This document discusses circular milling techniques. It provides information on: 1. Approaching and leaving contours in a circular motion to avoid dwell marks and achieve better circularity. 2. How the feed rate at the cutting edge is higher than the feed rate at the center of the tool for circular milling. 3. Factors that determine the maximum plunge angle for circular milling, including tool diameter and type of insert used.

1. vf [mm/min]
vfm [mm/min]
D
Vf Vf
Vfm Vfm
D
d
d
vfm = vf ––––––
D + d
D
vfm = vf ––––––
D – d
D

Tools with ISO elements | Technical appendix | Circular milling
Moving in and out
On moving in or out the contour should always be approached or
left over a quarter or semi-circle. This action will ensure tangential
plunging or removal of the tool from the workpiece.
In this way dwell marks on the workpiece are avoided and better
circularity of the part machined achieved.
Circular milling
Circular milling with two-axis feed rate
Circular milling external machining Circular milling internal machining
Feed rate at the
cutting edge
(at the contour)
Feed rate at the
centre of the tool
(at tool centre)
190

2. α
a
b
c
ø 16, ø 18 3°
ø 20 5°
ø 22, ø 25 2,5°
ø 28, ø 32 1,5°
ø 40 0,7°
ø 25 8°
ø 32 5°
ø 40 2,5°
ø 16 1,5 mm
ø 20 - ø 40 5 mm
ø 25 - ø 40 8 mm
ø 40 2,5°
ø 25 - ø 40 8 mm
2,0 1,0
3,1 1,6
4,0 2,5
α
ae
α
ae
Tools with ISO elements | Technical appendix | Circular milling
Ramp angle α:
The maximum plunge angle α is dependent on the tool.
In case of two-axis angled entry various machining
processes take place at the same time:
a) Machining at the entire periphery of the tool
(peripheral machining) with leading indexable insert
b) Machining at the face of the milling cutter with leading insert
c) Machining at the face of the milling cutter with trailing insert
Modified milling cutter type M
ICM90-B2-Shank, ICM90-B2, ISM90-B2-Shank, ISM90-B2.
If indexable inserts with a radius >1.2 mm are used, the tool body
must be reworded at the peripheral edge as per the table shown.
In this case the modified milling cutter type M can be selected
(see section Milling pages 49-53)
Alternatively the standard milling cutter can also be ordered and
re-worked by the customer.
Two axis angled entry – linear (flute)
Plunge milling Milling cutter
diameter
Indexable insert that
can be used
Maximum ramp
angle α
Type BDMT11T3
Type BDGT11T3
Type BDMT1704
Type BDGT1704
ø 50 or more Not recommended
Vertical milling Milling cutter
diameter
Indexable insert that
can be used
Max. cutting
width ae
Type BDMT11T3
Type BDGT11T3
Type BDMT11T3
Type BDGT11T3
Type BDMT1704
Type BDGT1704
Plunge milling
Milling cutter
diameter
Indexable insert that
can be used
Maximum ramp
angle α
Type BDMT1704
Type BDGT1704
ø 50 or more Not recommended
Vertical milling
Milling cutter
diameter
Indexable insert that
can be used
Maximum cutting
width ae
Type BDMT1704
Type BDGT1704
Application notes
For end milling cutter ICM90-B2-Shank
For shoulder cutter head ICM90-B2
Standard Re-worked
Indexable insert radius Radius required on the tool body
Technical
appendix
Peripheral cutting edge Face cutting edge Inner cutting edge
(trailing)
191

3. 80 4,3
100 3,4
125 2,8
140 2,4
160 2,1
80 100 125 140 160
142-160 182-200 232-250 262-280 302-320
α°

P
1
2
Tools with ISO elements | Technical appendix | Helix milling
Selection of the milling cutter diameter as a function of the size of the bore
In the case of centre-cutting milling cutters
it is important to select the correct ratio of
milling cutter diameter and bore diameter.
The insert must cut along the centre axis.
If the milling cutter diameter is too small,
there is a core in the centre.
If the milling cutter diameter is too large,
the centre is not machined. As a result a
protrusion is left. This protrusion presses
the milling cutter axially. There is a collision
between the workpiece and tool.
Helical angled entry
Helical angled entry is an alternative to drilling.
During this process a circular movement is made with
simultaneous axial feed.
Pitch (P):
The pitch (P) corresponds to the axial material removal
rate per revolution.
This aspect is dependent on the workpiece, tool length,
material and machine.
Advantages compare to circular milling
• Better circularity and concentricity
• Better cutting behaviour on applications susceptible to vibration
• Constant angled entry into the workpiece
• The milling cutter is continuously engaged, no entering or
exiting per revolution compared to circular milling
Helix milling
1 Drilling into the solid (flat bottom of the bore)
Milling cutter diameter (mm)
Bore diameter (mm)
Note:
In the case of a bore diameter between the ranges stated, for example 170 mm, the smaller milling cutter with a
diameter of 80 mm is selected. Two machining steps are then necessary to machine the bore.
2 Enlarging a bore (no face machining)
Milling cutter diameter = < 0.5 x bore diameter
Application note
Tool ø
Max. possible
plunge
angle α°
192