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AIM – to determine the MRR and depth of cut for a given round shape job by using lathe machine

Apparatus required –

Power supply , veriner scale , lathe machine , work piece. Digital tacometre 1

Theory –

- MRR (material removal rate )

Material removal rate (MRR) is the amount of material removed per time unit (usually per minute)
when performing machining operations such as using a lathe or milling machine. The more material
removed per minute, the higher the material removal rate.[

MRR= Ap *Fn*Vc

Where,

Ap – Depth of cut in mm or inches.

Fn – Feed rate n in mm or inches.

Vc – Cutting Speed in( m/min )or(

feet/min) (SFM).

MRR – Metal Removal Rate in CM3/min or

Inch3/min

- Depth of cut
Initial diameter – final diameter/2
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The depth of cut in lathe machining refers to the measurement of the amount of material
that is being removed from the workpiece during each pass of the cutting tool. It is an
important parameter that determines the efficiency and accuracy of the machining process.
- Cutting speed

It is the speed at which the metal is removed by the cutting tool from the workpiece. In the case of
lathe machine cutting speed is the peripheral speed of the work past the cutting tool. It is expressed
in meter/min. or mm/min.

Cutting speed = π DN/60 × 1000 mm/min

Where

D = diameter of the workpiece (mm)

N = rpm of the work

- Feed rate (fn)

Feed rate is the linear velocity at which the cutting tool moves
relative to the workpiece.The feed rate is what determines how
quickly the material is removed.

• Units: (mm/min).

fm=f×N

• fm = Feed Rate (in/min or mm/min)

• f = Feed (in/rev or mm/rev)

• N = Spindle Speed (RPM)

- Feed

feed per revolution, is the distance a cutting tool advances for each
complete rotation of the workpiece or the cutting tool.

• Units: (mm/rev).

Formula f=fm/N

• f = Feed (in/rev or mm/rev)

• fm = Feed Rate (in/min or mm/min)

• N = Spindle Speed (revolutions per minute, RPM)

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Machine time-

The machining time in the lathe work can be calculated for a particular operation if the
speed of the job, feed and length of the job is known.

Procedure

Step 1 Workpiece Mounting: The first step is to securely clamp the workpiece in the lathe chuck or
between the centers. It must be rigid and centered to prevent wobbling or vibration during the cut.

Step 2 Tool Selection: Choose the appropriate cutting tool for the job. Roughing tools are used for
initial material removal, while finishing tools are used for the final, smooth surface.

Step 3 Tool Mounting: Mount the selected cutting tool in the tool post. The cutting edge must be
aligned precisely with the center height of the workpiece. Improper alignment can lead to poor
surface finish, tool chatter, or even tool breakage.

Step 4 Safety Checks: Before starting the machine, ensure all guards are in place, the work area is
clear of debris, and you are wearing appropriate personal protective equipment (PPE).

Step 5 Set Machining Parameters: Set the spindle speed (RPM) and feed rate (in/min or mm/min)
based on the workpiece material, tool material, and desired surface finish.

Step 6 Position the Tool: Manually or via the control panel, move the cutting tool to the starting
position. For a turning operation, this is typically at the end of the workpiece, slightly away from the
face.

Step 6 Give Depth of Cut: Carefully advance the cross-slide to set the depth of cut. This determines
how much material will be removed in a single pass. A larger depth of cut means faster material
removal but requires more power and can put more stress on the tool and machine.

Step 7 Engage Spindle: Start the lathe spindle, causing the workpiece to rotate at the set RPM.
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Step 8 Engage Feed: Engage the longitudinal feed, which moves the tool along the length of the
workpiece at the set feed rate.

Step 9 Monitor: As the tool cuts, watch the process closely for any signs of chatter, smoke, or
excessive tool wear.

Step 10 Repeat Passes: Once the tool reaches the end of the desired cut length, retract the tool
and return the carriage to the starting position. Take another depth of cut and repeat the process
until the workpiece reaches the final, desired diameter.

Step 11 Finish Pass: For the final pass, use a smaller depth of cut and a higher spindle speed to
achieve a better surface finish.

Step 12 Measure: After completing the machining, turn off the lathe and use a micrometer or
caliper to measure the diameter and length of the workpiece to verify that it is within the specified
tolerances.

Step 13 Clean Up: Clean the machine and the workpiece, removing all chips and coolant.

Step 14 Remove Workpiece: Carefully remove the finished workpiece from the chuck

Precautions-

◼ Lathe mic should be handle carefully

◼ Use Tachometer carefully

◼ Reading should be accurate

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