What Is a Lathe (Turning Process)? What Can It Make? Basic Knowledge on Mechanism and Features

What Is a Lathe?

The lathe is the most commonly used machine tool in manufacturing sites. Here, we will cover the basic knowledge of lathes, including their mechanism and history, which are indispensable in the manufacturing industry.

Lathe (Turning Process) Fundamentals: Characteristics

In a lathe, the workpiece is attached to the spindle and rotated. A cutting tool is then applied to the workpiece to perform the cutting process. The basic principle of machining is that the cut shape and size of the workpiece will depend on the cutting tool used. Lathe machining includes various methods such as straight turning, thread cutting, and drilling, and is also called "round parts machining" as it can be used to make roundish products.

History of the Lathe

Machine tools can trace their origins back to the bow-lathes of ancient Egypt. A bow drill, the lathe's progenitor, is depicted in Egyptian murals from c. 1480 B.C. At that time, it was used as a machine tool for woodworking of wood structures.

In Japan, it was during the Meiji Era (1868-1912) that lathe technology began to develop. Sometime around 1875 (the 8th year of the Meiji era), a man named Kaheiji Ito made a pedal-driven lathe in his hometown in Yamagata. Incidentally, Ito is said to have learned machine manufacturing at Tanaka Engineering Works, Japan's first machine manufacturer and predecessor to Toshiba.

Later, as modernization and industrialization progressed, machine tool technology developed significantly. Since the 1970s, advanced machine tools such as NC lathes have emerged, and Japan has grown into a world leader in machine tools. In recent years, machine tools are becoming increasingly multi-functional and smaller as the market demands high-mix, low-volume production, and demand is increasing for compact machining centers, multi-tasking machines, and the like.

Difficult to Operate?

Despite being the most basic machine tool in the manufacturing industry, the lathe is sometimes said to be difficult to operate. Some reasons given for this are difficulty with drawings, the multitude of tool options, and tools breaking if the cutting conditions are wrong.

Lathes require precise positioning of the workpiece and tool and careful operation. They can be mounted with a wide variety of tools, and the right tools must be selected according to workpiece characteristics. Lathe operation requires a certain level of workmanship and proficiency. A mismatch between cutting conditions and tool settings can break the tool or result in a machine failure. In other words, it can also be considered profound work.

Differences From Other Machine Tools

In addition to lathes, other machine tools include the milling machine and machining center. This section will describe the characteristics of each and their differences from the lathe.

The Lathe vs. the Milling Machine

The milling machine is another iconic machine tool on par with the lathe. In a lathe, the workpiece is mounted on the spindle and rotated, whereas in a milling machine, the cutting tool is rotated for machining. If it makes it easier, imagine a lathe as like a potter's wheel and a milling machine as like carving a sculpture.

Due to these differences, the lathe is suited for machining of cylindrical and conical (tapered) shapes, while the milling machine is more suitable for linear cutting and multi-face machining.

The Lathe vs. the Machining Center

Machining center generally refers to a milling machine equipped with an NC unit and automatic tool changer (ATC).

The machining center allows for multiple machining methods, such as cutting and grinding, to be performed using a single machine. By programming the machining details, the machine will change tools between processes automatically, allowing for the entire process to be automated, from workpiece setup to machining completion.

Types of Lathes

Lathes are classified into several types according to their structure: manual and automatic, vertical and horizontal, and so on. Next, we will explain the types of lathes.

Universal Lathe

A lathe that is manually operated is called a universal lathe, or sometimes a normal lathe or standard lathe. Even today, with numerical control (NC) being the norm, universal lathes are widely used in manufacturing due to their high flexibility. Unlike with NC, these lathes do not require designing a program, so they are used for manufacturing custom-made parts and prototypes.

NC Lathe (Numerical Control Lathe)

An NC lathe is a lathe that can perform computer-controlled machining. NC stands for "numerical control," and with an NC lathe, operation can be automated according to the programmed instructions. With their ability to maintain uniform quality regardless of operator skill, NC lathes are suited to mass production and the manufacture of parts with complex shapes.

