Page 134 - TURNING CATALOG p121-254

ISOTURN INSERTS USER GUIDE

Key Points for Turning with CBN Rounding and chamfering at the ”soft” state
Rigid clamping of the workpiece and toolholder
Benefits of using CBN inserts
1 Can replace grinding operations, which reduces

machining costs.
2 Dimensional stability, which is especially important in

mass production. Minimizes the amount of scrapped parts.
3 “Green” approach, due to minimized usage of coolant.

There are a few guidelines to follow to achieve
the best results and high productivity when
machining hard materials:

• CBN is characterized by hardness of 4500 HV.
The high hardness of CBN enables it to machine
hard materials at high speeds and feeds.

• Successful HPT (Hard Part Turning) demands
not only suitable cutting tools, but also the right
conditions, preparation and environment.

• HPT begins with a correct “soft” state machining design
that will create the best possible conditions for HPT.

The “soft” state (around 20-40 HRC) is the
state in which the workpiece material is yet
to be hardened to its final hardness.

Important points when planning the
“soft” machining process:
• Avoid burrs
• Keep close dimensional tolerances
• Do not enter or exit a cut suddenly
• Enter and exit by planning radius movements
• Use wiper inserts to achieve superior surface finish
• Do not leave sharp corners (round or chamfer)
• Machine stability, rigidity and thermal stability are
vital conditions for producing a high quality finished
part. The better the stability of the overall machine
concept, the closer the tolerances will be achieved.
• Clamping the workpiece with sufficient force will prevent
its movement and improve surface finish. Make sure that
you employ wide clamping jaws which offer better grip on
the workpiece, compared to ordinary three point jaws.
• Using tailstock in long parts will add even more
stability and rigidity to the machining process.
• Large cross section tools further add to system rigidity.
• Coolant-Generally, do not use coolant when machining
hard materials. CBN inserts tolerate high cutting
temperatures, and therefore have no need for coolant.
Avoiding coolant is more economical, environmentally
friendly and better because as the material heats up
during the turning process, it becomes slightly softer
and easier to machine. However, there may be some
applications that require using coolant: in cases of
continuous turning when high surface finish is required.

Use tailstock in long parts

254 ISCAR