July/August 2017 - Preventing toolholder deformation can increase productivity, says JP Performance Products President John Stoneback (pictured)
Q: What is toolholder deformation?
John Stoneback: A workhorse in today’s high-speed CNC machining centers, the retention knob and its relationship with V-flange toolholders can cause critical productivity issues for manufacturers due to toolholder expansion. Once expansion occurs, the holder will not pull all the way into the spindle and the toolholder typically cannot make contact with more than 70 percent of the spindle surface.
Insufficient holding by toolholders is far more typical in machining center processes than most shops realize—whether you are running one mill or hundreds. Loose tools present myriad issues industrywide in terms of production, time and tooling. Key productivity variables include chatter and vibration, excessive runout, lengthy finishing and polishing times, long setup times, rigidity issues, poor tolerances, lack of repeatability, shortened tool life, slow speeds and feeds, and shallow depth of cuts.
At the core of this quandary is what happens to the toolholders when they are tightened. Overtightening the retention knob can produce a bulge in the narrow end of the holder. This often results in the toolholder losing the shape that matches the cone of the spindle—rendering it free and seating insecurely in the machine. Tight tolerances are essential in high-speed machining, and if the toolholder doesn’t fit the spindle precisely, decreased productivity and reduced tool life are inevitable.
Q: how can high-torque tolerance solve this problem?
Stoneback: Whereas the retention knob is an unmistakably critical component of the machining process, conventional retention knobs, when installed in a toolholder, may deform the precision taper because of the elastic nature of a toolholder’s thin walls. This taper deformation prevents a toolholder from properly mating with the spindle of a CNC machine.
JM Performance Products Inc., a manufacturer of CNC mill spindle optimization products since 1966, has been spearheading the charge to overcome this manufacturing bind with its high-torque or lower-deformation retention knobs. An essential element of the patented design is a knob that is longer and reaches deeper into the holder’s threaded bore. As a result, all thread engagement occurs in a region of the toolholder where the diameter is large and where there is more material to resist deformation.
Q: What are the key design elements of a high-torque knob?
Stoneback: Essential design elements of JMPP’s patented high-torque retention knob include the following:
• Longer than traditional retention knobs
• Precision pilot increases rigidity
• Relief below the flange forces threads into a deeper cross section of the toolholder
• Hard turned to ensure precision fit and balance for high-speed operations
• Head dimensions that match existing toolholders.
When properly installed with a retention knob socket and torque wrench, this design prevents toolholder deformation. The accumulated synergistic effect of these design elements eliminates the expansion or distortion of the small end of the tool holder, allowing CNC routers to run faster.
Q: How can switching knobs stimulate reshoring in the United States?
Stoneback: Over 750,000 CNC mills have been put into service in the past 15 years in the United States. The fact is, many toolholders will expand when a traditional retention knob is installed. As more end users begin to understand the retention knob’s critical role as the interface between the toolholder and machine spindle, they will progressively move toward converting to the high-torque retention knob.
Typical CNC milling centers are running 20 percent to 40 percent slower than they should. If you are able to significantly increase the speed of machines by eliminating the deficiencies of conventional retention knobs, conservative estimate savings of 10 percent to 15 percent can be achieved.
Many larger manufacturing entities and market applications—automotive, aerospace, medical, etc.—have been implementing JMPP’s patented high-torque retention knobs and have seen tremendous productivity results. Many machine operators are not aware they can achieve significant increases in tool life, production rates and revenue by simply minimizing the expansion/deformation that happens at the small end of the taper when it is over-torqued. These are goals that are easily in reach and present U.S. machine tool die/milling manufacturers with a unique opportunity to promote reshoring.
JM Performance Products Inc.
Fairport Harbor, Ohio
440/357-1234