Bench Lathe

Exactly as the name suggests, a bench lathe is a small lathe that can be used on a table or bench. Given their ability to work in a limited space, bench lathes are used not only in the manufacturing industry but also in DIY and other settings. Many are manual operation, but there are also high-performance bench lathes with NC.

Vertical Lathe

A vertical lathe is a lathe in which the spindle is positioned perpendicular to the ground. With the headstock aligned with gravity, vertical lathes are characterized by stable machining, even for heavy workpieces and asymmetrical workpieces. On the other hand, their disadvantage is that chips accumulate more than with horizontal lathes. Vertical lathes are occasionally called turning centers, but JIS (Japanese Industrial Standards) defines a turning center as a machine tool equipped with an NC unit, automatic tool changer, and other features.

Front Lathe

The front lathe is a lathe dedicated to face milling. It has a large diameter faceplate for machining large workpieces. The spindle is horizontal and cuts from the front of the workpiece. There are front lathes that can handle workpieces sized from tens of centimeters to more than 1 meter, which are widely used in sectors such as aerospace and heavy industries.

Turret Lathe

A turret is a device that can be mounted with multiple tools. With a turret lathe, the tool can be changed simply by rotating the turret for seamless operation of a series of cutting processes. However, with the advent of NC lathes and multi-tasking machines, they are rarely used today.

Multi-Tasking Lathe

The multi-tasking lathe is a high-performance lathe, capable of not only turning process, but also milling and other machining operations. The 5-axis machining center, which has the functionality of a lathe and machining center with five axes of travel, is also a type of multi-tasking machine. With their high machining accuracy and productivity, multi-tasking lathes are used in manufacturing sites in various fields regardless of industry.

Mechanism and Part Names of a Lathe

Let's take a look at the basic parts of the lathe.

Headstock

The headstock refers to the faceplate onto which the workpiece is mounted, and the shaft or motor that rotates that faceplate. This is the heart of the lathe, and it greatly affects lathe performance.

Bed

The bed is the base of the lathe and serves to support the other key components. If the entire machine shifts due to vibration from rotation, it will decrease machining accuracy. In order to perform stable machining, the bed must be of high strength and rigidity.

Tailstock

The tailstock is a stand opposing the headstock. The tailstock holds the workpiece with a tool called the center.

Carriage

The carriage consists of the turret, apron, and other parts, and it moves from side to side on the bed. While carriage movement is controlled manually in some cases, in an NC lathe, computer-controlled automatic operation is most common.

Feeder

The feeder moves the turret mounted with cutting tools in the vertical and horizontal directions, and its feed rate can be adjusted to make the cut properly.

Chuck

A chuck is a claw-like device used to fix the workpiece to the spindle. With the chuck, the workpiece is firmly mounted to the spindle and can be machined in a stable state. There are 3-jaw chucks, 4-jaw chucks, and electromagnetic chucks.

What Can It Make? What Is Its Purpose? Lathe Machining Methods

Depending on how the lathe is used, it can perform various machining operations, such as outer diameter machining, thread machining, and groove machining. Next, we will introduce the various machining methods of lathes.

Outer Diameter Machining (Straight Turning)

Outer diameter machining is a machining method for shaving down the outside of a cylindrical workpiece. The workpiece attached to the spindle is rotated at high speed to scrape the outer surface with a cutting tool. This method of machining is used to manufacture cylindrical parts such as shafts and rollers.

Inner Diameter Machining

Inner diameter machining is the method of machining the inside of a cylindrical workpiece. As the cutting tool is inserted inside of the workpiece, a cylindrical hole or cavity is created in the workpiece. Inner diameter machining is used for applications such as finishing the inside of bearing housings and pipes, and tool length must be adjusted according to the hole depth.

Taper Machining

Taper machining is a method for machining a slope (taper) onto a conical workpiece. In the cross-sectional view of the workpiece, the angle of spread from the center axis is called the opening angle, with the workpiece machined to the prescribed angle by adjusting the turret angle and feed rate.

End-Face Machining

On a cylinder, the bottom and top parts are the end faces. In end-face machining, the workpiece is machined by pressing the cutting tool against the end faces. This method is suited to finishing the ends of cylindrical parts flat. In a broader sense, chamfering to round corners can also be considered a form of end-face machining.

