Page 106 - THREADING CATALOG

USER GUIDE
THREAD TURNING The key cutting parameters in threading are cutting speed • In order to produce threading with a 2 mm pitch,
Cutting Conditions

Feed (F)
(Vc) and feed per revolution (f). If feed per revolution (f)
Feed per revolution (F) always is a constant
is a constant value equal to the threading pitch, then
value that equal to the threading pitch.
the cutting speed (Vc) is affected by various factors.
For example:
It should be noted that a harder carbide grade has higher
wear resistance and enables higher cutting speed, and
the feed will be 2 mm/rev (mm per revolution).
a tougher carbide grade with its better impact strength
is intended for lower speed but enables higher feed.
be 1.8 mm/rev (mm per revolution). In this case, the
There is also a relationship between insert tool life
definition of the value of the feed per revolution (F) is
and cutting speed, which roughly be described
required to convert a value of TPI to pitch in mm, i.e.
in accordance with the chart below. • In order to produce threading with 14 TPI, the feed will
tool life 25.4

14 TPI ≈ 1.8 mm
Usable Formulas
cutting 1 inch = 25.4 mm
speed 25.4

TPI = Pitch (mm)
This graph represents the most reasonable cutting speeds.
The velocities at the high and low ranges do not Cutting Speed (Vc)
necessary exhibit the same relationship.
The starting cutting speed can be
defined as the following formula:
The machinability factor should be taken into consideration
as machinability of each engineering material is different,
and even the same material can be substantially different Vc = Ks x Vo
in its machinability (for example, machining threading
in a tool steel will be with different cutting conditions
for annealed, pre-hardened and hardened). Therefore, When
a specific force needed to remove a unit of a chip Vc — starting cutting speed
section, and load acting on an insert, differ too. Ks — stability factor
The threading tool body is also important. A Vo — basic cutting speed
durable design of the body, position of the insert
into the tool, and a reliable insert clamping method Stability Factor (Ks) is defined by the below
ensure machining under high cutting data. estimate of threading operation stability:
Other limitations such as unstable machining for normal stability: ks=1
conditions and large overhang, improper workpiece for unstable operations such as: high overhang,
clamping, machine axis backlash, workpiece with poor clamping and etc.: ks=0.7
a thin wall, and varied hardness of workpieces, • Basic cutting speed (Vo) is determined in the table below,
can lead to decreasing the cutting speed. according to carbide grade and workpiece material.
Machine tool and tool holding also represent a constraint.
Poor machine conditions and non rigid toolholders
create an additional barrier for increased cutting data.
The mentioned arguments are very general and no
doubt everyone who is involved in metal cutting
is familiar with them. They are good illustration of
complex dependence or the cutting data on different
attributes. How to go from the generalities to the
particulars and specify the starting cutting data?
The following cutting recommendations have
been developed by ISCAR specialists and
accordingly apply to ISCAR products.

ISCAR
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