Turning: Engine Lathe
Turning is another of the basic machining processes. Information in this section is organized according to the subcategory links in the menu bar to the left.
Turning produces solids of revolution which can be tightly toleranced because of the specialized nature of the operation. Turning is performed on a machine called a lathe in which the tool is stationary and the part is rotated. The figure below illustrates an engine lathe. Lathes are designed solely for turning operations, so that precise control of the cutting results in tight tolerances. The work piece is mounted on the chuck, which rotates relative to the stationary tool.
Turning
Turning refers to cutting as shown below.
The term "facing" is used to describe removal of material from the flat end of a cylindrical part, as shown below. Facing is often used to improve the finish of surfaces that have been parted.
Turning: Engine Lathe Detail
Engine Lathe Carriage
The figure below illustrates the carriage of an engine lathe. The carriage allows cross-feed and diagonal movements in addition to axial movement.
Turning: Chucks
The chuck is integral to a lathe's functioning because it fixtures the part to the spindle axis of the machine. Below is shown a three-jaw chuck with jaws that are all driven by the same chuck key. This arrangement provides convenience in that parts can be mounted and dismounted quickly.
Since the tool is stationary on a lathe, there is great flexibility for mounting the tool to best advantage. The tool post and carriage of a lathe provide several ways of positioning and feeding the tool. Below is shown the work area of an engine lathe.
The tool post is shown below. The tool post can pivot the tool about a vertical axis and the cutting tool can be moved in and out along its long axis. The cutting tool is held in by the vertical screws, the heads of which can be seen above the cutting tool groove.
Turning is another of the basic machining processes. Information in this section is organized according to the subcategory links in the menu bar to the left.
Turning produces solids of revolution which can be tightly toleranced because of the specialized nature of the operation. Turning is performed on a machine called a lathe in which the tool is stationary and the part is rotated. The figure below illustrates an engine lathe. Lathes are designed solely for turning operations, so that precise control of the cutting results in tight tolerances. The work piece is mounted on the chuck, which rotates relative to the stationary tool.
Turning
Turning refers to cutting as shown below.
The term "facing" is used to describe removal of material from the flat end of a cylindrical part, as shown below. Facing is often used to improve the finish of surfaces that have been parted.
Turning: Engine Lathe Detail
Engine Lathe Carriage
The figure below illustrates the carriage of an engine lathe. The carriage allows cross-feed and diagonal movements in addition to axial movement.
Turning: Chucks
The chuck is integral to a lathe's functioning because it fixtures the part to the spindle axis of the machine. Below is shown a three-jaw chuck with jaws that are all driven by the same chuck key. This arrangement provides convenience in that parts can be mounted and dismounted quickly.
Turning: Engine Lathe Tool Post
The cutting tool is fixtured on the tool post, which sits atop the carriage assembly. The carriage can move the tool post along the axis of part rotation, perpendicular to the axial direction, and on a diagonal.
The tool post is shown below. The tool post can pivot the tool about a vertical axis and the cutting tool can be moved in and out along its long axis. The cutting tool is held in by the vertical screws, the heads of which can be seen above the cutting tool groove.
Engine Lathe Tail Stock
The tail stock of an engine lathe is used to provide a fixture at the end of the part opposite from the chuck. The tail stock can be used to support a long, thin part so that more radial cutting force can be applied and higher rotational speeds can be attained without a "whipping" instability effect. Below is illustrated another use for the tail stock. Drill bits can be fixtured in the tail stock to cut axial holes in a turned part. These central holes are more accurate than a drill press or mill could provide since the lathe is dedicated to operations in which an axially-symmetric part is rotated about its central axis. The fixturing is more accurate since all fixturing is based upon surfaces of revolution about the central axis, and the machining is more rigidly supported for the same reason.
Boring
Boring can be accomplished on a mill or even a drill press, but is most accurate on a lathe. The boring tool is fixtured in the tail stock. Again, since all fixturing is relative to the central spindle axis, boring on a lathe is more accurate than most other boring methods, an exception being jig boring on a dedicated jig boring machine. The length of the boring bar is of critical importance because of its tendency to bend. The figure below illustrates a boring tool which is double-ended so that it is less prone to the cantilever "diving board" effect.
