Page 29 - machining_titanium_05_2019

Peripheral Milling

Table 15 gives averaged values of basic feed per tooth fo and corresponding
parameters of chip thickness (hm, hmax) depending on the ratio between
ae and d and a carbide grade for peripheral milling by indexable cutters and
Table 16 – by solid carbide endmills and MULTI-MASTER heads. MILLING TITANIUM

Starting feed per tooth fz is defined by the following equations:
for 90° indexable cutters

fz=fzo×Ks (5)

- for 90° SCEM and MULTI-MASTER heads

fz=fzo×Ks×Kf (6)

Where: fzo – basic feed per tooth
Ks – stability factor
Kf – tooth-strength factor (Table 17)

The stability factor here is set as below:
• Ks=1 for normal stability
• Ks=0.8-0.85 for unstable operations (high overhang, poor tool- or workholding,
milling thin walls, etc.), and milling in unfavorable conditions.

Example
A manufacturer considers milling square shoulder by a MULTI-MASTER tool that carries
a 20 mm (0.750 in) Dia. cutting head, made from carbide grade IC308. The shoulder is
9.5 mm (0.375 in) in depth and 5 mm (0.2 in) in width. Operational stability is sufficient.
Which feed per tooth (chip load) fz should be set as starting?

ae/d=5/20=0.25. fzo=0.085 mm/tooth
(Table 16), Kf=0.94 (Table 17). Ks is assumed as 1.
fz=0.085×0.94×1=0.08 (mm/tooth) or 0.031 ipt.

The average chip thickness in this case will be 0.042×0.94=0.04 (mm) or 0.15 in,
and the maximum chip thickness – 0.073×0.94=0.068 (mm) or 0.026 in.

27