Speeds

Speeds

The speed of a drill is usually measured in terms of the rate at which the outside or periphery of the tool moves in relation to the work being drilled. The common term for this is “Surface Feet Per Minute”, abbreviated to sfm. The relation of sfm and Revolutions Per Minute, or rpm, is indicated by the following formulas:

sfm = .26 x rpm x Drill Diameter in Inches
rpm = 3.8 x sfm / Drill Diameter in Inches
In general, when operating a drill at a speed anywhere within its range for the particular material involved, reductions in speed result in more holes before regrinding is necessary. On every job there is a problem of choosing a speed which will permit the most economical rate of production which is also determined by drill costs, pieces produced in a given time and down-time for tool changing. The most economical speed for operating a drill will depend on many variables, some of which are:

 

1. Composition and hardness of material
2. Depth of hole
3. Efficiency of cutting fluid
4. Type and condition of drilling machine
5. Quality of holes desired
6. Difficulty of set-up

Speeds shown in the table below include a range in feet-per-minute. On most jobs, it is usually better to start with a slower speed and build up to the maximum after trials indicate the job can run faster.

 

MaterialSpeed in feet per minute (fpm)
Aluminum and its Alloys200 – 300
Brass and Bronze (ordinary)150 – 300
Bronze (High Tensile)70 – 150
Die Castings (Zinc Base)300 – 400
High Temperature Alloys (Solution Treated)
Cobalt Base: HS25, S816, V36
Iron Base: INCO 800, A286, N155
Nickel Base: INCONEL 700, U500, Rene41
10 – 20
10 – 20
7 – 15
Iron Cast (soft)
Cast (medium hard)
Hard Chilled
Malleable
75 – 125
50 – 100
10 – 20
80 – 90
Magnesium and its Alloys250 – 400
Monel Metal or High-Nickel Steel30 – 50
Plastics or Similar Materials (Bakelite)100 – 300
Steel-Mild – .2 to .3 carbon
Steel – .4 to .5 carbon
Tool – 1.2 carbon
Forgings
Alloy-300 to 400 Brinell
High Tensile (Heat Treated)
35 to 40 Rockwell C
40 to 45 Rockwell C
45 to 50 Rockwell C
50 to 55 Rockwell C
Maraging (Heat Treated)
(Annealed)
80 – 110
70 – 80
50 – 60
40 – 50
20 – 30
30 – 40
25 – 35
15 – 25
7 – 15
7 – 20
40 – 55
Stainless Steel
Free Machining Group: 303, 303SE, 430F, 416F, 42OF
Chromium-Nickel Group (Non-Hardenable):
(300 Series) (1) (400 Series) (2)
Straight Chromium Group (Heat Treated): (400 Series) (3)
30 – 100
20 – 60
10 – 30
Titanium Alloys,
Commercially Pure
50 – 60
5AI-2Sn, 8AI-1 Mo-1 V (Annealed)30 – 40
2 Fe-2Cr-Mo (Annealed)30 – 40
6AI-4V, 4AI-4Mn, 7AI-4Mo (Annealed)25 – 35
6AI-4V, 4AI-4Mn, 7AI-4Mo (Solution Treated & Aged)15 – 20
2Fe-2Cr-2Mo (Solution Treated & Aged)15 – 20
Wood300 – 400
(1)Austenitic (2) Ferritic (3) Martensitic

 

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