Page 146 - Threading_Handbook

THREAD TURNING The key cutting parameters in threading are cutting speed (Vc) and feed per revolution (f). If
2.15 Cutting Conditions

feed per revolution (f) is a constant value equal to the threading pitch, then the cutting speed
(Vc) is affected by various factors.

It should be noted that a harder carbide grade has higher wear resistance and enables
higher cutting speed, and a tougher carbide grade with its better impact strength is intended
for lower speed but enables higher feed.
There is also a relationship between insert tool life and cutting speed, which roughly be
described in accordance with the chart below.

Tool Life

Cutting Speed

This graph represents the most reasonable cutting speeds.
The velocities at the high and low ranges do not necessary exhibit the same relationship
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 in
its machinability (for example, machining threading in a tool steel will be with different cutting
conditions for annealed, pre-hardened and hardened). Therefore, a specific force needed to
remove a unit of a chip section, and load acting on an insert, differ too.

The threading tool body is also important. A durable design of the body, position of the
insert into the tool, and a reliable insert clamping method ensure machining under high
cutting data.

Other limitations such as unstable machining conditions and large overhang, improper
workpiece clamping, machine axis backlash, workpiece with a thin wall, and varied hardness
of workpieces, can lead to decreasing the cutting speed.

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.

146 ISCAR