Cutting Speeds

Material Cutting Speeds

Recommended Cutting Speeds using High-Speed Steel Tools.
For Reamers use 1/2 to 2/3 speed given in this Table.
For Carbide tools double the speeds.

Material

Hardness,
Bhn

Cutting
Speed,
sfpm

Material

Hardness,
Bhn

Cutting
Speed,
sfpm

Carbon Steel
AISI-1019, 1020, 1030,
1050, 1060, 1070, 1090

Alloy Steel
AISI-1320, 3120, 4012,
4120, 4720, 4820, 5020,
6120, 8720, 9315, etal

Stainless Steel
Standard
  Austenitic (annealed)
  Cold-Drawn
  Ferritic
  Martensitic (annealed)

  Tempered

Free Machining
  Austenitic (annealed)
  Cold-Drawn
  Ferritic
  Martensitic (annealed)

  Tempered

120-150
150-170
170-190
190-220
220-280
280-350
350-425

125-175
175-225
225-275
275-325
325-375
375-425

135-185
225-275
135-185
135-175

175-225
275-325
375-425

135-185
225-275
135-185
135-185

275-325
375-425

80-120
70-90
60-80
50-70
40-50
30-40
15-30

60-80
50-70
45-60
35-55
30-40
15-30

40-50
30-40
50-60
55-70

50-60
30-40
15-30

80-100
60-90
100-120
100-130

50-60
30-40

Tool Steel
Water Hardening
Cold Work
Shock Resisting
Mold
High-Speed Steel

Gray Cast-Iron

Malleable Iron
Ferritic
Pearlitic

Bearing Bronze

Brass & Bronze

Aluminum
Cast
Heat Treated
Wrought Cold Drawn
Wrought Heat Treated

Plastics

150-250
200-250
175-225
100-200
200-250
250-275

110-140
150-190
190-220
220-260
260-320

110-160
160-200
200-240
240-280

70-80
20-40
40-50
50-70
30-40
15-30

90-140
80-100
60-80
50-70
30-40

120-140
90-110
60-90
50-60

30-100

150-300

200-300
150-250
150-300
140-300

600-1000

stolen from http://its.foxvalley.tec.wi.us/MachShop1/drillpress/cutspeeds.htm

Basic Spindle RPM for Drilling and Milling

Spindle RPM for Cutter Diameter
Material	SFPM	1/8"	1/4"	1/2"	3/4"	1"	2"	3"	4"	5"	6"
Tool & SS Steel	30	900	450	220	150	110	60	40	30	45	20
Cast Steel	35	1000	530	260	180	130	70	45	33	27	22
Cast Iron	50	1500	760	380	250	190	95	64	48	38	32
Carbon Steel	60	1800	910	450	300	230	115	76	57	46	38
Mild Steel	70	2100	1000	530	350	260	130	90	67	53	44
Bronze	100	3000	1500	760	500	380	190	130	95	76	64
Brass	200	6000	3000	1500	1000	760	380	250	190	150	130
Aluminum	300	9100	4560	2280	1500	1140	570	380	280	220	190
Plastic	1000	30000	15000	7600	5000	3800	1900	1200	950	760	640

Speeds in Surface Feet per Minute are specified for High-Speed Steel drill bits, and are approximate for normal drilling operations.

Speeds should be halved when using Carbon Steel bits and can be doubled for Carbide bits. Use coolant judiciously.

For Milling operations speeds may be increased by 50%. Lathe turning speeds may be increased by 100%.

The best rule of thumb for proper cutting speed is the color of the chip when cutting steel.

Using a high-speed steel drill bit the chips should never be turning brown or blue.
Straw colored chips indicate that you are on the maximum edge of the cutting speed for your cutting conditions.
When using Carbide bits, chip colors can range from amber to blue, but never black.
A dark purple color will indicate that you are on the maximum edge of your cutting conditions.

Calculation of Spindle RPM

the formula for Spindle RPM, given Cutting Speed in feet-per-minute and Cutter Diameter in inches is:

(Cutting-speed x 12inches) / (Cutter-diameter x Pi)

Simplified Calculation of Spindle RPM

conveniently enough the above formula approximately reduces to this:

(Cutting-speed x 4) / Cutter-diameter)

Depth of Cut

FLYCUTTING -- Depth of cut on flat surfaces with H.S.S. cutters.

Mild steel -- .030 in.
Brass -- .045 in.
Alluminum -- .060 in.

END MILLING -- Spiral flute H.S.S. endmills.
Maximum depth of cut and tool offset into material when cutting along one edge.
The amount of material removed per pass is a box of this size in both directions.

Cutters up to 1/4" diameter -- 1/8 of diameter

1/8" cutter -- 1/64 or .016"
3/16" cutter -- .024"

Cutters 1/4" and over -- 1/4 of diameter

1/4" cutter -- 1/16 or .063"
1/2" cutter -- 1/8 or .125"

SLOT CUTTING -- H.S.S. spiral fluted endmills.
Incrimental depth of cut when all edges of the cutter are in contact with material.
Spindle speed should be halved from that recommended for drilling.

Slotting Depth for Cutter Diameter
Material	1/8"	3/16"	1/4"	3/8"	1/2"	5/8"	3/4"
Mild Steel	.025	.030	.045	.070	.100	.200	.250
Brass	.027	.040	.060	.100	.140	.250	.300
Aluminum	.030	.045	.065	.110	.150	.300	.350

KEYWAY CUTTING -- H.S.S. disc cutters (i.e. saw blades).

Spindle speed for Cisc Cutter Diameter
Material	2"	2.5"	3"	3.5"	4"
Mild Steel	65	55	45	38	33
Brass	115	95	75	65	55
Aluminum	190	155	125	110	95