Ta k a m a z R Y U - G I
Here, we introduce the knowledge and various knowledge
about the product TAKAMAZ a variety of machine tools.
I hope you will help the daily work of customers.

The 13th Improved Chip Processing with a Unique Boring Bar

In boring cut, poor chip ejection
results to abnormal insert
damage,poor dimensional accuracy
and surface roughness due to chip
jamming.We will now introduce
to you a cutting example usinga unique boring bar with chip
removal.

Figure 2.

S um m ary
With cutting materials where chip processing isproblematic such as cold-forged items (un-annealed),
it is thought that boring bars with extremely
thick shank diameters are to be used to suppress
waviness during deep bore cutting process.However,
the gap between the cutting diameter and the boringbar becomes smaller, eliminating the discharge
space for the chips generated. This leads toproblems such as abnormal insert damage and poor
roughness, etc., due to chip jamming. For thisreason, measures have been taken through machining
methods such as step operations for purposes ofchip breakage,but these increase the cutting times,
and degrade cutting efficiency.Although countermeasures
such as chip breakers are adopted in chip processing,chip breaking is not easy unless the machinedmaterial is characterized by being extremely soft,and simply changing the inserts has not been apermanent solution.

Appended

figure2

Evaluation Result
Figure 2 shows Evaluation Result.
You must pay attention to the content shown in
Table 2 in boring work with difficult chip processing,such as for cold-forged items.
Figure 1.
Material

SCM415Formed Material

Cold-forged Material *No hot rolling
NoneTrial, Test

Pre-Cutting Heat Treatment
Cutting Purpose

φ12E valu ation C ontent

Chip Ejection Shaped
Unique Boring Bar

φ12By partially cutting of the end top face of aboring bar, we made a unique shaped boring barthat allows chips
to flow forward. We thenmade a comparison with conventional boring bar.
The Unique Boring Bar currently used was madeso as not to lose rigidity, the shank is ultra-hard,
and the end is made of steel. (Brazed) The cutting
piece and the cutting locations are shown inFigure 1. The tools and cutting conditions used
are shown in Table 1, and the details of the tool
shape, etc., are shown in the figure annexed toTable 1.

85

Conventional Standard
Carbide Boring Bar

Summary
By using a unique boring bar that allows chipejection, abnormal insert damage due to chip
jamming disappears during boring cut, and thisresults to the stabilization of the dimensional
accuracy and surface roughness. In addition,
the step cut for chip breaking of the conventional
methods becomes unnecessary, shortening cutting
times, and raising the cutting efficiency.
Please take note of the content shown in Table 1in boring cut with difficult chip processing,such as for cold-forged items.
Table 1
During cutting, as much as possible, cutting oil should be discharged
at sufficient pressure from inside the shaft ejecting the chips at
the front side.
The protruding amount of the bar must have some allowance so thatthe chips eject in the forward direction. (To a degree that does not
lose its rigidity)
During insert selection, select one with good chip processing properties,
and set suitable cutting conditions while observing the machining
chip state.
If a chip-ejecting shape is adopted, an extremely-thick shank diameterand ultra-hard shank is needed so as not to lose rigidity.
There is also a method where the chip ejection direction forcibly ejects
to the inside rather than to the front as in the present example.
This option must be selected according to the cutting environment andconditions.