Selection of Insert

Insert selection is mainly based on the characteristics of
the insert and the requirements of the application.
Performance aspects and cost considerations should be
taken into account in the selection process together with
the cutting material grade.

Insert Shape

In general, insert with larger included angles should
be preferred to those with smaller angles in the following
order:

S(90⁰) ¨ C and W (80⁰) ¨ T (60⁰) ¨ D (55⁰) ¨ V (35⁰)

where applicable, the trigon shape W (80⁰) should be
preferred to the C insert, as more cutting edges are
available. Round inserts are an alternative to S inserts and
may also be suitable for use in form turning.

Negative-rake inserts which are usable on both sides
are more cost-effective than one-sided positive-rake
inserts.

Positive rake inserts offer advantages in I.D. turning
operations and for thin-walled parts and soft work materials

Cutting edge length

The size of an indexable insert is governed by the maximum
depth of cut d, the approach angle x_r, insert shape and
geometry .

I_e =    d         where
        sin x_r
d = depth of cut
l_e =  effective cutting edge length (width of cut)
l  = insert cutting edge length
x_r = approach angle

With approach angles from 75⁰ ~ 105⁰ the effective cutting
edge length is roughly equal to the maximum depth of cut.
In outward facing, particularly form turning (copying), the
effective approach angle is reduced . Because of the lower
thickness of cut, it is possible to use greater cutting edge
length than stated.

Cutting edge length/effective length