Sandvik Coromant Parting and grooving - users guide - Manual (Page 42)

40
Internal grooving
Many components have an internal groove, most of them
are close to the entrance into the hole e.g circlip grooves.
The most common method to produce internal grooves is
by radial grooving but also multiple grooving and plunge
turning can be used, see page 30.
CoroCut with dedicated geometries GF, GM, TF and TM
to be used for internal operations. For small diameter bores
down to 12 mm, the Q-Cut 151.3 with geometry 4G can be used.
The CoroCut MB is available in solid steel and solid carbide bars for better stability in
longer overhangs. The precision grooving insert is available in widths from 0.7–3 mm.
For real small diameters 4.2 mm, the CoroTurn XS system has insert widths in the range of
0.78–2 mm.
During chip evacuation there is a large risk of chip jamming resulting in tool breakage,
especially when grooving into small holes. The chips have to be removed from the groove,
change direction 90°, pass the side of the toolholder and finally removed from the hole. For
secure chip evacuation, it is necessary to have a large deviation between hole diameter and
bar diameter hence a small diameter bar is the best option. Unfortunately there is a high risk
of vibration with small diameter bars.
Stability is the key to avoid vibration and this is related to the tool overhang and how far
into the hole the groove is machined. The risk of vibration is avoided by using the largest
bar size possible, while chip chip jamming avoidance call for the opposite.
The overhang should not exceed 3 x D for solid steel and 5 x D for solid carbide boring bars.
With damped boring bars it is possible to cut with overhang up to 5 x D and with a carbide
reinforced damped bar up to 7 x D.
Carbide reinforced damped bars
dm
m
dm
m
dm
m
Damped and carbide bars
Solid steel bars
L < 7 x dm
m
L ≤ 5 x dmm
L ≤ 3 x dm
m
Use EasyFix clamping sleeves for accurate
machining with less vibration and precise
height.