 4-jaw and collet chucks. Faceplates hold work against a plate using clamps or adhesive. Centers can hold square or hex stock by applying pressure against the workpiece axis.
Cutting tools come in many styles for specific needs ranging from rough cutting to precision finishing. Carbide inserts with special geometries and coatings provide long life under high speeds and temperatures. Coolants and lubricants help regulate tool temperature while flushing away chips.
Applications of Turning
Nearly all manufactured parts require some form of turning operation during their production. Turning can create any rotational symmetric shape from common shapes like cylinders, cones and spheres to complex contours or patterns. Typical applications include:
- Engine components - pistons, crankshafts, camshafts, connectors, turbocharger impellers
- Drive components - shafts, axles, spindles, rollers, bushings, pulleys
- Cutting tools - drills, endmills, taps, reamers, boring bars
- Plumbing parts - pipes, fittings, valves, nozzles
- Aerospace parts - hydraulic components, spacers, sleeves, fasteners
- Ordnance - shells, barrels, warheads, grenades
- Automotive parts - brake rotors, drums, wheel hubs, drive train parts
- Fasteners - screws, bolts, nuts, pins
- Precision instruments - discs, cams, fittings, gauges, nozzles
From tiny delicate medical implants to massive tunnel boring machine cutters, turned components cover a vast range of sizes, shapes and materials. Continued advancements in cutting tools, automation and computing power ensure turning remains a versatile and evolving manufacturing process. CNC Milling