CS-1
Cutting Speeds
Feeds and Speeds
Production on drills, mills, lathes, grinders, and other machine tools depends on the rate
of relative motion between the cutter or grinding wheel and the workpiece. Gears roll together, there
is no relative rotation speed difference where teeth mesh. There must be a difference for cutting to take
place. The amount of this difference is called SFM or SFPM (Surface Feet Per Minute).
When the workpiece or tool, or both, rotate, the difference in speeds at the contacting surface can be calculated
from the RPM (Revolutions Per Minute). Because of the many variables in equipment and tool condition, actual
speeds may vary. Speeds and Feeds should be as high as practical in order to provide an adequate rate of
Production.
Practical limits are set by finish requirements, power available, rigidity of the workpiece, the machine tool,
and by expected tool life. When the finish is satisfactory, power is sufficient, no present threat of distortion,
no burning or breaking, and the tool life is satisfactory, then the speed and feed are not too high.
Whenever chatter indicates an incorrect speed or feed, higher as well as lower speeds or feeds
should be tried. In feed is the name given to feed that is in the plane of rotation of the cutter or workpiece
on mills, lathes, and grinders, into the work. The greater the In Feed, the greater the depth of cut.
On drills and surface grinders In Feed is called Down-feed because of it's direction.
Cross - Feed is feed perpendicular to the plane of rotation of the workpiece, cutter, or grinding wheel.
On a lathe it is set in a number of thousands of an inch per revolution of the workpiece. On surface grinders
and mills, it is made by movement of the saddle, perpendicular to the table movement, but in the same X, Y, plane.
Cross feed on all machines is mainly limited by tool life and surface finish. Cross feed should be as high as
finish requirements and reasonable tool life will allow.
The forces at work in machining are by far highest in those interactions due to relative rotation.
In feed and cross feed are also factors, but secondary ones. Once appropriate SFPM has been established
for the machine tool, and workpiece, correct in feed and cross feed can quickly be made.
Turning SFPM
The diameter of a round piece of work is the largest measurement perpendicular to the axis across the work.
In order to find the distance that passes the tool point in one revolution, the diameter is multiplied by 3.14.
This distance is called the circumference . The diameter is given in inches, therefore the circumference is in inches.
CS-2
Cutting Speeds
(Recommended Surface Feet Per Minute)
Material
High Speed
Steel
Rough
Finish
Carbide -- Tipped
Rough
Finish
Coolant
Cast Iron
50-60
80-110
180-200
350-400
Dry
Semi-Steel
40-50
65-90
140-160
250-300
Dry
Malleable Iron 80-100
110-130
250-300
400-500
Soluble, Sulphurized
Mineral Oil
Cast Steel
45-60
70-90
150-180
200-250
Soluble, Sulphurized,
Mineral or Mineral Lard Oil
Copper
100-150
150-200
600
1000
Soluble, Sulphurized,
or Mineral Lard Oil
Brass
200-300
200-300
600-1000
600-1000
Bronze
100-150
150-180
600
1000
Soluble, Sulphurized,
or Mineral Lard Oil
700
800
1000
Soluble or Sulphurized Oil
Mineral Oil and Kerosene
Aluminum
Magnesium
400
600-800
1000-1500
1000-1500
1000-1500
Dry
Dry, Kerosene, or
Mineral Lard Oil
SAE Steels
1020
60-80
Course Feed
60-80
300
300
1020
Fine Feed
100-120
100-120
450
450
"
"
1035
75-90
90-120
250
250
"
"
1050
60-80
100
200
200
"
"
3150
50-60
70-90
200
200
"
"
4340
40-50
60-70
200
200
240-300
240-300
Stainless Steel 60-80
100-120
Soluble, Sulphurized
Mineral, or Mineral Lard Oil
Sulphurized and Mineral Oils
"
"
CS-3
CS-4
Cutting Speeds
Definition of Cutting Speed
Cutting speed is the rate at which a point on the circumference of a cylindrical workpiece passes a cutting tool.
Cutting speeds are given in Feet Per Minute, while spindle speed is given in Revolutions Per Minute , thus the
peripheral speed of the workpiece (speed at circumference) must be converted to Revolutions Per Minute (RPM)
in order to determine the required spindle speed.
The following formula is used;
RPM = C.S. x 4
D
Example:
Legend
C.S. = Cutting Speed
D = Workpiece or Cutter Dia.
Machine a workpiece 3/4" in diameter from Stainless Steel.
1.
RPM = C.S. x 4
D
2.
R.P.M. = 40 x 4
.75
3.
R.P.M.
160
.75
4.
