TECHNICAL DATA
Milling Cutters & End Mills

Starting Peripheral
Cutting
Feeds
Speeds, Feeds & Power Calcs
Troubles & Corrective Measures
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Starting Peripheral

Speeds and feeds are the most important factors to consider for best results in milling. Improper feeds and speeds often cause low production, poor work quality and unnecessary wear to the cutter.

This section covers the basic principles of speed and feed selection for milling cutters and end mills. It will serve as a guide in setting up new milling jobs.

Speeds

In milling, speed is measured in peripheral feet per minute, (revolutions per minute times cutter circumference in feet). This is frequently referred to as a "peripheral speed," "cutting speed," or "surface speed."

The figures given in Table 1 are suggested starting speeds only. They are based on cutting conditions. For example:

Use Lower Speed Ranges for
Hard materials Heavy cuts
Tough materials Minimum tool wear
Abrasive materials Maximum cutter life

Use Higher Speed Ranges for:
Softer materials Frail work pieces or set-ups
Better finishes Hand feed operations
Smaller diameter cutters Maximum production rates
Light cuts Non-metallics

Table 1 - Starting Peripheral Speeds

WORK MATERIAL TOOL MATERIAL WORK MATERIAL TOOL MATERIAL
High Speed
Steel
Cemented
Carbide
High Speed
Steel
Cemented
Carbide
Magnesium 600 up 1000 up Titanium:    
Aluminum 600 up 1000 up Under 100,000 PSI 35 -55 150 -180
Copper 300 up 1000 up 100,000 to 135,000 PSI 25 - 35 120 -150
Brass 300 800 135,000 PSI & Over 15 -25 80 -120
Bronze 200 400 High Tensile Steels:    
Malleable Iron 100 350 180,000 - 220,000 PSI 25 -40 200 -250
Cast Iron 100 300 220,000 - 260,000 PSI 10 -25 110 -200
Cast Steel 70 200 260,000 - 300,000 PSI 6 -10 90 -180
Steel -100 Brinell 150 450 High Temperature Alloys:    
Steel -200 Brinell 70 350 Ferritic Low Alloys 40 -60 150 -300
Steel -300 Brinell 40 200 Austenitic Alloys 20 -30 100 -235
Steel -400 Brinell 20 100 Nickel Base Alloys 5 -20 50 -150
Steel -500 Brinell 10 75 Cobalt Base Alloys 5 -10 50 -100
Stainless Steel:        
Free Machining 70 400    
Other 40 300    
NON-METALLICS: These materials are so numerous and varied that specific recommendations cannot be made. In general, the use of cemented carbide at high peripheral speeds is recommended.
Feeds
CHIP THICKNESS - Chip thickness is one of the more important factors affecting tool life in milling operations. Very thin, or feather-edge chips dull cutting edges more rapidly than thick chips. Chip thickness is governed by the size and shape of the cutter and work piece. Chip thickness is affected by the feed per tooth. Figures 3 - 6 illustrate the relation of chip thickness to feed per tooth, for several conditions. It emphasizes that careful thought must be given to feed per tooth, to cutter size and design and relative location to the work.