Metal Turning 101

Metal turning and spinning date back thousands of years. The first pictorial evidence that archaeologists uncovered in the tomb of the fourth-century Egyptian pharaoh Petosiris. The picture features an illustration of two men operating an ancient lathe. 

Technicians can do metal turning by hand, but most shops have incorporated mechanized lathes into their operations. Today, we’re going to look at an introduction to metal turning. We’ll cover questions like: What is metal turning? What metals can be turned? What can be formed through the process of metal turning? And more.

At Elemet Manufacturing, Inc., our experienced machinists and drafting technicians carefully match our technology with your design needs from beginning to end. You can rely on our metal turning processes to meet the highest-quality and most efficient standards. Contact us today!

What Is Metal Turning?

Turning is the most basic machining process. It is also the most common lathe machining operation. 

During the metal turning process, a cutting tool subtracts metal pieces from a rotating workpiece’s outer diameter. The main objective of metal turning is to reduce the workpiece to the desired dimensions. 

Turning can be on the external surface of the part or internally, also called boring. The material used in this production is generally a workpiece generated by other processes, such as casting, forging, extrusion, or drawing.

Metal turning is a form of machining. It is a material removal process used to create rotational parts by cutting unwanted material. 

The metal turning process requires a turning machine or lathe, a workpiece, a fixture, and a cutting tool. The workpiece is a piece of pre-shaped metal secured to the fixture. The fixture is attached to the turning machine and rotated at high speeds. 

The cutter is typically a single-point cutting tool connected to the device. However, some operations use multi-point tools. The chosen cutting tool feeds into the rotating workpiece and cuts away material in small chips to create the desired shape.

Turning produces rotational, typically axis-symmetric parts with many features, such as holes, grooves, threads, tapers, various diameter steps, and even contoured surfaces. Parts that are fabricated entirely through turning often include limited-run components, perhaps for prototypes. 

Metal turning is also commonly used as a secondary process to add or refine features on manufactured parts using a different approach. Due to the surface finishes and high tolerances that metal turning offers, it is ideal for adding precision rotational features to an element whose basic shape has already formed.

Now, let’s take an in-depth look at different types of metal turning and some complementary processes:

Boring

Boring is the metalworking process of enlarging a hole already drilled (or cast) using a single-point cutting tool (or a boring head containing several such tools). Boring is commonly used to achieve greater accuracy of a hole’s diameter and can be used to cut a tapered hole. Boring is the internal-diameter counterpart to turning, which cuts external diameters. 

Chamfer Turning

Similar to step turning, chamfer turning creates an angled transition of a square edge between surfaces with different turned diameters.

Contour Turning

In a contour turning operation, the cutting tool axially follows the path using predefined geometry. Multiple passes of a contouring tool are necessary to create the desired shapes in the finished product. 

Drilling

Drilling is the metalworking process of removing material from the inside of a workpiece. This process uses standard drill bits held stationary in the tool turret of the lathe. Separately available drilling machines can do the procedure.

Facing

Facing in the context of metal turning work involves moving the chosen cutting tool at right angles to the workpiece’s rotation axis. Facing is performed by the operation of the cross-slide. The first operation is often performed in the workpiece’s production and frequently the last – hence the phrase “ending up.”

Grooving

In metalworking, grooving is similar to parting, but grooves are cut to a specific depth instead of severing the part entirely from the stock. Machinists can perform grooving on internal and external surfaces and the part’s face (also known as face grooving or trepanning).

Hard Turning

Hard turning consists of metal turning for materials with a Rockwell C hardness more significant than 45. It is typically performed after the workpiece has been heat-treated. The hard turning process tends to replace more traditional grinding operations. 

Hard turning is appropriate for parts requiring a roundness accuracy of 0.5-12 micrometers or surface roughness of Rz 0.8–7.0 micrometers. Hard turning applications include gears, injection pump components, and hydraulic components, among other applications. 

Knurling

Knurling is cutting a serrated pattern onto the surface of a part to use as a handgrip using a specific purpose knurling tool.

Parting

The parting process, also called parting off or cutoff, creates deep grooves that remove a completed or partially completed component from its parent stock.

Polygonal Turning

Polygonal turning is a turning process in which non-circular forms are machined without interrupting the raw material’s rotation. 

Reaming

Reaming is a sizing operation that removes a small amount of metal from a hole already drilled. Reaming is used for making internal holes of extremely accurate diameters. For example, a 6mm hole is made by drilling with a 5.98 mm drill bit and then reamed to precise dimensions. 

Spherical Turning

Spherical turning produces a ball shape on the workpiece.

Step Turning

The process of step turning creates two surfaces with an abrupt change in diameters between them. The finished product resembles a step.

Tapered Turning

Tapered turning produces a conical surface by gradual reduction or increase in diameter from a cylindrical workpiece. This tapering operation has a wide range of use in the construction of machines. 

Almost all machine spindles have taper holes that receive taper shank of various tools and work holding devices. Tapered turning produces a ramp transition between the two surfaces of the workpiece with different diameters. The result is due to the angled motion between the workpiece and a cutting tool.

Threading

Both standard and non-standard screw threads can be turned on a lathe using an appropriate cutting tool. Either externally or within a bore, generally referred to as single-point threading.

What Metals Can Machinists Turn?

Now that we’ve covered “what is metal turning,” let’s turn to what Machinists can turn materials, and they utilize several different metals in the metal turning process:

• Ferrous metals, such as iron, steel, or cast iron
• Aluminum
• Brass and other copper alloys
• Hi-temp nickel alloys
• Titanium
• Other non-ferrous metals

Why Work With A Metal Turning Shop?

There’s no easy way to describe the benefits of high-quality, precision machining and its importance in today’s manufacturing economy. Hopefully, today, we’ve answered the primary question, “what is metal turning”? 

At Elemet Manufacturing, Inc., our experienced machinists and drafting technicians carefully match our technology with your design needs from beginning to end. You can rely on our metal turning processes to meet the highest-quality and most efficient standards. Contact us today!