MACHINING CENTERS
CNC
machining centers have become the prime machine tool in job shops and
production plants, and are widely used in automotive manufacturing because of
their control capabilities, versatility, and agility. Many operations usually
assigned to transfer-type-dedicated equipment are now increasingly performed by
CNC machining centers – many with high-speed spindles. This shift brings into
focus the important productivity potential of CNC-dependent combination cutting
tools – tools that exploit the CNC capabilities for helical interpolation to
perform in a single operation what would otherwise require individual
operations.
With
the control capabilities that come with today’s CNC technology, it is possible
to combine drilling, threading, and chamfering into a single operation by using
specially designed cutting tools. There are many ways to make a threaded hole,
but on a CNC machining center, one option is to use a combination tool that not
only cuts threads, but also drills and chamfers the hole at the same time.
The
Thriller tool, developed by Turchan Technologies, is a good example of such an
unusual and interesting tool, Fig. 3-4-2. This tool performs in a single
operation what conventional methods usually require a drill, chamfering tool,
and tap or thread mill. Therefore the combination tool reduces the number of
tools, toolholders, and tool positioning required and it eliminates at least
two tool changes between operations. Properly applied, the result is a
significant cost and time savings, together with improved thread quality in
many cases.
Fig. 3-4-2
A variety of Thriller
combination tools that quickly and accurately produce threaded holes. (Turchan
Technologies)
HIGH SPEED MACHINING
The
Thriller Tool was developed as an enabler for complete high-speed machining of
nonferrous parts. The tool represents a step toward the same type of benefits
for drilling and threading small diameter holes as achieved in high-speed
machining operations. These operations have been hindered in the past by the
limited availability of spindles with sufficient r/min to run them at milling
surface speeds, where the full benefits of highspeed adiabatic (closed
thermodynamic system) cutting can be realized. Moreover, even the high-speed
spindles capable of such speeds do not have sufficient torque to tap holes. The
Thriller tool relieves these problems, because it never has to stop or reverse.
THRILLER TOOL DESCRIPTION
The
unique features that make the Thriller tool so effective are contained in its
construction, Fig. 3-4-3.
Fig. 3-4-3
The construction and specifications
of a Thriller tool. (Turchan Technologies)
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The
entire tool (L1) is made of solid micrograin carbide.
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Two
helical flutes are cut along the length of the threaded section (L3).
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Both
sides of the flutes are sharp to allow for the cutting of right- or
left-hand thread forms.
-
The
body (L1) contains a series of circular thread forms cut around the
circumference to the shape and pitch of the thread to be produced.
-
The
end portion is a short drill (approximately 2 thread pitches long) about
the tap-drill size of the thread with a 140° point. This part produces the
core diameter of the hole.
-
A
standard Thriller tool has 45° chamfer at the top end of the threaded
portion (D4). Other tools can be made to order to spotface, back chamfer,
or back spotface.
Thriller
tools are stocked in standard inch and metric size tools, coated tools, as well
as coolant-fed tools. They are currently available in micrograin carbide in
sizes from about 1/8 to 3/4 in. diameter. In a parallel development, Turchan is
also developing a line of small-diameter thread mills.