Cutting_Speed_Feed_and_DOC
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feed = .020
length of cut 16 Roughing cut time 4.4 min feed x r/min .020 x 180 100 x 4 Finishing cut: RPM 216 1.850 Total Time
5
Example:
Calculate RPM required to rough-turn 50 mm diameter piece of machine steel (CS 27 MPM):
CS x 320 RPM D 27 x 320 RPM 172.8 50
6
Lathe Feed
8
Lathe Feedrates
High-speed steel cutting tool feedrate per revolution of spindle
Rough Cuts Material Mach steel Tool steel in. mm in. .010–.020 0.25–0.5 .010–.020 0.25–0.5 Finish Cuts mm .003–.010 0.07–0.25 .003–.010 0.07–0.25
10
Depth of cut on a lathe
11
Factors Determining Depth of Rough-Turning Cut
• Available Stock
• Workpiece Material • Condition of machine • Type and shape of cutting tool used • Rigidity of workpiece, machine, and cutting tool • Rate of feed
CS x 12 CS x 4 RPM D D
4
Example:
Calculate RPM required to rough-turn 2 in. diameter piece of machine steel (CS 90 SFM):
CS x 4 RPM D 90 x 4 RPM 180 2
• Inch system graduated in .001 inch • Metric system usually in steps of 0.02 mm
13
Graduated Micrometer Collars
14
Inch System
• Circumference of crossfeed and compound rest screw collars divided into 100-125 equal divisions
• Too high: cutting-tool breaks down rapidly • Too low: time lost, low production rates
2Байду номын сангаас
Lathe Cutting Speeds
Using High-Speed Steel Toolbit
Turning and Boring Rough Cut Finish Cut Material Mach steel Tool steel Cast iron Bronze Aluminum 90 70 60 90 200 27 21 18 27 61 100 90 80 100 300 30 27 24 30 93 Threading 35 30 25 25 60 11 9 8 8 18
•
•
•
•
Make sure collar is secure before setting a depth of cut All depths of cut must be made by feeding cutting tool toward workpiece If graduated collar turned past desired setting, must be turned backward halfturn and fed into proper setting to remove backlash Never hold graduated collar when setting depth of cut
• Each has value of .001 inch
• Turn crossfeed screw clockwise 10 graduations, cutting tool moved .010 inch toward work • Lathe revolves, so .010 depth of cut taken from entire work circumference reducing diameter .020 inch
• Distance cutting tool advances along length of work for every revolution of the spindle • Feed of engine lathe dependent on speed of lead screw for feed rod
• • • Set compound rest to 84º 16' to the cross-slide .001 in movement = .0001 infeed movement .02 mm movement = .002 infeed movement
20
Calculating Machining Time
Compound rest swung to 30º , amount removed from length of work = ½ amount of feed on collar
19
•
Facing
•
Graduated Collar Use
• Machining accurate diameters
• .010- to .015-in. (0.25- to 0.4-mm)
• Finishing cut
• Used to bring diameter to size • Fine feed: Produce good finish
• .003- to .005-in (0.07- to 0.012-mm)
3
ft/min m/minft/min m/minft/min m/min
Calculating Spindle Speed
• Given in revolutions per minute • Cutting speed of metal and diameter of work must be known • Proper spindle speed set by dividing CS (in/min) by circumference of work (in)
• Depth of chip taken by cutting tool and one-half total amount removed from workpiece in one cut • Only one roughing and one finishing cut
• Roughing cut should be deep as possible to reduce diameter to within .030 to .040 inch or .75 to 1 mm of size required • Finishing cut should not be less than .005 inch or .125 mm
Cutting Speed, Feed, and Depth of Cut
Session 8
1
Cutting Speed
• Rate at which point on work circumference travels past cutting tool • Always expressed in feet per minute (ft/min) or meters per minute (m/min) • Important to use correct speed for material
• Factors such as spindle speed, feed and depth of cut must be considered
distance Time rate Where distance length of cut rate feed x RPM
21
Example:
12
Graduated Micrometer Collars
• Used when diameter of work must be turned to accurate size • Sleeves or bushings mounted on compound rest and crossfeed screws • Measurement
15
Metric System
• Circumference of crossfeed and compound rest screw collars divided into 100-125 equal divisions
• Each has value of .02 mm
• Turn crossfeed screw clockwise 10 graduations, cutting tool moved .2 mm toward work • Lathe revolves, so .2 mm depth of cut taken from entire work circumference reducing diameter .4 mm
• Speed controlled by change gears in quick-change gearbox
7
Bringing Diameter to Size Using Two Cuts
• Roughing cut
• Purpose to remove excess material quickly • Coarse feed: surface finish not too important
Cast iron
Bronze . Aluminum
.015–.025 0.4–0.65
015–.025 0.4–0.65 .015–.030 0.4–0.75
.005–.012 0.13–0.3
.003–.010 0.07–0.25 .005–.010 0.13–0.25
9
Depth of Cut
18
Graduated Collar Use
•
•
Graduated collar on compound rest can be used for accurately setting depth of cut
Shoulder turning
• • • Compound rest set at 90ºto cross-slide Lock carriage in place Spacing of shoulders to within .001 in. accuracy
16
On machines where the workpiece revolves, the cutting tool should be set in for only half the amount to be removed from the diameter.
