Sandvik Coromant Heat resistant super alloys - Manual (Page 91)

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Down milling (climb milling). Up milling (conventional milling).
Application recommendations
Down milling
It is almost always more favourable to apply down milling rather than up milling. When the
cutting edge goes into contact in down milling, the chip thickness has its maximum value,
in up milling the chip thickness is zero.
The tool life is generally shorter in up milling due to the fact that there is considerably
more heat generated due to the rubbing action that takes place on entry. The radial forces
are also considerably higher in up milling.
Avoid excessive deflection
Shallow radial cuts (a
e
) should be applied to avoid excessive deflection of the cutting tool
and to keep a high tolerance level and geometrical accuracies on the machined compo-
nent.
It is important to use a tool with a maximum core diameter (higher bending stiffness).
l = overhang
D
c
= tool diameter
F = radial force
δ = deflection
E = modulus of rigidity of the tool
20% overhang reduction reduces tool deflection by 50%.
20% increased D
c
(10 to 12 mm) reduces tool deflection by 50%.
δ ≈
F x l 3
E x ( π x D
c
4 )