Test Findings & Conclusions
- Toolholders begin to expand when standard retention knobs are tightened to as little as 5 to 15 ft/lbs.
- The marks on the toolholder shanks result from improper fit of the toolholders in the spindles.
- Upon removal of the retention knob from the test toolholder, the test toolholder returned to its original size.
- At 40 ft/lbs, 90% of the test toolholders were six to nine times the grind limit over size.
- Testing showed that some toolholders were as high as 40 times the grind limit.
- Conclusion: Tool wear will be significant with toolholders able to move in a random pattern in the machine spindle; this movement will break the razor edge off tools.
- Conclusion: High speed tools will not fit in the spindle properly and will perform inconsistently.
- Conclusion: High speed tools are out of balance after the retention knobs are installed.
- Conclusion: Finish cuts must be slowed to allow for cutter run-out and a reduced number of teeth cutting.
- Retention knobs made by the same manufacturer did not yield consistent results.
- Toolholders made by the same manufacturer did not yield consistent results.
- Conclusion: Tools cannot be loaded into the spindle in a consistent manner resulting in difficulty holding close tolerances.
- Conclusion: ISO compliant companies need to have a procedure to insure that the toolholders used in manufacturing fit the spindle of their machines.
- J & M Machine’s high torque balanced retention knobs can be tightened to the same torque level as stardard retention knobs with two times to ten times LESS toolholder distortion.
- Conclusion: J & M’s “Taper Shank Test Fixture” should be used to insure that toolholders do not expand when retention knobs are installed.
- A 25% safety margin can be achieved by using J & M Machine’s retention knob sockets and a torque wrench to tighten the knob to 40 ft/lbs.
Retention Knob Torque Test.com 