Preparing a cylindrical job as per given diagram by different operations in Lathe machine tool like Step Turning, Grooving, Chamfering and Threading

  • Objectives:
  1.  To acquaint the student with the functioning of the machine tool (Lathe).
  2. To develop the confidence in the different operation of the machine tool.
  3. To know the various accessories of the machine, cutting tools and measuring instruments along with their specifications.
  • Theory:

The lathe is a machine tool used principally for shaping articles of metal, wood, or other material. The lathe is one of the machine tools most widely used for machining. Lathe removes undesired material from a rotating work piece in the form of chips with the help of a tool which is traversed across the work and can be fed deep in work. Lathe machine holds the work piece between two rigid and strong supports called Centers, or in a Chuck or Face plate while the latter revolves. The chuck or the face plate is mounted on the projected end of the machine spindle. The cutting tool is rigidly held and supported in a tool post and is fed against the revolving work. While the work revolves about its own axis the tool is made to move either parallel to or at an inclination with this axis to cut the desired material. In doing so it produces a cylindrical surface, if it is fed parallel to the axis or will produced a Tapered surface if it is fed at an inclination. The typical lathe provides a variety of rotating speeds and suitable manual and automatic control for moving the cutting tool. 

  • Drawing of the job:

                       

  • List of equipments used:
  1.  Lathe machine with all its accessories.
  2. Single point cutting tool and other tools as per requirement. 
  • List of Tools used:
  1. Cutting Tools used
  2. Turning Tool
  3. Parting Tool
  • Threading tool:
  1.  Measuring Tools used
  2. Outside caliper
  3. Steel scale
  4. Vernier caliper
  • Raw Material:

Raw Material metal:Size: Ф 32 mm x 115 mm long.

  • Working Procedure: 

A) Preparatory 

  1. Collect and check the raw material for shape and dimensions.
  2. Collect the cutting tool and measuring tools.
  3. Check the specifications of the lathe, cutting tools and measuring tools.
  4. Load the job on the lathe chuck and centre it properly by manually rotating the chuck and correcting the eccentricity.
  5. Fix the cutting tool on the tool post with the tool tip at the centre of rotation.
  6. Select the speed, feed and depth of cut.
  7. Determine the desired speed (rpm) and select the nearest speed (rpm) from the available machine speeds.
  8. Acquaint with starting and stopping procedure, operating levers/knobs of the lathe. Beware of the dangers associated with the operation.

B) Operation

  1. Perform the rough turning operation up to desired length with a small depth of cut..
  2. Perform the further operation to required diameter.
  3. Do step turning up to desired length to required diameter.
  4. Continue machining till final diameter being achieved.
  5. Make the chamfer.
  6. Perform grooving operation by using parting tool.
  7. Perform the threading operation by selecting threading tool and changing the gear arrangement considering thread chart.
  8. Stop the operation, unclamp the workpiece and fix other end of the workpiece to the chuck.
  9. Perform the rough turning operation up to desired length with a small depth of cut.
  10. Perform the further operation to final diameter.
  11. Perform facing operation.
  12. Stop the operation, clean the machine and return the cutting tools and measuring tools after the measurements.
  13. Finally measure the dimensions (length and diameter) of the job write down the measured data in the observation table.
  • Sequence of Operations: 

Turning ⟶  Step Turning (upto Ø 28 mm, Length 65 mm)  ⟶ Step Turning (upto Ø 16 mm, Length 35 mm)⟶   Chamfering ⟶ Grooving  ⟶  threading ⟶ Turning (other end upto Ø 30 mm length 45 mm) ⟶ Facing          

  • Observation Table:
Sl. No. Particulars Required dimensions (mm) Measured dimension (mm) Variation (mm) Remarks
1 Length 40      
2 Length 30      
3 Length 5      
4 Length 30      
5 Diameter (Φ) 30      
6 Diameter (Φ) 25      
7 Diameter (Φ) 11      
8 Pitch 2      
  • Discussion: 
  • Safety Precautions:
  1. When working with a lathe, following precautions are to be adopted
  2. Must protect eyes from the high quantity of sharp debris/chips that flies off the lathe during turning.
  3. Take proper safe distance or wear eye protection.
  4. Do not wear loose garments as loose items can get caught in rotating parts and result in serious injury.
  5. If the workpiece vibrates, this is an indication that the speed is too fast, reduce the speed until the workpiece rotates steadily without vibration.
  6. Turn off the power and wait until the lathe comes to a full stop when mounting or removing accessories.
  7. The floor should be free from grease, oil, which can cause someone to slip or trip.
  8. Lathe should not be operated without the working knowledge of it and in the absence of instructor.
  9. The lathe motor should always be turned off before adjusting the tool rest or any other parts, or before cleaning, lubricating, or measuring.

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