Retention Knobs Cut Down on Toolholder Expansion

Eastec 2019: JM Performance Products’ high-torque retention knobs are designed to eliminate toolholder expansion, which causes vibration, chatter, run-out, poor finishes and poor tolerances.


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JM Performance Products Inc.’s high-torque retention knobs are designed to eliminate toolholder expansion, which can cause vibration, chatter, runout, poor finishes and poor tolerances in CNC milling. The knob design incorporates a relief beneath the pilot and reaches deeper into the thicker cross-section of the holder’s threaded bore. As a result, all thread engagement is said to occur in a region of the toolholder where the thicker cross-section resists deformation. 

The knobs are hard turned to ensure their fit and are balanced with threads cut to start and finish 180 degrees from each other. The company says that the knobs improve tool performance, even in harsh environments, increase tool life by at least 20 percent, improve finishes, shorten cycle times, and increase productivity.


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  • The Knob Problem

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  • The Real Cost Of Runout

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