MPL 1 (MET 1321) Prof. Simin Nasseri Manufacturing Processes lab I Running a lathe machine

MPL 1 (MET 1321)Prof. Simin Nasseri

Manufacturing Processes lab I

Running a lathe machine


MachiningMachining – material removal by a sharp cutting

tool, e.g., turning, milling, drilling

Cutting action involves shear deformation of work material to form a chip. (As chip is removed, new surface is exposed)


Turning Turning refers to cutting as shown in this figure.

Single point cutting tool removes material from a rotating workpiece to form a cylindrical shape.


Cutting Conditions for Turning

Speed, feed, and depth of cut in turning.


Schematic diagram of the lathe machine


Turning: Engine Lathe Turning is another of the basic machining processes.

Turning is performed on a machine called a lathe in which the tool is stationary and the part is rotated.


Turning: Engine Lathe

The figure 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.


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.


ChucksThe 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.

3 and 4-jaws chuck: It is easier to align the work piece axis with the lathe axis which has 4 jaws chuck.


Engine Lathe Tail Stock


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.


Engine Lathe Tail StockDrill 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.


Tool postThe cutting tool is fixed on the tool post, which sits atop the carriage assembly. As mentioned, the carriage can move the tool post along the axis of part rotation, perpendicular to the axial direction, and on a diagonal.

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.


ToolThe tool inserted in the tool holder is shown below:


Tool post

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.


Turret tool postThis tool post can hold many tool bits at the same time. Each cutting tool can quickly be swiveled into cutting position and clamped into place using a quick clamping handle.


Parting Tool This figure shows how a parting tool is fixed 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 vibrating. Parting is not very accurate, and a finishing cut must often be undertaken after parting if the parted surface is to be accurate.


FacingThe 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.

Tool is fed radially inward


ThreadingPointed form tool is fed linearly across surface of

rotating workpart parallel to axis of rotation at a large feed rate, thus creating threads


Reaming

Used to slightly enlarge a hole, provide better tolerance on diameter, and improve surface finish


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.


Knurling


BoringThe boring tool is fixed in the tail stock. Boring can be accomplished on a mill or even a drill press, but is most accurate on a lathe, because the fixturing is relative to the central spindle axis

Boring is rather well named... its, urm, quite boring. Essentially you have to drill a hole into the job with your biggest drill bit - Then you have to mount the boring tool on the tool post so that it is parallel to the ways. Then you use the tools to slowly increase the inside diameter of the job to the size you require. The most you can take off in each pass is about 0.5mm - so it can take a long time to make a 2 inch bore hole!


Boring

The length of the boring bar is of critical importance because of its tendency to bend.


Turning categoriesBelow are illustrated some of the many types of machining that can be accomplished on a lathe.


Turning categories


Single-Point Cutting Tool Variety

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.


Single-Point Cutting Tool VarietyBelow is shown how single-point lathe tools can be used.


Test yourself!

Turning is performed on a machine called a lathe in which the part is stationary and the tool is rotated.– True – False

You mount your work piece inside the chuck not a tail stock.– True – False


Test yourself!

Which part of lathe machine is this?

Chuck


Test yourself!Which operation is shown here:

Boring


Test yourself!

Which operation is this?

Tool is fed radially inward

Facing


Test yourself!

What is the name of this operation:

knurling


Test yourself!

Name different operations shown here:

Boring

Facing

parting

Documents

MPL 1 (MET 1321) Prof. Simin Nasseri Manufacturing Processes lab I Running a lathe machine