Take Your Metal for a Spin

In metalworking, a lathe is a machine that rotates a piece of metal at high speeds so that a tool applied to the surface of the spinning workpiece can cut or perform some other action to the metal as it makes contact. When a machinist needs to create a cylindrical part that is symmetrical, such as a screw or a gun barrel, he uses a lathe to produce it. Lathes are very common in woodworking, where they originated in ancient times, but our focus here is on metal turning lathes. 

The most common function of a lathe is “turning,” which involves using a tool to remove metal from the outside of the workpiece as it spins. It can be performed uniformly along the length of the workpiece, shaping the outside to the same diameter, or can be applied as different configurations, including step turning (different diameters at different points along the workpiece, with a sharp, steplike transition between them), contour turning (different diameters with a curving transition between them), and taper turning (creating a conelike shape in the workpiece).

Different tools can be installed on a lathe to perform additional functions with the metal, including: 

  • Boring
  • Cutting
  • Deformation
  • Drilling 
  • Facing
  • Forming
  • Grinding
  • Grooving
  • Knurling 
  • Parting
  • Polishing
  • Reaming
  • Sanding
  • Shaping
  • Tapping
  • Threading

Parts of a Lathe

While lathes are constructed in different ways, the common features found on most of them include:

  • Bed. The base of the lathe to which all other parts are attached is called the bed. Slideways along the bed keep the positions of the carriage, the tailstock, and the support devices, known as rests, in alignment with the spindle. How large of a workpiece a lathe can turn depends on how high the spindle is from the bed.
  • Carriage. Tooling is held and moved into position against the workpiece by the carriage.
  • Headstock. The headstock is the powered end of the machine, almost always found at the left side when facing it.  It includes the main spindle—which is often hollow to allow long workpieces to be machined—and the controls and mechanisms for directing the lathe’s spinning operations, such as speed. The motor will be found mounted to the lathe near the headstock. Various devices for holding and positioning workpieces can be attached at this end of the lathe, including chucks, faceplates, centers, and tapers.
  • Tailstock. The tailstock is found at the right side of the lathe, opposite the headstock. It can change position along the slideways in the bed and is used for holding a drill bit or other tooling.

The Legacy of Lathes

The history of the lathe goes back to before recorded history. The original “lathe” is the pottery wheel, a device for spinning material that could be shaped by hand, symmetrically around the center axis. Well over 3,000 years ago, Egyptian craftsmen discovered that one worker could use a strap or rope to spin a piece of wood while a second worker shaped it with a tool. The ancient Chinese learned that they could use the principle of the lathe to sharpen weapons and tools. Romans and Vikings alike utilized types of lathes in their woodworking projects.

Power sources to get the workpiece to spin advanced over the millennia, from hand and foot powered devices to water wheels and steam engines during the Industrial Revolution. These later machines could produce enough torque to rotate heavier parts, allowing metal to be machined along with wood.

Leonardo da Vinci (1452–1519) conceptualized on paper a continual rotation lathe that could be operated by one person. In 1718, Russian engineer Andrey Nartov designed and built a lathe with a mechanical carriage to support cutting tools. English machine tool innovator Henry Maudslay (1771–1831) invented the first metal cutting lathe, among other devices. 

Metal lathes continued to advance in design through the 19th and 20th centuries, with the advent of the electric motor making lathes more versatile and powerful. In the middle of the 20th century, lathes with servomechanisms began to appear, first operated by numerical controls (NC) and later by computer numerical controls (CNC). Despite all the advancements in the field, however, simple manually controlled lathes remain popular with hobbyists and many machines today.

Types of Metalworking Lathes

Metal lathes come in a variety of styles. Some of the more common ones include:

  • CNC Lathe. A computerized lathe that utilizes a programmable computer numeric control (CNC) to automatically run the lathe’s operation
  • Combination Lathe. Designed for hobbyists, it combines milling and/or drilling with standard lathe operations. Lathes that have all three are usually called 3-in-1 machines.
  • Engine Lathe. The traditional type of lathe of the last two centuries, the engine lathe gets its name from the powered carriage it features to hold and move the tooling, in contrast with earlier lathes with manually fed or handheld tools.
  • Multi-spindle Lathe. A high-volume production machine with more than one spindle and automated controls.
  • Oil Country Lathe. A long lathe with a large spindle hole that is used for turning extremely long workpieces, such as segments of drill string (the long drilling pipe used in oil drilling rigs).
  • Swiss-style Lathe. A very precise lathe used for extreme accuracy.
  • Toolroom Lathe. A high-quality lathe intended for heavy-duty work. It is usually larger, more accurate, and smoother running than a standard engine lathe, and often comes with more optional tools and features included with it.
  • Turret Lathe. A lathe equipped with a turret that exchanges different cutting tools quickly throughout a single operation to perform different functions on the same part. 
  • Vertical Lathe. A lathe used for stability with larger workpieces by holding them upright on a turntable in a vertical configuration.

The Mother of Machine Tools

The lathe has been called the “mother of machine tools,” as it was the earliest machine tool invented and the inspiration for other workpiece shaping machines that began to be innovated in the Industrial Revolution and later. Along with a milling machine, the lathe is the centerpiece of a machinist’s shop and will likely be around a long as there are round metal parts to be made.