HRC55 Golden Color 4 Flute Long Shank Square End Mill Cutter 1/4
A material like aluminum produces large chips compared to other
materials. For that reason, 4 flute end mills are rarely used with
aluminum because the flutes can get jammed with chips and break the
For harder materials, you want to use more flutes. Having more
flutes reduces chip load and improves surface finish.
While the number, direction and type of flutes that a cutting tool
has can vary widely, the tools most commonly used have two flutes
and are up-cut spirals to move the chips up out of the cut.
1. Two Flute: Has the greatest amount of flute space, allowing for more chip
carrying capacity in softer materials. Used primarily in slotting
and pocketing of non-ferrous materials like aluminum where chip
removal is a concern.
2. Three Flute: Allows for better part finish in harder materials. The three
flutes provide for greater strength and the ability to pocket and
slot both ferrous and non-ferrous materials.
3. Four Flute/Multiple Flute: Ideal for finish milling. The extra flutes allow for faster feed
rates to produce a much finer finish than two or three flute tools.
However, the reduced flute space may cause problems with chip
The most common flute numbers for general milling operations are
two (better space for chip ejection) and four (better surface
End Mill Materials
End mills are made out of either cobalt steel alloys (known as high
speed steel, or HSS), or from tungsten carbide in a cobalt lattice
(shortened to "carbide").
1. High Speed Steel (HSS): Provides good wear resistance and costs less than cobalt or
carbide end mills. HSS is used for general purpose milling of both
ferrous and nonferrous materials. While usually inexpensive, HSS
does not offer the tool life or speed advantages of cobalt and
carbide end mills.
2. Cobalt: Cobalt is an M42 tool steel with an 8% cobalt content. Cobalt is
more expensive but provides better wear resistance and toughness
than HSS (M7). Because the tool can run 10% faster than HSS, metal
removal rates and finish are better than HSS.
3. Solid Carbide: Carbide is considerably harder, more rigid, and more wear
resistant than HSS. However, carbide is brittle and tends to chip
instead of wear. Carbide is used primarily in finishing
applications. Carbide tools are best suited for shops operating
newer milling machines or machines with minimal spindle wear.
Rigidity is critical when using carbide tools. Carbide end mills
may require a premium price over the cobalt end mills, but they can
also be run at speeds 2 1/2 times faster than HSS end mills.
The choice of tool material depends on the material to be cut as
well as on the maximum spindle speed of the machine. Smaller
milling machines may not be capable of reaching the spindle speeds
recommended for carbide end mills.