8/23/2017 | 1 MINUTE READ

Making Tooling More Cost Effective

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Something as simple as trading standard retention knobs for a longer version could help eliminate bulge in V-flange tooling and the problems associated with it.


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Hansen Engineering Co. used a standard retention knob in the toolholder on the left. Taper deformation prevents the toolholder from properly mating with the CNC machine’s spindle, however. In contrast, the photo on the right shows use of JM Performance Products’ high-torque retention knobs in the toolholder. A longer design enables the knob to reach deeper into the holder’s threaded bore, improving taper-contact quality.

When a standard retention knob is installed in a V-flange toolholder, pressure exerted by thread engagement, coupled with the elastic properties of the steel used to manufacture the toolholdrers, creates a bulge at the small end of the holder. Once expansion occurs, the holder will not pull all the way into the spindle, and the toolholder cannot make contact with upwards of 70 percent of the spindle surface. When this happens, vibration, chatter, poor tolerances, non-repeatability, poor finishes and shortened tool life are among some of the problems that shops can face.

Hansen Engineering Co. knows these problems all too well, as its everyday machining operations began to present increased issues. A simple solution that reportedly increased the aerospace engineering shop’s productivity by 15 percent and decreased downtime was a high-torque retention knob from JM Performance Products Inc.  The high-torque knobs are longer and reach deeper into the holder’s threaded bore than standard knobs, which encourages thread engagement to occur in a region of the toolholder where there is a thicker cross section of material to resist deformation.

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    Angle heads can enable a three-axis machine tool to be more versatile. That said, this shop explains that there’s more to getting started using them than simply loading them into a machine’s spindle.

  • The Humble Pull Stud

    I’ve said that the toolholder is the least appreciated element in many milling processes, but the pull stud (or retention knob) is perhaps the least appreciated component of the toolholder.

  • The Knob Problem

    The retention knob is an unmistakably critical component of the machining process. However, the tightening of the knob itself can lead to the toolholder not seating securely in the machine. You may be losing tool life to knob tightness without even knowing it.

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