Boring

Boring is the machining method of drilling holes in the workpiece center area. Boring is used to make large holes and for side cutting of holes. There is also a boring machine, which is a dedicated machine tool for boring.

Drilling (Hole Machining)

Drilling is a method of machining to drill a hole in a workpiece, primarily performed using a drill mounted on the tailstock. This method is used to machine pilot holes in parts for boring.

Thread Machining

Thread machining with a lathe is used to make helical cuts in the workpiece. The machining method for creating grooves on the side surface of the workpiece is called outer diameter thread machining, and for cutting on the inner surface, it is called inner diameter thread machining. Thread machining is used in the manufacture of screw shafts and nuts, and it is performed using a cutting tool called a threading tool.

Groove Machining

Groove machining is a method for carving grooves on the outer surface of a cylindrical workpiece. This method is used to create various types of grooves according to the purpose, such as oil grooves and decorative grooves.

Arc Machining

Arc machining involves machining workpiece corners into a rounded or curved shape. This method is used in the manufacture of curved parts such as rollers, bearings and cams.

Parting Machining

Parting machining is a method for cutting off a part of the workpiece using a lathe. A parting tool is used to cut the workpiece into ring shapes. This method is suitable for cutting bars and tubing to specified lengths.

Lathe Terminology That You Should Know

Here are some terms related to lathes that you may be afraid to ask.

Zero-Point Calibration

Zero-point calibration (zero-point alignment) is the process of accurately setting the position of the workpiece to be machined. The tip of the cutting tool is put in light contact with the workpiece, and the cutting depth is adjusted based on that reference point.

Lathe Marks

Lathe marks are visible marks left on the machined surface from lathe machining. Also called machining marks or other names. If the cut is rough, the cutting surface will have irregularities. When a high quality finish is required, settings such as the spindle speed and cutting speed must be set appropriately.

Gouging

Gouging is a phenomenon in which metal is gouged out of the workpiece with a cutting tool. Possible causes for gouging include reduced cutting performance due to tool wear or chipping, or improper chip evacuation.

Center Unmachined Area

In lathe machining, this refers to the unmachined area left in the center of the workpiece in end-face machining and inner diameter machining. This is caused by the tool not fully reaching the center of the workpiece.

Relief Grooves and Cuts

In lathe machining, a relief groove or relief cut refers to intentionally cutting corners and edges of the parts being machined. Grooving corners can reduce man-hours and increase work efficiency.

The Future of Lathes

With technological innovations, the lathe continues to improve in functionality and machining accuracy. Upgrading equipment is bound to lead to productivity improvement. We will close with some words on how to choose a lathe and recommended products.

Universal or NC Lathe?

Most universal lathes are operated manually, and product quality will depend on the operator's skill. On the other hand, universal lathes are more flexible and suited to machining of small lots and special shapes. Meanwhile, NC lathes can be programmed for precision control, making for highly consistent, repeatable work that is suitable for mass production. Each has its advantages and disadvantages, so it is important to choose the type of lathe that aligns with your company's projects and production needs.

How Much Can Be Automated?

Throughout the country, the Japanese labor shortage worsens due to declining birthrates and an aging workforce. With so many manufacturing companies struggling with labor shortages, each is getting creative to reduce manpower and automate labor. As one solution, an increasing number of companies are introducing NC lathes and turning centers.

For example, once introduced, a multi-tasking machine can automate everything from material machining to tool changes and finished product removal with a single machine. Introducing machine tools with high machining performance and energy saving performance can help to establish a highly profitable production system by reducing labor costs and electricity costs while increasing productivity.

Reducing Human Resources and Increasing Productivity and Speed

The Brother M series of multi-tasking machines can achieve manpower reduction together with productivity improvements. The multi-tasking machine can perform lathe machining and machining operations such as milling on a single machine tool, minimizing the chores of workpiece changeover and tool changes. Equipped with simultaneous 5-axis function, they also support complex multi-face machining. Feel free to contact us if your company is looking to automate machining operations or reduce manpower with multi-tasking machines.