R.P.M. =
213
CS-5
Cutting Speeds For Various Diameters
The following chart revolutions are based on the formula;
CS x 12
RPM= -------------------x D
Meters Per
Minute
Feet Per
Minute
Diameter
mm
Inches
1.6
1/16
3.2
1/8
4.8
3/16
6.4
1/4
7.9
5/16
9.5
3/8
11.1 7/16
12.7 1/2
15.9 5/8
19.1 3/4
22.2 7/8
25.4 1.0
28.6 1 1/8
31.8 1 1/4
34.9 1 3/8
38.1 1 1/2
41.3 1 5/8
44.5 1 3/4
47.6 1 7/8
50.8 2.0
57.2 2 1/4
63.5 2 1/2
69.9 2 3/4
76.2 3.0
15.2
18.3
21.3
24.4
27.4
30.5
33.5
36.6
39.6
42.7
45.7
61
50'
60'
70'
80'
90'
100'
110'
120'
130'
140'
150'
200'
4889
2445
1630
1222
978
815
698
611
489
407
349
306
272
244
222
204
188
175
163
153
136
122
111
102
Revolutions Per Minute
5500 6111 6722
2750 3056 3361
1833 2037 2241
1375 1528 1681
1100 1222 1345
917
1019 1120
786
873
960
688
764
840
550
611
672
458
509
560
393
436
480
344
382
420
306
340
373
275
306
336
250
278
306
229
255
280
212
235
259
196
218
240
183
204
224
172
191
210
153
170
187
137
153
168
125
139
153
115
127
140
7334
3667
2445
1833
1467
1222
1048
917
733
611
524
458
407
367
333
306
282
262
244
229
204
183
167
153
7945
3973
2648
1986
1589
1324
1135
993
794
662
568
497
441
397
361
331
306
284
265
248
221
199
181
166
8556
4278
2852
2139
1711
1426
1222
1070
856
713
611
535
475
428
389
357
329
306
285
267
238
214
194
178
9167 12229
4584 6115
3056 4076
2292 3057
1833 2446
1528 2038
1310 1747
1146 1529
917
1223
764
1019
655
874
573
764
509
679
458
612
417
556
382
510
353
470
327
436
306
408
287
382
255
340
229
306
208
278
191
254
3056
1528
1019
764
611
509
437
382
306
255
218
191
170
153
139
127
117
109
102
95
85
76
69
64
3667
1833
1222
917
733
611
524
458
367
306
262
229
204
183
167
153
141
131
122
115
102
92
83
76
4278
2139
1426
1070
856
713
611
535
428
357
306
267
238
214
194
178
165
153
143
134
119
107
97
89
94.1
300'
18344
9172
6115
4586
3669
3057
2621
2293
1834
1529
1310
1146
1019
918
834
765
705
654
612
573
510
459
417
381
CS-6
Cutting Speeds
Cutting, Rim, and Surface Speed Formula's
C.S. = Cutting Speed
R.S. = Rim Speed
S.S. = Surface Speed
= 3.1416
R.P.M. = Revolutions Per Minute
D
= Diameter of Workpiece or Milling Cutter
C.S. = D x RPM
12
RPM = CS x 12
D
R.S. = D x RPM
12
RPM = RS x 12
D
S.S = D x RPM
12
RPM = SS x 12
D
D = C.S. x 12
RPM x
CS-7
Cutting Speeds
(Calculating -- RPM's)
Calculate the revolutions per minute for the following machining jobs and select an available
machine tool RPM from the list. (Please calculate both Rough and Finish Cuts)
Machine tool revolutions per minute available;
48
68
88
116
140
180
225
260
300
385
560
665
790
928
1087 1492 2400 3100 4300 6000
Finish
Rough
Tool
Material
Work
Material
Work
Dia.
Carbide
Cast Iron
2.00
HSS
StainlessSteel 1.500
HSS
Malleable
Iron
1/2"
Carbide
Copper
5/8"
Carbide
Brass
1.300
HSS
Bronze
7/8"
Carbide
Aluminum
2.25
HSS
Magnesium
2.250
HSS
1050 c.s.
1.250
Recommended
SFPM
492
Finish
Rough
RPM
From above list
CS-7 Q1
Cutting Speeds
Cutting Speed Quiz
1. How many RPM's are required to turn a gear blank 4.5" in diameter at a cutting speed of 42 FPM?
2. A piece of Tool Steel, 3/4" in diameter is turned in a lathe.
How many RPM's are necessary if the cutting speed is 30 FPM?
3. If turning a Cast Iron Pulley, 14" in diameter.
what RPM's are necessary using a cutting speed of 46 FPM?
4. It is desired to turn a 3/8" diameter screw at 70 FPM.
Then a thread is to be chased at 20 FPM.
Find the turning RPM and the threading RPM.
6. Find the Revolutions Per Minute for the following;
(A) Drill a 3/16" diameter hole in brass.
(B) Bore a 2 1/4" hole in aluminum.
(C) Mill the surface of low carbon steel with a 3/4" end mill.
(D) Turn a 2" diameter workpiece made from cast iron material.
(E) Chase a 1/2-13 thread on stainless steel using a single point threading tool.