Highlights

One of the most common turning applications is the boring of components, a function also known as internal turning. The most widespread tools used for this type of machining operation are boring bars.
ISCAR currently offers a wide range of steel and solid carbide bars that carry various insert geometries for different internal turning applications.
When selecting a boring bar for internal turning operations, the depth of the machined hole vs. its diameter and the material type influences the choice of the tool.
Large L/D ratios may cause tool deflection and vibrations, influencing the obtained accuracy and surface finish.



In order to cover the complete range of applications for internal turning, ISCAR has developed a comprehensive series of high-quality internal boring bars for different insert geometries, covering all machining applications from 4xD to 10xBD.

ISCAR offers three types of boring bars: solid steel, solid carbide and anti-vibration.
The maximum overhang for solid steel boring bars is up to 4xBD. This limitation is due to the fact that machining with a longer length of steel shank (more than 4xBD) can induce unwelcome vibrations due to the elasticity and characteristics of the steel.
In order to limit the vibration on a higher overhang of more than 4xBD and up to 6xBD, the use of solid carbide boring bars is recommended. Solid carbide boring bars represent an excellent, highly efficient option for boring applications of up to six times the tool’s machining depth. This capability is attributable to solid carbide possessing a coefficient of elasticity that is three times higher than that of steel.

However, when the machining of high overhangs of more than 6xBD is required, even the use of a solid carbide shank can cause vibrations. Therefore, in these cases the use of solid carbide can be somewhat limited.

Boring Bar Selection Guide According to Overhang to Bar Diameter Ratio


Deep turning
Deep turning solutions for machining high depth to diameter internal applications include special anti-vibration boring bar systems with a ‘live’ vibration dampening system located inside the tool body.

A product of ISCAR’s prolific RWHISPER department, innovative WHISPERLINE anti-vibration boring bars have been designed to significantly reduce and even totally eliminate vibrations when working with a high overhang from 7xBD to 14xBD.
Situated inside these ingenious tools is a unique damping mechanism that consists of a heavy mass that is supported by a rubber spring element containing oil to increase the required dampening effect.

In addition, the system contains other elements which help to further reduce vibrations. The reactive damping mechanism comes into action during machining with high overhang work depths and acts as an effective counter to vibrations.

The highly effective, anti-vibration damper effect is applicable for large D.O.C and high feed rates, and ensures continuous, efficient machining. ISCAR’s inspired WHISPERLINE anti-vibration tools considerably improve machining stability and enhance insert life. These factors enable meaningful increases in productivity to be achieved, improvements in surface quality on high overhangs to be attained, scrap levels to be reduced and users’ profitability to be enhanced.
WHISPERLINE anti-vibration tools enable the delivery of internal coolant to be supplied directly to where it is required - the insert’s cutting edge. The efficient distribution of coolant increases the insert’s tool life by reducing temperature and also improves chip control and chip evacuation.



The WHISPERLINE anti-vibration turning tool line enables the fitting of a wide range of cutting heads with a range of different insert geometries, including all ISCAR standard ISO turning inserts for different applications; thus offering great flexibility.



The WHISPERLINE boring bars represent a cost-effective, modular system with a wide range of standard shanks with diameters of 16, 20, 25, 32, 40, 50 and 60mm. The flexible boring bars are able to carry eight different interchangeable boring heads: CCMT, VCMT, DCMT, DNMG, and VNMG.

Insert geometry

Correct insert geometry is a very important factor when using anti-vibration boring bars. The most recommended insert geometry for successful anti-vibration use is a positive geometry insert with a positive rake angle, as this shape exerts a lower tangential cutting force when machining.

Choosing the appropriate nose radius of the insert is also a vitally important consideration. A lower nose radius is recommended as this configuration significantly reduces the cutting forces, due to the lower contact between the insert and workpiece, which helps to limit and reduce vibration.
A greater nose radius creates much larger radial and tangential cutting forces that can produce unwelcome vibrations.


Inserts with the benefit of appropriate chip breakers are recommended for improved chip evacuation, as the production of long and curled chips can cause a range of problems when working with long overhang tools. In addition to increasing vibration during machining, long and curled chips are liable to spoil or damage the surface quality of the workpiece. Highly recommended ISCAR chip breakers for anti-vibration tools are the F3P/F3M for finish machining applications using a small D.O.C.; and the M3P/M3M, for medium applications.

These highly-efficient chip breakers ensure excellent chip control and the creation of small chips which can be evacuated more easily with the help of the coolant supply.

An important factor in reducing vibrations is ensuring the clamping stability of the anti-vibration boring bar. Secure clamping helps users to achieve the correct workpiece dimension, which results in excellent workpiece surface quantity and assists in avoiding vibrations; clamping length should be 4XBD.

Clamping of WHISPERLINE anti-vibration boring bar