17
Graduated Collar Use
Calculate the time required to machine a 2-in. diameter machine-steel shaft 16 inch to 1.850 diameter finish size Roughing cut Roughing feed
CS x 4 90 x 4 RPM 180 D 2
length of cut 16 Roughing cut time 4.4 min feed x r/min .020 x 180 100 x 4 Finishing cut: RPM 216 1.850 Total Time
5
Example:
Calculate RPM required to rough-turn 50 mm diameter piece of machine steel (CS 27 MPM):
CS x 320 RPM D 27 x 320 RPM 172.8 50
6
Lathe Feed
8
Lathe Feedrates
High-speed steel cutting tool feedrate per revolution of spindle
Rough Cuts Material Mach steel Tool steel in. mm in. .010–.020 0.25–0.5 .010–.020 0.25–0.5 Finish Cuts mm .003–.010 0.07–0.25 .003–.010 0.07–0.25
10
Depth of cut on a lathe
11
Factors Determining Depth of Rough-Turning Cut
• Available Stock
• Workpiece Material • Condition of machine • Type and shape of cutting tool used • Rigidity of workpiece, machine, and cutting tool • Rate of feed
CS x 12 CS x 4 RPM D D
4
Example:
Calculate RPM required to rough-turn 2 in. diameter piece of machine steel (CS 90 SFM):
CS x 4 RPM D 90 x 4 RPM 180 2
• Inch system graduated in .001 inch • Metric system usually in steps of 0.02 mm
13
Graduated Micrometer Collars
14
Inch System
• Circumference of crossfeed and compound rest screw collars divided into 100-125 equal divisions
• Too high: cutting-tool breaks down rapidly • Too low: time lost, low production rates
2Байду номын сангаас
Lathe Cutting Speeds
Using High-Speed Steel Toolbit
Turning and Boring Rough Cut Finish Cut Material Mach steel Tool steel Cast iron Bronze Aluminum 90 70 60 90 200 27 21 18 27 61 100 90 80 100 300 30 27 24 30 93 Threading 35 30 25 25 60 11 9 8 8 18
•
•
•
•
Make sure collar is secure before setting a depth of cut All depths of cut must be made by feeding cutting tool toward workpiece If graduated collar turned past desired setting, must be turned backward halfturn and fed into proper setting to remove backlash Never hold graduated collar when setting depth of cut
• Each has value of .001 inch
• Turn crossfeed screw clockwise 10 graduations, cutting tool moved .010 inch toward work • Lathe revolves, so .010 depth of cut taken from entire work circumference reducing diameter .020 inch
• Distance cutting tool advances along length of work for every revolution of the spindle • Feed of engine lathe dependent on speed of lead screw for feed rod
• • • Set compound rest to 84º 16' to the cross-slide .001 in movement = .0001 infeed movement .02 mm movement = .002 infeed movement
20
Calculating Machining Time
Compound rest swung to 30º , amount removed from length of work = ½ amount of feed on collar
19
•
Facing
•
Graduated Collar Use
• Machining accurate diameters
• .010- to .015-in. (0.25- to 0.4-mm)
• Finishing cut
• Used to bring diameter to size • Fine feed: Produce good finish
• .003- to .005-in (0.07- to 0.012-mm)
3
ft/min m/minft/min m/minft/min m/min
Calculating Spindle Speed
• Given in revolutions per minute • Cutting speed of metal and diameter of work must be known • Proper spindle speed set by dividing CS (in/min) by circumference of work (in)
• Depth of chip taken by cutting tool and one-half total amount removed from workpiece in one cut • Only one roughing and one finishing cut
• Roughing cut should be deep as possible to reduce diameter to within .030 to .040 inch or .75 to 1 mm of size required • Finishing cut should not be less than .005 inch or .125 mm
Cutting Speed, Feed, and Depth of Cut
Session 8
1
Cutting Speed
• Rate at which point on work circumference travels past cutting tool • Always expressed in feet per minute (ft/min) or meters per minute (m/min) • Important to use correct speed for material
• Factors such as spindle speed, feed and depth of cut must be considered
distance Time rate Where distance length of cut rate feed x RPM
21
Example:
12
Graduated Micrometer Collars
• Used when diameter of work must be turned to accurate size • Sleeves or bushings mounted on compound rest and crossfeed screws • Measurement
15
Metric System
• Circumference of crossfeed and compound rest screw collars divided into 100-125 equal divisions
• Each has value of .02 mm
• Turn crossfeed screw clockwise 10 graduations, cutting tool moved .2 mm toward work • Lathe revolves, so .2 mm depth of cut taken from entire work circumference reducing diameter .4 mm
• Speed controlled by change gears in quick-change gearbox
7
Bringing Diameter to Size Using Two Cuts
• Roughing cut
• Purpose to remove excess material quickly • Coarse feed: surface finish not too important
Cast iron
Bronze . Aluminum
.015–.025 0.4–0.65
015–.025 0.4–0.65 .015–.030 0.4–0.75
.005–.012 0.13–0.3
.003–.010 0.07–0.25 .005–.010 0.13–0.25
9
Depth of Cut
18
Graduated Collar Use
•
•
Graduated collar on compound rest can be used for accurately setting depth of cut
Shoulder turning
• • • Compound rest set at 90ºto cross-slide Lock carriage in place Spacing of shoulders to within .001 in. accuracy
16
On machines where the workpiece revolves, the cutting tool should be set in for only half the amount to be removed from the diameter.
17
Graduated Collar Use
Calculate the time required to machine a 2-in. diameter machine-steel shaft 16 inch to 1.850 diameter finish size Roughing cut Roughing feed
CS x 4 90 x 4 RPM 180 D 2