Recommended Cutting Speeds For HSS Drills

Drill Speed is measured by the rate at which the outside diameter of the tool moves in relation to the work piece. This speed is known as Surface Feet Per Minute (SFM) and is shown in the table below. The formula used to convert SFM to Revolutions Per Minute (RPM) is:

RPM = 3.82 X          SFM         
  Drill Diam (Inch)

The speeds shown in this table are a generalization and it is recommended that the user start at the lower end of the range and build up to the maximum after trial indicates this is possible.

Fractional Size
Number Size
Letter Size

Material
Hardness BHN
Speed SFM
Speed RPM
Steel
Magnetic Soft
<120
92-115
Structural
<200
72-92
Plain Carbon
<250
60-72
Alloyed
<250
40-60
Alloyed (Hardened & Tempered)
250-350
32-50
Alloyed (Hardened & Tempered)
>350
16-22
Stainless Steel
Free Machining
<250
40-60
Austenitic
<250
22-32
Ferritic Austenitic
<300
32-50
Cast Iron
Lamellar Graphite
<150
72-92
Lamellar Graphite
150-300
60-72
Nodular Graphite (Malleable)
<200
50-65
Nodular Graphite (Malleable)
200-300
40-60
Titanium
Unalloyed
<200
60-72
Alloyed
<270
32-50
Alloyed
270-350
22-32
Nickel
Unalloyed
<150
22-32
Alloyed
>270
14-16
Alloyed
270-350
10-14
Copper
Unalloyed
<100
82-105
Brass - Bronze
<200
92-115
Brass
<200
82-105
Bronze High Strength
<470
50-65
Aluminum - Magnesium
Unalloyed
<100
92-250
Silicon Alloyed < 5%
<150
92-250
Silicon Alloyed > 5 < 10%
<120
72-92
Silicon Alloyed > 10%
<120
60-72
Plastic
Thermoplastic
-
92-115
Thermosetting
-
72-92

Recommended Feeds For Drilling

Drill Diameter
Feed (Inch/Revolution)
1/16 - 3/32
1/8 - 5/32
3/16 - 7/32
1/4 - 5/16
3/8 - 7/16
1/2 - 9/16
5/8 - 3/4
7/8 - 1"
1-1/8 - 1-1/4
1-3/8 - 1-1/2
1-1/2 - 2"
.001 - .003
.002 - .005
.003 - .006
.004 - .008
.005 - .010
.007 - .012
.010 - .015
.015 - .020
.017 - .022
.019 - .024
.020 - .025

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