Conventional Lathe

Lesson Outcomes

By the end of this lessons, students should be able to:

• The concept of lathe and different lathe operations

• Calculating machining parameters in lathe

operations

• Lathe machine components and lathe cutting tool

• Design and operating guideline for lathe

operations as well as troubleshooting

• Current developments in lathe machining

Lathe concept

Lathe: A machining process whereby a cutting

tool is fed into a rotating workpiece

Turning-Cutting primarity

along axial direction

Lathe-Cutting primarily

along radial direction

Lathe / turning

workpiece

Cutting

tool

workpiece

Cutting

tool

Types of lathe operations

Pls read & understand descriptions of each operation in 674-676

Types of lathe operations

1. Turning: to produce straight, conical, curved, or grooved workpieces such as shafts, spindles, and pins.

2. Facing: to produce a flat surface at the end of the part and perpendicular to its axis useful for parts that are assembled with other components.

3. Cutting with form tools: to produce various axisymmetric shapes for functional or aesthetic purposes.

4. Boring: to enlarge a hole or cylindrical cavity made by a previous process or to produce circular internal grooves.

5. Drilling: to produce a hole which may be followed by boring to improve its dimensional accuracy and surface finish.

Types of lathe operations

6. Parting: also called cutting off, to cut a piece

from the end of a part, as is done in the

production of slugs or blanks for additional

processing into discrete products

7. Threading: to produce external or internal

threads

8. Knurling: to produce a regularly shaped

roughness on cylindrical surfaces, as in making

knobs

Roughing & Finishing

1. Perform rough cut: high f,d high MRR.

Why?

2. Perform finishing cut: low f,d low

MRR. Why?

Recommendations for

turning parameters

Lathe machine

Lathe machine components

Bed: supports all other major components. Heavy & rigid. Ways allows carriage to slide.

Carriage: consists of cross-slide, tool post, and apron. Cutting tool is mounted on tool post.

Cross slide: moves radially and in/out.

Headstock: Contains motors & gearing to supply power to spindle.

Spindle: hollow so that a workholding device (chuck or collet can be mounted)

Tailstock: Slides in the ways to support the other end of the workpiece. Dead/live center or drill can be mounted here.

Troubleshooting lathe operations

High speed machining

• High speed: V=600-1800 m/min

• Very high speed: V=1800-18000 m/min

• Ultra high speed: V>18000 m/min

• Heat is removed along with chips low

thermal distortion

• High productivity Low unit cost

Ultra precision machining

• For precision manufacturing of electronic,

nuclear energy and defense applications

• Cutting tool is a single crystal diamond

• Tool radius is at nanometer (10-9) level

• Surface finish is at nanometer level

• Very stiff machines with temperature

stability

Summary

• Lathe is a process whereby a cutting tool is fed into a rotating workpiece. A number of lathe processes allows the machinist to machine a great variety of cylindrical shapes

• Calculations for Material removal rate, cutting speed, cutting time, torque and power are important before any lathe operation

• Components should be designed with machining limitations in mind

• Troubleshooting can be performed by identifying the appropriate machining parameter to change and modifying it in the correct amount

• High speed machining and precision machining are becoming increasingly important to lower production cost and produce precision components