Guide to CNC Lathe Machining and Turning Centers

March 27, 2019

The lathe is one of the oldest manufacturing technologies on Earth; in fact, its earliest version dates back to the Egyptians around 1300 BC. The technology has exponentially increased, become more and more advanced every decade, and today, lathes are used to create everything from artisan wooden bowls to large parts for heavy machinery.

Turning Center Basics

To get started, here are some basic definitions.

Lathe: Lathes are machines that shape material by rotating a drive, which turns the piece being worked on against cutting tools that can be switched out to obtain the appropriate cut.

Turning: Turning is the act of cutting a part on a lathe.

Tool: The tooling is the cutting mechanism affixed to the machine to build parts.

Turning Center: A turning center is a lathe with computer numerical control (CNC).

Headstock: The headstock holds the workpiece, provides power to various parts of the machine, and rotates the spindle.

Carriage: The carriage supports the cutting tool, guiding and feeding it against the workpiece.

Lathes vs CNC Turning Centers

Although they might look alike, horizontal CNC turning centers are an evolutionary leap from the CNC lathe machines of the past. Lathes, by definition, are 2-axis machines.

Once lathes evolved to include 3-axis, 4-axis and 5-axis capabilities, they became known as turning centers.

While there is no formal distinction, a lathe is typically used to refer to simpler machines, like those that only perform turning operations with usually just X and Z axes. A turning center, on the other hand, will likely integrate milling, drilling, and sub spindle capabilities and include a Y-axis. Today, the terms can be used interchangeably.

To some extent, a CNC turning center is less complicated to operate than a lathe because it is completely controlled by a computer, which can move all axes simultaneously and with great precision.

Turning Center Operations

Traditional lathes spin material, while a cutting tool gently takes material away to create something circular. There are many operations that can be performed on a lathe, but even more can be performed on a turning center.

Extra axes permit cutting around corners. The tools of traditional 2-axis lathes only regulate the diameter of an item. They cannot turn corners or cut inside. Multi-axis turning centers can move the tool to cut around a corner. This feature removes material that is out of reach of the traditional 2-axis lathe.

Turning centers drill, bore, and ream with ease. These operations occur in the center of the piece’s axis as it spins. There are also live-tooling features that can perform these operations on pieces when they are stationary. The tools drill and finish holes wherever the specifications require them. This feature eliminates the need to perform extra steps at different stations.

Knurling creates a natural grip for tools. Some machined parts, particularly tools, require the user to have a good grip on them. A smooth machined surface makes them slippery. Knurling presses a pattern into the surface that makes them easy to handle. Socket wrenches and other metal tools typically have knurled handles.

Cutting a taper is simple with more than two axes. Think about this as sharpening a pencil. Performing this function requires an option that is not available with CNC lathe machining. A taper makes the most sense at the end of the piece, but the technique can be applied anywhere along a piece’s length.

Turning center threading reduces machining time. In traditional lathes, threading is a separate step; an operator needs to remove it and apply the thread at a different station. This step takes time and adds an unnecessary element of risk. Precision threading holds the piece locked in place and can be a big time-saver.

Facing provides a clean edge and trims the piece to the correct length. The piece often starts as rough-cut stock. As part of the machining process, the turning center can face the rough edge. It can also trim the piece to the required size.

Horizontal Machining Center Applications

Horizontal machining centers can be used in almost every industry because of their capabilities and efficiencies. Since tool changes are automatic, it eliminates costly setup and machining time. Rather than moving the part to another station, turning centers can switch tools. The computer program drives the tool-change and does not usually require intervention by the machine operator.

Choosing Between Horizontal and Vertical Turning Centers

There are a lot of options when it comes to which machine is best for your part. When it comes down to it, make sure that the company you are using for contract manufacturing work is fitted with a variety of CNC machines.

There isn’t a single machine that can do it all. Machine capabilities, part size, and tooling requirements all play a part in machine selection, which is typically something your outsourced manufacturing vendor will be paying close attention to.

When it comes to horizontal and vertical machining, the main difference is the orientation of the spindle. Vertical milling uses a fixed spindle and is an excellent choice for projects that require work mostly on a single side, such as sinking dies and large metal plates. Vertical milling is often less complex internally than horizontal mills. Horizontal milling doesn’t use a fixed spindle, but instead, uses cutting heads mounted to a horizontal arbor.

Gravity also comes into play. In horizontal machines, gravity causes the metal chips to fall to the bed below, which keeps the piece clean during cutting. The same part in a vertical turning center might have a difficulty clearing chips, which is particularly true if the top has a bowl-shaped indentation. Such an indentation can hold the chips throughout the turning process.

A horizontal machining center is the simplest center for everyone to understand. It looks and operates very much like a lathe, accommodating a wide variety of material types and sizes. Everything the operator touches is easily within reach. Many can be set up to handle automatic bar-stock feeders. Gravity helps keep the cutting areas clean but may also cause a problem if the stock is too thin and sags.

A regular vertical turning center uses gravity to its advantage. The weight of the item helps hold the piece in the headstock. Clearing chips might be a problem depending on the application.

Here at Precise Tool and Manufacturing Inc., we pride ourselves on keeping up with the cutting edge of technology. We have an extensive operation with over 100 CNC machines and over 200,000 square feet of floor space. We look forward to the opportunity to exceed your expectations.