Turning: Standard Tool Post Tool
The tool inserted in the tool holder is shown below:
Knurling
Knurling is an operation used to produce a texture on a turned machine part. Handles are often knurled in order to provide a gripping surface. The two wheel inserts shown on the tool below contact the work piece, and with pressure, cold-form a pattern into the surface of the part.
Screw Machines
Screw machines are automated lathes which can quickly mass-produce turned parts. A screw machine uses cutting methods similar to that of a lathe but is highly automated. Screw machines are typically used for high-volume, low-cost turned parts. Feed stock for a screw machine is a long cylindrical rod of material. The screw machine automatically turns/faces the part, parts it off, and advances the rod for the next part. A screw machine is illustrated below.
Below is illustrated an on-axis view of how cross slides in a screw machine sequentially cut the work piece. Simultaneous action increases throughput. The view is down the axis of the spindle and shows how tools on cross slides can cut the work piece, some simultaneously with others.
The tail stock of an engine lathe is used to provide a fixture at the end of the part opposite from the chuck. The tail stock can be used to support a long, thin part so that more radial cutting force can be applied and higher rotational speeds can be attained without a "whipping" instability effect. Below is illustrated another use for the tail stock. Drill bits can be fixtured in the tail stock to cut axial holes in a turned part. These central holes are more accurate than a drill press or mill could provide since the lathe is dedicated to operations in which an axially-symmetric part is rotated about its central axis. The fixturing is more accurate since all fixturing is based upon surfaces of revolution about the central axis, and the machining is more rigidly supported for the same reason.
Boring can be accomplished on a mill or even a drill press, but is most accurate on a lathe. The boring tool is fixtured in the tail stock. Again, since all fixturing is relative to the central spindle axis, boring on a lathe is more accurate than most other boring methods, an exception being jig boring on a dedicated jig boring machine. The length of the boring bar is of critical importance because of its tendency to bend. The figure below illustrates a boring tool which is double-ended so that it is less prone to the cantilever "diving board" effect.
For design guidelines for bored holes in parts, please check the design for boring section.
Below are illustrated some of the many types of machining that can be accomplished on a lathe.
Turning: Standard Tool Post Tool
The tool inserted in the tool holder is shown below:
Single-Point Cutting Tool Variety
There are many types of cutting tools for different operations. Below is shown a few of the variety, here shown with a tool holder adapter that fits into a larger tool post fixture.
Below is shown how single-point lathe tools can be used.
Parting Tool
The illustration below shows how a parting tool is fixtured and used. Parting is important at the end of a turning process in order to separate the part from the raw material. Parting must be carried out slowly and carefully since the tool is quite long and is prone to chattering. Parting is not very accurate, and a finishing cut must often be undertaken after parting if the parted surface is to be accurate.
There are many types of cutting tools for different operations. Below is shown a few of the variety, here shown with a tool holder adapter that fits into a larger tool post fixture.
Below is shown how single-point lathe tools can be used.
Parting Tool
The illustration below shows how a parting tool is fixtured and used. Parting is important at the end of a turning process in order to separate the part from the raw material. Parting must be carried out slowly and carefully since the tool is quite long and is prone to chattering. Parting is not very accurate, and a finishing cut must often be undertaken after parting if the parted surface is to be accurate.
Knurling
Knurling is an operation used to produce a texture on a turned machine part. Handles are often knurled in order to provide a gripping surface. The two wheel inserts shown on the tool below contact the work piece, and with pressure, cold-form a pattern into the surface of the part.
Screw Machines
Screw machines are automated lathes which can quickly mass-produce turned parts. A screw machine uses cutting methods similar to that of a lathe but is highly automated. Screw machines are typically used for high-volume, low-cost turned parts. Feed stock for a screw machine is a long cylindrical rod of material. The screw machine automatically turns/faces the part, parts it off, and advances the rod for the next part. A screw machine is illustrated below.
Cross Slide Simultaneous Operation |
>