Sandvik Coromant Heat resistant super alloys - Manual (Page 94)

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Helix angle
An end mill’s helix angle is defined as the
angle of the cutting edge relative to the
centreline of the tool. The helix influences
tool performance mainly by affecting chip
flow and cutting forces by determining the
length of engagement of the cutting edge
for a given depth of cut.
The greater the helix angle, the longer the
cutting edge length allowing longer tool life
and also giving a more gradual entry and
exit into and from the workpiece. This low-
ers the radial forces that want to push the
end mill and workpiece away from each
other.
The result is a smoother machining action
with less deflection. In most cases, high
helix is recommended for finishing opera-
tions and a low helix in roughing because of
the added strength.
A 50 degree helix is optimally suited for
milling in Inconel when radial cuts (a
e
) are
less than 20% of the cutter diameter D
c
, for
example trochoidal, slicing and finishing.
30° 45° 60°
Helix
angle
θ = 30°
θ = 50°
D
c
= 12 mm
θ = 30°
LCE = 37 mm
D
c
= 12 mm
θ = 50°
LCE = 49 mm
θ = 40° θ = 60°
LCE
LCE
π D π D
The diagram shows increased length of
cutting edge (LCE) as the helix angle
increases.
A high helix angle increases the tendency
for the cutter to pull itself out of the chuck.
A CoroGrip power chuck or shrink fit are
required to resist this.