Manufacturing Processes lab I Running a lathe machine-2

MPL I (MET 1321) Prof. Simin Nasseri

Cutting speeds and feeds

These factors govern the length of time required to machine the work and the quality of the surface finish.

MPL I (MET 1321) Prof. Simin Nasseri

Various Cuts

Roughing cuts are taken to reduce work diameter to approximate size. The work is left 1/32” (0.08 mm) oversize for finish turning. (use the highest speed and coarsest feed consistent with safety and accuracy).

Finishing cut finish. A high-spindle speed, sharp cutting tool and fine feed are employed.

brings the work to the required diameter and surface

MPL I (MET 1321) Prof. Simin Nasseri

Cutting Speed

Cutting speed , indicates the distance the work moves past the cutting tool, expressed in feet per minutes (fpm) or meters per minutes (mpm).

In fact, the length of the chip cut in one minute (in feet or meters) would be the cutting speed of the lathe.

Cutting speed is not the revolutions per minute (rpm) of the lathe.

MPL I (MET 1321) Prof. Simin Nasseri

Cutting Feed

Feed is the distance that the cutter moves length-wise along the lathe bed during a single revolution of the work.

Cutting speeds and feeds suggested for turning various metals with high-speed steel tools.

These speeds will be increased by 50% if a coolant is used, and by 300% to 400% if a cemented carbide cutting tool is employed.

MPL I (MET 1321) Prof. Simin Nasseri

Calculating cutting speeds

Cutting speed (CS) is given in feet per minute (fpm) or meters per minute (mpm).

Speed of the work minute (rpm).

(Spindle speed) is given in revolutions per The peripheral speed the work) must be converted to rpm to determine the required spindle speed.

(speed at the circumference or outside edge of INCH-BASED: rpm= = π D D

CS=Cutting Speed, in feet/min D= Diameter of work in inches Convert all fractions to decimals Round π to 3

MPL I (MET 1321) Prof. Simin Nasseri

Calculating cutting speeds

What spindle speed is required to finish-turn 8” diameter aluminum alloy?

rpm= (CSx 4/D)= 1000”x4/8= 500 rpm So adjust the spindle speed to as close to 500rpm as possible. Increase or decrease speed as needed to obtain desired surface finish.

MPL I (MET 1321) Prof. Simin Nasseri

Calculating cutting speeds

METRIC-BASED: rpm= CS x 1000 π D CS=Cutting Speed in meter/min D= Diameter of work in milimeter round π to 3 What spindle speed is required to finish-turn 100 mm diameter aluminum alloy?

rpm= (300mpmx 1000)/ (100 π)= 3000/3= 1000 rpm

MPL I (MET 1321) Prof. Simin Nasseri

Depth of Cut

The depth of cut refers to the distance the cutter is fed into the work surface. The depth of cut, like feed, varies greatly with lathe condition, material hardness, speed, feed, amount of material to be removed and whether it is to be a roughing or finishing cut.

Depth of cut can be set accurately with the Micrometer dials slide and compound rest.

on the cross-

MPL I (MET 1321) Prof. Simin Nasseri

Depth of Cut

The micrometer dial is usually of the rotating work at

double

graduated in 0.001” or 0.02mm increments .

This means that a movement of one graduation feeds the cutting tool into the piece 0.001” or 0.02mm. However, material is removed around the periphery (outside edge) the depth adjustment.

MPL I (MET 1321) Prof. Simin Nasseri